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Ethanol drinking elicited during electrical stimulation of the lateral hypothalamus
Physiology and Behavior. Vol. 7, pp. 793-795. Pergamon Press, 1971. Printed In Great Brttam
BRIEF COMMUNICATION Ethanol Drinking Elicited During Electrical Stimulation of the Lateral Hypothalamus' M. J. W A Y N E R A N D I. G R E E N B E R G
Brain Research Laboratory, Syracuse University, Syracuse, N. Y. 13210, U.S.A. AND R. J. C A R E Y A N D D. N O L L E Y
Syracuse Veterans Administration Hospital, Syracuse, N.Y. 13210, U.S.A. (Received 1 July 1971) WAYNER, M. J., 1. GREENBERG,R. J. CAREYAND D. NOLLEY. Ethanoldrinking elicited during electrical stimulation of the lateral hypothalamus. Prr~IoL. BErIAV.7 (5) 793-795, 1971.raThe fact that rats will drink intoxicating amounts of aver-
sire ethyl alcohol solutions during electrical stimulation of the lateral hypothalamus in a standard test chamber was demonstrated. The ingestion of ethanol was produced rapidly and daily for as long as 25 days without any obvious deleterious effects. Possible applications to the development of an animal model for the study of alcoholism are discussed. Lateral hypothalamus behavior
Ethyl alcohol
Alcoholism
Stimulus-bound behavior
Tim FACT THAT elicitation of many different behavior patterns by complex environmental stimuli is facilitated during various modes of lateral hypothalamic (LH) stimulation is well established [8, 10]. With increasing periods of stimulation, responses become stereotyped and the LH stimulation begins to exert a powerful influence in controlling the occurrence of the behavior. Although the behavior becomes stereotyped, relatively complex patterns of responses will emerge during LH stimulation. For example, a reliable so-called stimulus-bound eater accustomed to dry laboratory chow will during L H stimulation pick up and skillfully shell and ingest sunflower seeds. In the case of drinking, even aversive quinine solutions will be ingested by stimulus-bound drinkers during L H electrical stimulation [11]. In general ethanol solutions are also aversive to rats and other animals and for this reason it has been almost impossible to develop an adequate animal model for the study of alcoholism. Unusually large ethanol intakes occur during cerebral intraventricular infusion of ethyl alcohol [7] and schedule-induced polydipsia [6] and in the alcohol deprivation effect (ADE) [5] and sometimes during stress. All of these methods are limited by a variety of disadvantages: the maintenance of patent cannulas with intracerebral infusion, the reduction of body weight required for schedule-induced polydipsia, the short duration of A D E and the multiple problems of stress in-
Drinking
Ingestive
duction. Recently, electrical stimulation of the hypothalamus has been employed to induce the drinking of aversive ethanol solutions in relatively large quantities [1, 2, 9]. In addition it has been reported that electrical stimulation of the hypothalamus alone permanently alters the preference-aversion function for ethanol [3]. The purpose of the present repoct is to demonstrate that unusually large and inebriating amounts of aversive ethanol solutions will be ingested by rats during LH electrical stimulation. METHOD
Four rats with bilateral L H implanted bipolar electrodes were selected. Each animal was a confirmed drinker during LH electrical stimulation through at least one pair of electrodes in a standard test cage. The equipment and exact test procedures have been described previously [l 1]. The LH was stimulated with a 60 Hz constant current sine wave. Stimulation consisted of 30 trials of 60 see on and 30 see off for a total test session time of 45 rain. Current intensity was adjusted to that level which consistently produced water drinking. The same intensity was employed to induce drinking of ethanol in the test cage. Animals were stimulated in a 40 × 25 × 25 crn plastic box w i t h a stainless steel grid floor. Fluid intake in the test chamber was measured by
*The research was supported by NSF Grant GB-18414X and NIMH Grants 15473 and 16640. 793
794
WAYNER, GREENBERG, CAREY AND NOLLEY
