J. Physiol. (I 954) I 25,

Transcription

1 488 J. Physiol. (I 954) I 25, BEHAVIOUR OF CATS AFTER INTRAVENTRICULAR INJECTIONS OF ESERINE AND DFP BY W. FELDBERG AND S. L. SHERWOOD* From the National Institute for Medical Research, Mill Hill, London, N. W. 7 (Received 19 March 1954) In a previous paper we have described the effects of a number of drugs injected into the unanaesthetized cat through a cannula permanently implanted into the lateral cerebral ventricle (Feldberg & Sherwood, 1954). The present paper records the effects of the anticholinesterases eserine and diisopropylfluorophosphonate (DFP) administered by the same route. A few experiments were also made with large doses of acetylcholine. METHODS The method of implantation of a permanent cannula into the lateral ventricle of the cat and of injections of drugs through this cannula was the same as described in detail previously (Feldberg & Sherwood, 1953, 1954). In all cats the right lateral ventricle was cannulated. Eserine sulphate and acetylcholine dichloride were dissolved freshly for each experiment in Tyrode solution. All values refer to the salts. The dilutions of DFP in Tyrode solution were made freshly for each experiment either from a 1% stock solution of DFP in propylene glycol or from liquid DFP. The volume of injection was always ml. RESULTS Eserine By the prominence of the signs we can distinguish three stages in the effects of eserine; these overlap to some extent. The first stage is characterized by vigorous scratching, licking and washing. To these are added, a transient dilatation of the ear vessels, congestion of the tongue, peculiar mouth movements, and sometimes salivation and lachrymation. Within a few minutes of the injection the cat starts licking its lips and from time to time opens its mouth widely, revealing a congested tongue. The opening of the mouth is abrupt, its closure gentle. Visible salivation and lachrymation are seen in a few instances. Next, there is intense and frequent scratching of the head and face and the cat keeps wiping its front legs over its face and licks both front and hind legs with great vigour, sometimes carefully licking or nibbling between the fanned toes. Such scratching bouts often begin * With a personal grant from the Medical Research Council.

2 INTRAVENTRICULAR ESERINE AND DFP 489 with the characteristic mouth movements, forceful shaking of the head and twitching of the ears. The appearance is that of intense itching or irritation, especially in the face, on the head, and forelegs. At the peak of this stage this activity may continue uninterrupted for many minutes, but later on, scratching and wiping bouts occur at lengthening intervals. There is an early transient phase when the ears are warm, due to intense dilatation of the vessels. Throughout the first stage the cat is usually active, moving about swiftly. With small doses (10,ug), these effects are sometimes the sole changes noted. The second stage which is pronounced only after larger doses (20-100,g) is characterized by changes in stance, gait and posture. The movements become more sudden and abrupt, stiff and clumsy. In some cats the tone of the flexor muscles of all four legs is increased, and when the cat is induced to walk it does so in a low crouching attitude and tries to lie down after a few clumsy steps. In others, the hind legs are maintained in flexion, the front legs in extension, and even when the cat is induced to walk it tries to move without raising its hind quarters, progressing like a dog wiping its bottom on the grass. At rest there are quivering movements of the ears, head and shoulders and tremor of the leg muscles. The tendon reflexes are exaggerated. With these changes in the motor system, there are signs of laboured, sometimes quickened respiration. There is either an expiratory growl or gasps and wheezes, or both expiration and inspiration are accompanied by wheezes suggesting glottal or bronchial obstruction. During this stage the cat has the tendency to lie or sit down but will respond to most noises with quick, abrupt, small movements. The scratching and wiping bouts become less frequent. On a few occasions the animal passed faeces and urine and vomited. The motor and respiratory effects wear off after min. The third stage comprises the development of stupor with signs of catatonia. Although this change of awareness develops fully only after the other two stages and then persists for several hours, its beginning can be noted earlier. At a time when the cat still frequently scratches and licks itself, there are brief periods when its awareness seems interrupted. From time to time the cat turns its head momentarily to one side and slightly up, stopping abruptly, remaining fixed in this position and staring apparently unaware of its surroundings. This condition seems to correspond to momentary 'absences' in man. They last at first only a second or two, but later on increase to several seconds before movements are resumed and awareness of its surroundings seems re-established. Later still the cat, if left undisturbed, sits hunched up without movement; its eyes are half shut or shut and its head is slightly inclined forward. The cat responds to noises by moving its ears and sometimes also by opening its eyes. It will then follow hand movements with its eyes and head but without any other movement of the body. Sometimes

3 490 W. FELDBERG AND S. L. SHERWOOD the cat may curl up with closed eyes, giving the appearance of being asleep. If the cat is induced to walk, its movements are slow and after a few steps it sits down slowly and in stages. When picked up and dropped into its cage, the cat retains the attitude in which it landed for a minute or two and then gradually sinks down into a lying position. The cat can be passively brought into unnatural postures without much struggling. If a front leg is twisted behind its back so as to rest across the spine, the leg can be kept in this position for up to 90 sec with minimal restraint; light touch with one finger against the paw suffices. During this period the cat may once or twice make a short-lasting, feeble, and desultory attempt to restore its leg to a normal position. When the finger is removed the leg may remain in its abnormal position for sec. Whilst the leg is kept in the abnormal position in a standing cat, it remains standing on three legs without movement, staring ahead without expression and betraying no affect. The cat can be turned on its back without much struggling and remains in this position when one extended foreleg is lightly held down. It may display resentment by a plaintive growling or miaowing and whipping of its tail, but all other defence movements are abortive or absent, or alternatively it may give the appearance of being indifferent to this procedure. The cat may look at the observer for several seconds with open eyes, but they close gradually if the cat is kept in this position. Respiration is slow. When the cat is handled in this way the legs are neither flaccid nor spastic. The resistance to passive movements is uniform and does not increase with the degree of excursion of the limb. There is no feel of elasticity and no tendency of the limb to return from any excursion to the previous position. The feel of the limb is like that of 'waxy flexibility' in man. The cat is not weak, for it can be induced to walk and even jump, but then withdraws into a corner, where it remains in a sitting or lying position and closes or half closes its eyes. DFP In the earlier experiments the DFP was made up as is customary from a 1% stock solution in propylene glycol. It was found that propylene glycol in the amounts present in the injection volume had certain effects of its own which modified the action of DFP. Therefore, in later experiments the dilutions were made from the pure liquid DFP. We shall describe first the effects of these injections, then those of propylene glycol and finally those of DFP diluted from the 1% stock solution in propylene glycol. DFP diluted from liquid DFP. The doses injected were usually 100,ug and the effects were basically the same as with eserine, but signs of catatonia were more pronounced. There was again the initial stage of severe itching. One cat at the height of this effect wiped and scratched its ears and face with both forelegs simul-

4 INTRA VENTRICULAR ESERINE AND DFP 491 taneously and so forcefully that it stumbled and fell but did not stop scratching; nor did it stop after falling over the edge of a shelf. In fact it was not possible to interfere with the scratching bouts which had a paroxysmal character. As with eserine the initial stage of itching was followed, with some overlap, by increased reflex excitability and tone of the leg muscles and tremor and quivering of the ears and head. Usually the cats were lying down during this stage without relaxation of the muscles. When induced to walk the gait was spastic; sometimes the cats moved in a low crouching position but only for a few steps and then lay down again. On a few occasions the cats passed faeces and urine. The cats were agitated or frightened and were easily startled by noise or touch. Respiration was often laboured. During the third stage which developed within the first min and deepened during the following hours spontaneous general activity was reduced, the cat no longer moved about but usually stood, sat or lay where it was put. Sometimes it looked about or gazed up to the ceiling, and pricked its ears as if it were responding to a stimulus which could not be perceived by the observer. A few 'absences' were noted early. They lasted at first for a second or two but later increased in duration and frequency. The cat, when patted, or during any activity of its own, would suddenly turn its head up a little and to one side with an