means of a eudiometer tube fitted with a ball point stainless steel drinking tube flush with the plastic wall and 4.5 cm above the grid floor. Ethanol solutions were mixed from 95 per cent ethyl alcohol and distilled water. Animals were studied daily during the course of the experiment under two different sets of conditions. Two animals, A and B, one hooded rat from our own colony and one Sprague-Dawley albino, each weighing 400 g, were studied for three consecutive periods of 15 days. During each period the animals were given only 5, 10, or 20 per cent ethanol in the test cage. Only one solution was presented in the test cage for the 15 day period. In the home cage animals always had four choices of 5 per cent ethanol, 20 per cent ethanol, tap water and an empty tube. Positions o f each bottle were changed daily in a non-systematic order. Flinchjump determinations [4] were carried out on Rat A before testing began, before and after the last test trial, and 24 and 48 hr following the last test trial. Two additional SpragueDawley albinos, C and D, at 600 g and 450 g in body weight at the beginning of the experiment, were studied for a 25 day period during which only 20 per cent ethanol was available in the test cage. Both these animals had 5 per cent ethanol, 20 per cent ethanol, tap water and an empty tube present in their home cages at all times. Two concentrations of ethanol, 5 and 20 per cent, were presented in the home cage because 5 per cent falls within the narrow range of relatively weak ethanol solutions preferred by our strains of rats and 20 per cent is usually not ingested in significant amounts by our animals during moderately long periods of testing. RESULTS
All four animals ingested inebriating amounts of 20 per cent ethanol during daily test sessions of L H stimulation. During each test session animals became overtly intoxicated with obvious ataxia, disorientation and hypo-reactivity to startle stimuli. The current intensities required to elicit both flinch and jump in rat A were significantly elevated by the ethanol ingested during the test session. Although the animals became inebriated during the test session, drinking continued tO occur during L H stimulation. The mean volume of 20 per cent ethanol consumed by animals A and B during the 15 test periods was 5.4 and 4.4 ml or 2.1 and 1.8 g of ethyl alcohol per kg of body weight per day. During the 25 test sessions in which rats C and D were tested, they drank 6.1 and 4.8 ml or 1.6 and 1.8 g/kg. In our animals on ad lib food and water, approximately 1.5 g of ethyl alcohol per kg of body weight administered by stomach tube is an intoxicating dose. Also, animals A and B became inebriated when they drank 5 or 10 per cent ethanol during the test session. Rat A which preferred 5 per cent ethanol to tap water in the home cage also drank more 5 per cent ethanol
than tap water during the test session. Rat A drank a mean of 16.0 ml of 5 per cent ethanol and 12.5 ml of tap water during LH stimulation. Rat B which also preferred 5 per cent ethanol to tap water in the home cage drank 16.1 ml of 5 per cent ethanol and 16.0 ml of tap water during the LH stimulation test sessions. The animals in this study did not become addicted as there was no significant change in their home cage ingestion of 5 and 20 per cent ethanol during the course of the experiment. There was no evidence in terms of general observation and handling of withdrawal symptoms when the ethanol was removed. In rat A there was no obvious change in the flinch-jump threshold 24 and 48 hr after testing was terminated even though the ingestion of an inebriating amount during a test session definitely elevated the jump threshold as determined immediately after the session terminated while the animal was still intoxicated. Daily food intakes and body weights did not change significantly during the course of the experiment. Although animals ingested intoxicating amounts of ethanol in a single dose per day for as long as 25 days, these additional calories were not sufficient to depress daily food intakes. As blood alcohol and acetaldehyde levels were not determined, the actual amounts of ethanol metabolized were not estimated.
DISCUSSION
Results demonstrate unequivocally that inebriating amounts of aversive ethanol solutions will be ingested reliably in a short period of time by rats during LH electrical stimulation. Actually it is possible to administer predetermined amounts of alcohol and other fluids very precisely under these conditions. In addition, the problem of reduced food intake which usually accompanies daily ingestion of larger quantities of ethanol, because the animal tends to regulate its caloric intake, can be avoided by utilizing preparations in which one pair of L H electrodes produce drinking and the other pair on the opposite side of the hypothalamus produce eating. Consequently, it is possible to control and regulate both fluid and solid food ingestion very precisely. Thus, electrical stimulation of the LH is a very useful experimental method with many poSSible applications and significant advantages over several techniques now in use. It seems appropriate to mention in this context that one of our experimental rats from another study became ill and ceased eating and drinking for four days and lost 122 g in body weight. At the brink of complete inanition and possibly death, electrical stimulation of the L H was initiated and produced drinking of a nutritive fluid in the test cage. The animal began to gain in weight and after three days resumed spontaneous eating and drinking.