expressionless gaze and remain motionless apart from some quivering of the pricked ears. During -these 'absences' the cat's attention could not be obtained. The following tests were applied in this condition: (1) With the cat sitting or standing, a front paw could be abducted or extended and kept in an abnormal position without the cat making any effort to resist. When the limb was released, the cat did not return the limb to a more natural position for many seconds, or even minutes. (2) With the cat sitting or standing, a foreleg could be brought behind the cat's back without muscular resistance, so that it rested across its spine and could be kept there with barely a touch of the observer's finger apparently indefinitely. When this minimal restraint was removed the limb remained in this distorted position for 1 or 2 min. (3) When the cat was placed with its forepaws on the rungs of an inverted stool some 18 in. from the ground, the cat remained in this vertical position. The cat kept its head erect and stared ahead with wide open eyes. There was no indication of any sagging of the head or body, but the cat retained its vertical attitude stiffly for several minutes. During this time it lashed its tail and moved its ears and facial muscles. When pushed the cat could jump safely, and if sufficiently aroused by persistent stimulation, run back into the cage without signs of motor deficiency. The cat could also be suspended from a somewhat lower rung by its hind legs, across the groin, with its front legs resting on the ground, and maintain this position. In this state the cat resembled Bailey's 'catatonic' cats with mid-brain lesions. With somewhat larger doses the latency between injection and the onset of

5 492 W. FELDBERG AND S. L. SHERWOOD signs of itching was reduced to about 1 min. Further, the animals became agitated and appeared frightened: when approached they started, tended to cringe in a corner of the cage, and when touched snarled, hissed and hit out. This change in behaviour occurred within a few minutes of the injection. A further, later, sign of the larger doses was the appearance of seizure activity. For instance, in one cat, 30 min after the injection of 160,ug DFP, whisker movements previously noted became pronounced and changed into grimacing, especially affecting the labial and nasal muscles. Presently these movements became spasmodic, included the ears, and culminated in alternate twitching of the two sides of the face. The cat, which hitherto had been sitting, rose and began to circle anti-clockwise at increasing speed with jerky movements and saliva poured from its mouth. The appearance was that of the onset of a seizure. However, the cat stopped circling after about half a minute, and during the subsequent minutes seemed to react more promptly than before, and not angrily, when approached or touched. After a further 25 min, a full, symmetrical, tonic-clonic seizure developed, starting again with grimacing, circling, salivation, and fine tremor of the thigh muscles. After the seizure the cat looked about, apparently disorientated. Isolated, myoclonic contractions continued and at times increased; the danger of a further seizure was avoided by intraperitoneal injection of 1-5 ml. sodium pentobarbitone. Within a few minutes all seizure activities ceased and anaesthesia supervened. Propylene glycol. The intraventricular injection of ml. of a 4% solution of propylene glycol in Tyrode caused no detectable immediate changes in the behaviour of the cat. There were no signs of itching, motor phenomena or changes in awareness. However, after about min the cat became less lively, the movements became very slow and the animal had a tendency to sit hunched up or to lie in the cage with eyes half shut or shut. In the course of the following hour the cat might become apathetic and sluggish and its expression was one of extreme malaise. When, in this condition, an attempt was made to bring a foreleg of the sitting cat behind its back, so that it rested across its spine, there was muscular resistance which had to be overcome, but afterwards the foreleg could be kept in this abnormal position for sec if the cat was not roused, which occurred easily in response to any kind of noise in the room, or to touch. Similarly, when a foreleg was abducted in the sitting cat there was increasing resistance with the degree of excursion, but again, once the resistance was overcome, the cat, while undisturbed, retained the leg in the abducted position. In this condition it was also possible to place the forepaws of the cat on the upper rung of an inverted stool some 18 in. from the ground, and for the cat to remain in this 'standing upright' position for several minutes. There was, however, this difference from the cat when subjected to this test after DFP. The head slumped on to the rung and remained supported by it the whole time, the body sagged and the eyes were half or completely

6 INTRA VENTRICULAR ESERINE AND DFP 493 shut, giving the appearance of a very sleepy or drowsy cat. When the cat was disturbed it at once descended with very slow but fully co-ordinated movements. The condition wore off about 24-3 hr after the injection. It was noted that most cats were eating and drinking frequently before and during the development of this condition. DFP in propylene glycol. The effect differed from that of pure DFP in that the scratching and wiping during the initial stage of itching appeared somewhat reduced, that the motor phenomena of the second stage were decidedly reduced and that the third stage was a mixture of the effects seen with each drug alone; the features of 'catatonic stupor' were accentuated and modified by languor. The doses of DFP injected were usually 100,ug either divided into two doses It is interesting to note given at about 20 min intervals or in a single dose. that although propylene glycol by itself changes the behaviour of the cat only after min, it was apparently able to modify the effects of DFP at a much earlier stage. The impression was gained that with the combined drugs the first two stages were reduced and cut short by the early onset of stupor. During the condition of 'catatonic stupor' the three tests applied after the pure DFP injections showed that the cat could be kept in abnormal postures for even longer periods, for instance 10 min or longer, than after pure DFP alone. In addition, the appearance of the cat during these states was a mixture of that seen after DFP and propylene glycol given separately. For instance, when the cat was suspended with its front paws on the upper rung of the inverted stool it remained in this position with its head drooping, the eyes half shut and the body sagging a little, whereas after DFP alone the cat in this position kept its head erect and stared with eyes wide open. During this condition of deep stupor and languor the cat could also be placed with its hind and front paws at equal heights on two parallel rungs of an inverted stool or similarly on two stools placed about 2 ft. apart and it remained in this position until taken down after 10 min. With propylene glycol alone this test was negative. Whilst the cat was suspended in these tests it would lash its tail or move its ears and facial muscles but was otherwise immobile. When pushed off, however, it jumped safely and ran away at its usual speed, whereas after propylene glycol alone all movements were grossly retarded and the cat could not be made to run. A larger dose of DFP (200,ug) in propylene glycol produced, like this dose of DFP alone, general convulsions. Large doses of acetylcholine In a previous paper the effects of intraventricular injections of jg acetylcholine were described. Some of the effects seen resemble those observed with the anticholinesterases, particularly the long-lasting stupor. The

7 494 W. FELDBERG AND S. L. SHERWOOD appearance of itching, so characteristic of the initial stages of anticholinesterase action, was not noted, but from the protocols of these previous experiments it was found that scratching or washing was observed irregularly in several cats after the injection. Since this was not a regular sign, it has not been regarded as an acetylcholine effect. However, in view of the present findings with anticholinesterases and of the fact, at that time unknown to us, that intracisternal injections of acetylcholine lead to frequent scratching in cats (Koenigstein, 1951), it seems reasonable to assume that it was an effect of the injection. In order to see whether the comparison between anticholinesterase and acetylcholine effects on intraventricular injection could be advanced further, and whether the convulsions seen after intracisternal acetylcholine injections into cats by Brenner & Merritt (1942) (dose not given) could be produced by injections into the lateral ventricle, two cats were given doses of 1 mg acetylcholine by this route. In both cats general convulsions were produced after a latency of 2-3 min. These convulsions started with repeated small, quick jerks of the head and twitching of the ears and whiskers. Then the contralateral forepaw showed myoclonic contractions which spread to the hind leg of the same side until the cat fell in a torsion seizure, curving and twisting to the left. Then the convulsion became general and symmetrical, involving also the jaw, ears and facial muscles. The pupils were widely dilated. The seizure lasted 2 min each time, and in one cat a second seizure ensued upon handling the cat about 8 min after the injection. It was symmetrical and lasted also for about 2 mi. Isolated spells of myoclonic jerks persisted for several minutes after the end of the seizure. During the interval between the injection and the onset of seizure, the following changes in the behaviour of the cats took place. Immediately after