REFERENCES
1. Amit, Z. and M. H. Stem. P r e f ~ for alcohol in the laboratory rat. E.P.A. Meetings. Atlantic City, April 2--4. 1970. 2. Amit, Z., M. H. Stern and R. A. Wise. Alcohol preference in the laboratory rat induced by hypothalamic stimulation. ,Psyehopharmacologia, 17: 367-377, 1970. 3. Amit, Z. A further investigation of alcohol addiction in the laboratory rat induced by hypothalamic stimulation. E.P.A. Meetings. N.Y.C., April 15-17, 1971.
4. Evans, W. O. A new technique for the investigation o f some analgesic drugs on a reflexive behavior in the rat. Psychopharmacologia, 2: 318-325, 1961. 5. Le Magnen, J. t~tude de quelques facteurs associ~s ~ des modifications de la eonsommation spontan~ d'alcoh0i 6thyiique par le rat. J. PhysioL, Palls. 52: 873-884, 1960. 6. Lester, D. Self-maintenance of intoxication in the rat: Q. Jl. Stud. Alcohol, 22: 223-231, 1961.
ETHANOL DRINKING AND THE LATERAL HYPOTHALAMUS 7. Myers, R. D. Modification of drinking patterns by chronic intracranial chemical infusion. In: Thirst in the Regulation of Body Water, edited by M. J. Wayner. O~ford. Pergamon Press. 1964, p. 533-549. 8. Valenstein, E. S., V. C. Cox and J. W. Kakolewski. The hypothalamus and motivated behavior. In: Reinforcement and Behavior, edited by J. T. Tapp. N.Y. Academic Press, 1969, pp. 242-283. 9. Wayner, M. J. Effects of ethyl alcohol on lateral hypothalamic neurons. Symposium on Recent Advances in Studies of
795
Alcoholism. National Center for Prevention and Control of Alcoholism, NIMH. Wash. D.C. June 25-27, 1970. 10. Wayner, M. J. Motor control functions of the lateral hypothalamus and adjunctive behavior. Physiol. Behav. 5: 13191325, 1970. 11. White, S. D., M. J. Wayner and A. Cott. Effects of intensity, water deprivation, prior water ingestion and palatability on drinking evoked by lateral hypothalamic electric stimulation. Physiol. Behav. 5:611-619, 1970.
BRIEF COMMUNICATION Ethanol Drinking Elicited During Electrical Stimulation of the Lateral Hypothalamus' M. J. W A Y N E R A N D I. G R E E N B E R G
Brain Research Laboratory, Syracuse University, Syracuse, N. Y. 13210, U.S.A. AND R. J. C A R E Y A N D D. N O L L E Y
Syracuse Veterans Administration Hospital, Syracuse, N.Y. 13210, U.S.A. (Received 1 July 1971) WAYNER, M. J., 1. GREENBERG,R. J. CAREYAND D. NOLLEY. Ethanoldrinking elicited during electrical stimulation of the lateral hypothalamus. Prr~IoL. BErIAV.7 (5) 793-795, 1971.raThe fact that rats will drink intoxicating amounts of aver-
sire ethyl alcohol solutions during electrical stimulation of the lateral hypothalamus in a standard test chamber was demonstrated. The ingestion of ethanol was produced rapidly and daily for as long as 25 days without any obvious deleterious effects. Possible applications to the development of an animal model for the study of alcoholism are discussed. Lateral hypothalamus behavior
Ethyl alcohol
Alcoholism
Stimulus-bound behavior
Tim FACT THAT elicitation of many different behavior patterns by complex environmental stimuli is facilitated during various modes of lateral hypothalamic (LH) stimulation is well established [8, 10]. With increasing periods of stimulation, responses become stereotyped and the LH stimulation begins to exert a powerful influence in controlling the occurrence of the behavior. Although the behavior becomes stereotyped, relatively complex patterns of responses will emerge during LH stimulation. For example, a reliable so-called stimulus-bound eater accustomed to dry laboratory chow will during L H stimulation pick up and skillfully shell and ingest sunflower seeds. In the case of drinking, even aversive quinine solutions will be ingested by stimulus-bound drinkers during L H electrical stimulation [11]. In general ethanol solutions are also aversive to rats and other animals and for this reason it has been almost impossible to develop an adequate animal model for the study of alcoholism. Unusually large ethanol intakes occur during cerebral intraventricular infusion of ethyl alcohol [7] and schedule-induced polydipsia [6] and in the alcohol deprivation effect (ADE) [5] and sometimes during stress. All of these methods are limited by a variety of disadvantages: the maintenance of patent cannulas with intracerebral infusion, the reduction of body weight required for schedule-induced polydipsia, the short duration of A D E and the multiple problems of stress in-
Drinking
Ingestive
duction. Recently, electrical stimulation of the hypothalamus has been employed to induce the drinking of aversive ethanol solutions in relatively large quantities [1, 2, 9]. In addition it has been reported that electrical stimulation of the hypothalamus alone permanently alters the preference-aversion function for ethanol [3]. The purpose of the present repoct is to demonstrate that unusually large and inebriating amounts of aversive ethanol solutions will be ingested by rats during LH electrical stimulation. METHOD
Four rats with bilateral L H implanted bipolar electrodes were selected. Each animal was a confirmed drinker during LH electrical stimulation through at least one pair of electrodes in a standard test cage. The equipment and exact test procedures have been described previously [l 1]. The LH was stimulated with a 60 Hz constant current sine wave. Stimulation consisted of 30 trials of 60 see on and 30 see off for a total test session time of 45 rain. Current intensity was adjusted to that level which consistently produced water drinking. The same intensity was employed to induce drinking of ethanol in the test cage. Animals were stimulated in a 40 × 25 × 25 crn plastic box w i t h a stainless steel grid floor. Fluid intake in the test chamber was measured by
*The research was supported by NSF Grant GB-18414X and NIMH Grants 15473 and 16640. 793
794
WAYNER, GREENBERG, CAREY AND NOLLEY
means of a eudiometer tube fitted with a ball point stainless steel drinking tube flush with the plastic wall and 4.5 cm above the grid floor. Ethanol solutions were mixed from 95 per cent ethyl alcohol and distilled water. Animals were studied daily during the course of the experiment under two different sets of conditions. Two animals, A and B, one hooded rat from our own colony and one Sprague-Dawley albino, each weighing 400 g, were studied for three consecutive periods of 15 days. During each period the animals were given only 5, 10, or 20 per cent ethanol in the test cage. Only one solution was presented in the test cage for the 15 day period. In the home cage animals always had four choices of 5 per cent ethanol, 20 per cent ethanol, tap water and an empty tube. Positions o f each bottle were changed daily in a non-systematic order. Flinchjump determinations [4] were carried out on Rat A before testing began, before and after the last test trial, and 24 and 48 hr following the last test trial. Two additional SpragueDawley albinos, C and D, at 600 g and 450 g in body weight at the beginning of the experiment, were studied for a 25 day period during which only 20 per cent ethanol was available in the test cage. Both these animals had 5 per cent ethanol, 20 per cent ethanol, tap water and an empty tube present in their home cages at all times. Two concentrations of ethanol, 5 and 20 per cent, were presented in the home cage because 5 per cent falls within the narrow range of relatively weak ethanol solutions preferred by our strains of rats and 20 per cent is usually not ingested in significant amounts by our animals during moderately long periods of testing. RESULTS
All four animals ingested inebriating amounts of 20 per cent ethanol during daily test sessions of L H stimulation. During each test session animals became overtly intoxicated with obvious ataxia, disorientation and hypo-reactivity to startle stimuli. The current intensities required to elicit both flinch and jump in rat A were significantly elevated by the ethanol ingested during the test session. Although the animals became inebriated during the test session, drinking continued tO occur during L H stimulation. The mean volume of 20 per cent ethanol consumed by animals A and B during the 15 test periods was 5.4 and 4.4 ml or 2.1 and 1.8 g of ethyl alcohol per kg of body weight per day. During the 25 test sessions in which rats C and D were tested, they drank 6.1 and 4.8 ml or 1.6 and 1.8 g/kg. In our animals on ad lib food and water, approximately 1.5 g of ethyl alcohol per kg of body weight administered by stomach tube is an intoxicating dose. Also, animals A and B became inebriated when they drank 5 or 10 per cent ethanol during the test session. Rat A which preferred 5 per cent ethanol to tap water in the home cage also drank more 5 per cent ethanol
than tap water during the test session. Rat A drank a mean of 16.0 ml of 5 per cent ethanol and 12.5 ml of tap water during LH stimulation. Rat B which also preferred 5 per cent ethanol to tap water in the home cage drank 16.1 ml of 5 per cent ethanol and 16.0 ml of tap water during the LH stimulation test sessions. The animals in this study did not become addicted as there was no significant change in their home cage ingestion of 5 and 20 per cent ethanol during the course of the experiment. There was no evidence in terms of general observation and handling of withdrawal symptoms when the ethanol was removed. In rat A there was no obvious change in the flinch-jump threshold 24 and 48 hr after testing was terminated even though the ingestion of an inebriating amount during a test session definitely elevated the jump threshold as determined immediately after the session terminated while the animal was still intoxicated. Daily food intakes and body weights did not change significantly during the course of the experiment. Although animals ingested intoxicating amounts of ethanol in a single dose per day for as long as 25 days, these additional calories were not sufficient to depress daily food intakes. As blood alcohol and acetaldehyde levels were not determined, the actual amounts of ethanol metabolized were not estimated.