the injection, the cats appeared to be frightened, cringed and growled when approached or patted. One cat ran into a corner in a crouching position, whereas the other remained fixed in the same place. The~ condition lasted until the fits occurred. After the fits there was a period of deep stupor. In one of the two cats, which is normally docile and quiet, the following features of 'catatonic stupor' described for the DFP cat were demonstrated. (a) When the cat was left undisturbed it showed only a few slow, spontaneous movements which were often stopped in an evidently uneasy posture. (b) While the cat was sitting a forepaw could be placed in an exaggerated extension on the floor and remained in this position when the hand was removed. (c) A foreleg could be twisted onto the cat's back without the use of constraint and be kept in this distorted position with barely a touch of the observer's finger for over a minute. (d) The cat could be brought into the 'upright standing' position by placing its front legs on the upper rung of an inverted stool. It remained in this posture for 90 sec or longer, after which time it merely lowered its front paws to the lower

8 INTRA VENTRICULAR ESERINE AND DFP rung, where it again remained for about half a minute. Similarly, its hind quarters could be suspended from the groin on the lower rung of an inverted stool and the cat remained for some time in this abnormal attitude. In any of these situations, when approached or blown at, it maintained its posture unaltered, but lashed its tail. An hour after the injection these features of catatonia were no longer present. The other cat, which was normally aggressive and easily angered, showed these qualities, after the state of stupor, and possibly confusion, following the fit, in an exaggerated way, hissing, putting its ears back and hitting out when a hand was brought near it. Otherwise it sat in its cage, completely inactive. DISCUSSION 495 Itching. The finding that eserine and DFP injected intraventricularly in relatively small doses regularly produce signs of itching or irritation which compel the cat to scratch itself, to wipe its face, lick and gnaw its paws, to shake its head and twitch its ears is of relevance to the phenomenon of itching in general. Naturally, it is not possible to state what compels the cat to act in a way in which man does when experiencing severe itching, and to state that the cat actually experiences this sensation. Nevertheless, we shall, in our inability ever to obtain this information in any way other than by analogy and inference, use the term 'itching'. This itching cannot be explained in any other way than by a central action of the anticholinesterases; we therefore have to distinguish between two possibilities in the causation of itching: itching originating in the skin and itching of central origin. The adequate physiological stimulus for itching originating in the skin may well be release of histamine in the superficial layers of the epidermis, as suggested by Schachter (1952) and Broadbent (1953). Signs of itching produced in animals by drug action on the central nervous system are not caused only by the anticholinesterases but have been described for a number of drugs injected intracisternally. The best known instance is morphine and its derivatives (Mehes, 1938), but according to Koenigstein (1948, 1951) the effect is produced by a variety of substances when administered intracisternally, amongst which eserine and potassium were outstanding; acetylcholine was also found by Koenigstein to be active in this way. Further, Kelen & McEachern (1949) observed that sodium fluoroacetate, on intracisternal injection, produced long-lasting 'scratching seizures' in cats. Koenigstein (1939) tried to localize the region from which morphine elicits a scratch response in cats, and concluded, by means of transection experiments, that the main site is the distal part of the floor of the fourth ventricle. In his experiments, the scratch response was used as the sole criterion of itching; the full syndrome we observed in our animals may well include an action of the anticholinesterases on the lining of the third ventricle also.