DISCUSSION
Results demonstrate unequivocally that inebriating amounts of aversive ethanol solutions will be ingested reliably in a short period of time by rats during LH electrical stimulation. Actually it is possible to administer predetermined amounts of alcohol and other fluids very precisely under these conditions. In addition, the problem of reduced food intake which usually accompanies daily ingestion of larger quantities of ethanol, because the animal tends to regulate its caloric intake, can be avoided by utilizing preparations in which one pair of L H electrodes produce drinking and the other pair on the opposite side of the hypothalamus produce eating. Consequently, it is possible to control and regulate both fluid and solid food ingestion very precisely. Thus, electrical stimulation of the LH is a very useful experimental method with many poSSible applications and significant advantages over several techniques now in use. It seems appropriate to mention in this context that one of our experimental rats from another study became ill and ceased eating and drinking for four days and lost 122 g in body weight. At the brink of complete inanition and possibly death, electrical stimulation of the L H was initiated and produced drinking of a nutritive fluid in the test cage. The animal began to gain in weight and after three days resumed spontaneous eating and drinking.
REFERENCES
1. Amit, Z. and M. H. Stem. P r e f ~ for alcohol in the laboratory rat. E.P.A. Meetings. Atlantic City, April 2--4. 1970. 2. Amit, Z., M. H. Stern and R. A. Wise. Alcohol preference in the laboratory rat induced by hypothalamic stimulation. ,Psyehopharmacologia, 17: 367-377, 1970. 3. Amit, Z. A further investigation of alcohol addiction in the laboratory rat induced by hypothalamic stimulation. E.P.A. Meetings. N.Y.C., April 15-17, 1971.
4. Evans, W. O. A new technique for the investigation o f some analgesic drugs on a reflexive behavior in the rat. Psychopharmacologia, 2: 318-325, 1961. 5. Le Magnen, J. t~tude de quelques facteurs associ~s ~ des modifications de la eonsommation spontan~ d'alcoh0i 6thyiique par le rat. J. PhysioL, Palls. 52: 873-884, 1960. 6. Lester, D. Self-maintenance of intoxication in the rat: Q. Jl. Stud. Alcohol, 22: 223-231, 1961.
ETHANOL DRINKING AND THE LATERAL HYPOTHALAMUS 7. Myers, R. D. Modification of drinking patterns by chronic intracranial chemical infusion. In: Thirst in the Regulation of Body Water, edited by M. J. Wayner. O~ford. Pergamon Press. 1964, p. 533-549. 8. Valenstein, E. S., V. C. Cox and J. W. Kakolewski. The hypothalamus and motivated behavior. In: Reinforcement and Behavior, edited by J. T. Tapp. N.Y. Academic Press, 1969, pp. 242-283. 9. Wayner, M. J. Effects of ethyl alcohol on lateral hypothalamic neurons. Symposium on Recent Advances in Studies of
795
Alcoholism. National Center for Prevention and Control of Alcoholism, NIMH. Wash. D.C. June 25-27, 1970. 10. Wayner, M. J. Motor control functions of the lateral hypothalamus and adjunctive behavior. Physiol. Behav. 5: 13191325, 1970. 11. White, S. D., M. J. Wayner and A. Cott. Effects of intensity, water deprivation, prior water ingestion and palatability on drinking evoked by lateral hypothalamic electric stimulation. Physiol. Behav. 5:611-619, 1970.