9 496 W. FELDBERG AND S. L. SHERWOOD A sensation of itching produced by the central action of the anticholinesterases could be brought about with or without the participation of the skin. Stimuli from the skin which normally do not produce such a sensation may do so when the periventricular grey matter is under the influence of a drug. This possibility was considered by Winiwarter (1939) in the case of morphine. He found that touching the skin after an intracisternal injection elicited bouts of scratching; on the other hand, acute deafferentation of the skin did not prevent spontaneous bouts of scratching. From these results he concluded that the skin is not essential for the itching produced by the morphine injection. So far no deafferentation experiments have been performed to analyse the mechanism of itching produced by the anticholinesterases, therefore no definite conclusion can be reached as to whether the effect is independent of afferent impulses in skin nerves or confined to central mechanisms. There are other less plausible ways in which the anticholinesterases could produce the sensation of itching by their central action. They could initiate efferent impulses to the skin via the sympathetic or the sensory fibres, stimulated antidromically, and by the effect of these impulses produce changes in the skin which then, in their turn, could evoke the sensation of itching. Or else the anticholinesterases, by their action on the ventricular lining, might produce changes in other parts of the body, either through hormone action or through nervous activity, and the sensation of itching might result from these alterations. It will not always be easy to assess whether the itching produced on systemic administration of a drug is a central or a peripheral effect, for a drug may produce itching when applied to the ventricular system and be a peripheral histamine liberator as well. Morphine, for instance, is a known histamine liberator and by this action produces itching in the skin, but it also causes the signs of itching on cisternal injection in doses which would not allow sufficient amounts to reach the general circulation for producing the effect in the skin. Therefore, the well-known pruritus in man after the administration of morphine may, in some cases, be of peripheral origin, in others of central, and again in others be a combination of both mechanisms. Similar considerations apply to the well-known pruritus seen in obstructive and hepatic jaundice. Schachter (1952) showed that bile salts release histamine from perfused skin preparations, and suggested that histamine liberation produces or contributes to the symptoms of pruritus in jaundice. It may well be that bile salts, like morphine, have a central pruritic effect as well, as other metabolites may have, such as in the case of diabetes or uraemia. There are a number of clinical observations of itching which are unlikely to be due to primary skin conditions, and where the itching may originate from the same site in the central nervous system as is affected by the anticholinesterases in our experiments. This applies to the itching of the nose in raised

10 INTRAVENTRICULAR ESERINE AND DFP 497 intracranial pressure and to the itching of lichen planus, since it is so dramatically relieved by lumbar puncture and removal of a few ml. of cerebrospinal fluid (Ravaut, 1927; Whitfield, 1928). Since itching is a characteristic sign of such different anticholinesterases as eserine and DFP, and has also been in part evoked by central application of acetylcholine, the probability is great that they both produce this effect by virtue of their cholinesterase inhibiting properties, and thus through accumulation of acetylcholine in the regions of the brain bordering the ventricular system. From this it would follow that the cells affected by the accumulated acetylcholine are impinged upon by cholinergic neurones. Motor phenomena. Apart from the motor effects associated with the sensation of itching or irritation, eserine as well as DFP caused changes in stance, gait, and posture and, in larger doses, DFP produced convulsions. Centrally induced motor phenomena have been described frequently for both anticholinesterases when injected arterially, intrathecally or intracisternally, or when applied locally to different parts of the central nervous system. Without further topographic electrical analysis it cannot be stated with certainty from which points in the brain the anticholinesterases, when given intraventricularly, produce the motor phenomena. They may well all originate from the diencephalon, because it is known, through the classical experiments of Hess, that electrical stimulation at various points in the neighbourhood of the third ventricle elicits a variety of complex patterned motor phenomena. This assumption is favoured by the finding that large doses of acetylcholine in the ventricles also lead to general convulsions, because it is difficult to see how acetylcholine in the absence of an anticholinesterase could penetrate deeply into the surrounding tissue, rich in cholinesterase, without being hydrolysed. We must therefore accept the view that acetylcholine can produce motor phenomena from some region close to the ventricular surface. If this is true for acetylcholine, it is likely to apply also to eserine and DFP. The motor phenomena produced by these anticholinesterases are thus thought to result from inhibition of cholinesterase and accumulation of acetylcholine in the diencephalon near the ventricular surface. Stupor and 'catatonia' appear to be characteristic features of the presence of acetylcholine or anticholinesterases in the ventricular system. The condition is first recognized by a general reduction of activity and culminates in a state in which the animal fails to extricate itself for many minutes from situations which must be uncomfortable and certainly are unnatural. Whilst the condition of reduced motor activity progresses, a change in awareness appears to take place. First, whilst the cat still maintains at least a proportion of its previous activity, it interrupts these activities for one or two seconds, evidently unaware, for the moment, of events in its surroundings. The condition resembles momentary 'absences' in man, which become gradually longer and more 32 PHYSIO. CXXV

11 498 W. FELDBERG AND S. L. SHERWOOD frequent. At the height of stupor the cat is nevertheless capable of moving, running and jumping when stimulated sufficiently, without any signs of motor disability. The condition is that of 'catatonia' observed in cats after lesions of the mid-brain (Bailey, 1948) and imitates in many details the reactions of catatonic patients. For instance, the finding that during this condition a limb can be placed and kept in abnormal postures without restraint resembles the feature of 'waxy flexibility' characteristic of catatonic stupor in man. Similarly, the observations that the cat when dropped into its cage retains the attitude in which it landed, or betrays some reactions to stimuli by lashing its tail or pricking its ears without, however, performing any other movements, recall behaviour patterns of catatonic patients. De Jong (1945) pointed out that in man catatonia is such a frequent occurrence in schizophrenia that the two terms are often used, although wrongly, synonymously. This raises the question of whether there are other attributes characteristic of schizophrenia to be found in response to anticholinesterases. It is interesting to recall in this connexion the early observation of Harnack & Witkowsky (1876) on subcutaneous injection of eserine into an epileptic idiot: apart from convulsions which occurred, the idiot behaved as if he had hallucinations. More recently Grob, Lilienthal, Harvey & Jones (1947) found that daily intramuscular administration of DFP led to insomnia, nightmares, mental confusion and hallucinations. These clinical observations have been confirmed by Rowntree, Nevin & Wilson (1950). In addition, they found that DFP produced in a number of schizophrenic patients 'an "activation" of the psychosis or the reappearance in chronic cases of the florid symptoms which had characterized the onset of the illness'; Some of the behavioural changes of our cats may also be due to something in the nature of hallucinations. At, times the animals showed by their head, ear and eye movements that they were alerted in response to stimuli, perhaps noises, which were not perceived by the observer. The unaccountable itching is perhaps also a tactile hallucination, and again it is interesting to note that some schizophrenic patients 'continuously scratch their faces' (Kraepelin, 1919). De Jong (1945) lists a number of drugs, of which bulbocapnine is the best known, which produce a condition of experimental catatonia in animals. We ourselves found that propylene glycol injected in small amounts intraventricularly produced as a late effect a condition in which the cat could be placed in abnormal postures and retained these for several minutes. The condition has a certain resemblance to the 'catatonic' stupor seen after DFP and eserine with which it can be confused. However, the condition is different. For instance the body sags when the animal is suspended in abnormal postures, the eyes remain shut or half shut, the cat is apathetic and sluggish, movements when present are extremely slow and the condition is best described as one of torpor and languor rather than of stupor. It is possible that some of the

12 INTRAVENTRICULAR ESERINE AND DFP 499 conditions described by de Jong as experimental catatonia resemble that seen after propylene glycol. We do not know why the effect of propylene glycol occurs so late after the injection. The fact, however, that when given in relatively small doses propylene glycol produces central effects on intraventricular injection, may serve as a warning to those observing central effects of DFP if the solutions used for injection are obtained, as is customary, from a stock solution made up in propylene glycol. The interest of the production by acetylcholine and the anticholinesterases of a condition of 'catatonic stupor' from the ventricular system lies in the fact that it indicates cholinergic neuronal activity or excess of acetylcholine, in the region of the periventricular grey matter, as the cause for this change in behaviour. It may well be that the hallucinatory phenomena seen in patients after DFP are also due to its cholinesterase-inhibiting effect in this diencephalic region. Similar considerations have led Sherwood (1952) to use cholinesterase in therapeutic trials on catatonic patients. He found that, given intraventricularly, preparations of true cholinesterase interrupted catatonic stupor in schizophrenic patients. SUMMARY 1. Injections were made of eserine, diisopropylfluorophosphonate (DFP) and large doses of acetylcholine into the right lateral cerebral ventricle of the unanaesthetized cat through a cannula permanently implanted in the skull. 2. Eserine and DFP: By the relative prominence of signs, three stages which overlap can be distinguished after ,ug eserine sulphate oi 100,ug DFP. During the first stage the cat has the appearance of severe itching and irritation, as evidenced by intense scratching, vigorous wiping with a foreleg over the face and head, and washing of the forelegs, often preceded by bouts of shaking the head and twitching the ears. In addition, there are peculiar jaw movements. The second stage is characterized by changes in stance, gait, and posture. There is increased tone in the limb muscles, quivering movements of the ears, head and shoulders, and tremor of the leg muscles. In addition, there are signs of respiratory embarrassment. The third stage consists of an alteration of awareness, including the development of stupor with signs of 'catatonia'. With larger doses of DFP (200,g) there is, in addition, an initial stage of agitation with signs of fear and anger, and seizure-like activity develops within the first hour after the injection. 3. Propylene glycol injected intraventricularly is not wholly ineffective but produces after a latency of min, a condition of torpor and languor which bears a certain resemblance to the third stage seen after eserine and DFP. 32-2

13 500 W. FELDBERG AND S. L. SHERWOOD 4. Acetylcholine. Large doses (1 mg) produce one or two convulsions which last for about 2 min, followed by deep stupor sometimes reaching the full picture of 'catatonia' for a short time. 5. In the discussion the view is advanced that the itching, the motor phenomena, and the 'catatonic' stupor produced by the anticholinesterases result from inhibition of cholinesterase and accumulation of acetylcholine in the region of the periventricular grey matter. The disorders produced in the cat in this way bear a close similarity to phenomena seen in schizophrenic patients. REFERENCES BAILEY, P. (1948). Alterations of behaviour produced in J. nerv. ment. Dis. 107, cats by lesions in the brain stem. BRENNER, C. & MERRITT, H. H. (1942). Effect of certain choline derivatives on electrical activity of the cortex. Arch. Neurol. P8ychiat., Chicago, 48, BROADBENT, J. L. (1953). Observations on itching produced by cowhage, and on the part played by histamine as a mediator of the itch sensation. Brit. J. Pharmacol. 8, FELDBERG, W. & SHERWOOD, S. L. (1953). A permanent cannula for intraventricular injections in cats. J. Physiol. 102, 3-4P. FELDBERG, W. & SHERWOOD, S. L. (1954). Injections of drugs into the lateral ventricle of the cat. J. Physiol. 123, GROB, D., LILIENTHTA, J. L. Jr., HARVEY, A. M. & JONEs, B. F. (1947). The administration of diisopropyl fluorophosphonate (DFP) to man. 1. Effect on cholinesterase and systemic effects. John8 Hopk. Ho8p. Bull. 81, HARNACK, E. & WITKOWSKI, L. (1876). Pharmakologische Untersuchungen iiber das Physostigmin und Calabarin. Arch. exp. Path. Pharmak. 5, DE JONG, H. H. (1945). Experimental Catatonia. Baltimore: The Williams and Wilkins Co. KELEN, A. & McEACHERN, D. (1949). Some effects of di-isopropyl fluorophosphate (DFP) and fluoroacetate on the central nervous system. Canad. J. Res. E, 27, KOENIGSTEIN, H. (1939). tber Localisationsversuche des durch Morphium ausgelosten 'Kratzwerkes' im Zentralnervensystem. Arch. int. Pharmacodyn. 62, KOENIGSTEIN, H. (1948). Experimental study of itch stimuli in animals. Arch. Derm. Syph., N. Y., 57, KoENIGSTEIN, H. (1951). Shifting of cations in the cerebrospinal fluid as a cause of pruritus. J. invest. Derm. 17, KRAEPELIN, E. (1919). Dementia Praecox and Paraphrenia, p. 43. Edinburgh: Livingstone. MEHES, J. (1938). Experimentelle Untersuchungen uber den Juckreflex am Tier. 2te Mitteilung. Auslosen heftiger Juckanfalle bei der Katze durch introcisternale Injektionen von Morphium und einige seiner Derivate. Arch. exp. Path. Pharmak. 188, RAVAUT, P. (1927). Lichen plan et ponction lombaire. Bull. Soc. franc Derm. Syph. 34, ROWNTREE, D. W., NEVIN, S. & WILSON, A. (1950). The effects of diisopropylfluorophosphonate in schizophrenia and manic depressive psychosis. J. Neurol. P8ychiat. 13, SCHACHTER, M. (1952). Release of histamine from skin by neoarsphenamine and bile salts. J. Physiol. 116, lop. SHERWOOD, S. L. (1952). Intraventricular medication in catatonic stupor. Brain, 75, WHITFIELD, A. (1928). The treatment of lichen planus. Lancet, 214, WINIWARTER, F. (1939). Ober die pharmakologische Analyse des Ohrkratzreflexes. Arch. int. Pharmacodyn. 62,