The effect of intrahypothalamic administration of sodium pentobarbital on eating behaviour and feed intake in chickens

The effect of intrahypothalamic administration of sodium pentobarbital on eating behaviour and feed intake in chickens

Physiology and Behavior, Vol. 10, pp. 97-100, Brain Research Publications Inc., 1973. Printed in U.S.A. The Effect of Intrahypothalamic Administrati...

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Physiology and Behavior, Vol. 10, pp. 97-100,

Brain Research Publications Inc., 1973. Printed in U.S.A.

The Effect of Intrahypothalamic Administration of Sodium Pentobarbital on Eating Behaviour and Feed Intake in Chickens N. SNAPIR, B. ROBINZON, M. GODSCHALK, E. D. HELLER AND M. PEREK

Department o f Poult~ Science and Animal Hygiene, The Hebrew University of Jerusalem Faculty o f Agriculture, Rehovot, Israel

(Received 19 June 1972)

SNAPIR, N., B. ROBINZON, M. GODSCHALK, E. D. HELLER AND M. PEREK. The effect of intrahypothalamic administration of sodium pentobarbital on eating behaviour and food intake in chickens. PHYSIOL. BEHAV. 10(1) 97-100, 1973. -Injection of sodium pentobarbital solutions were carried out in chickens, through permanently implanted cannulas in the brain. Chickens with cannulas implanted in the third ventricle, above the hypothalamic ventrom~lial area, responded with immediate increase in feed intake and vigorous pecking behaviour which lasted from 10-60 rain. Chickens with cannulas implanted in the posterior lateral hypothalamus showed no changes in their feed intake or eating behaviour after sodium pentobarbital injection. The results with chickens correspond to those obtained with rats, eats and dogs. Sodium pentobarbital

Chickens

Feed intake

Eating behaviour

HYPERFHAGIA has been produced in many animals with appropriate lesions in the hypothalamus [3, 11 ]. Destroying of the hypothalamic ventromedial area in several avian species (chicken [8, 9, 121, Zonotrichia albicollis 17] and goose [1 ]) caused an increase in feed intake, lasting for various lengths of time. While it was shown that a temporary inactivation of the ventromedial area, functioning as a satiety center, by procaine or sodium pentobarbital in rats [4, 101, goats [2] and c a t s [51 resulted in immediate increase of feed intake, no such experiments have been reported with chickens. Generally, after placement of hypothalamic ventromedial electrolytic lesions inchickens, a period of 3 - 8 days passes until hyperphagia initiates (authors' unpublished data). Based on the assumption that a momentary hypothalamic regulation of feed intake exists in the chicken, it was worthwhile to examine, whether a temporary inactivation of the area bordered with the third ventricle, including the hypothalamic ventromedial area, would induce an immediate increase in feed intake. In addition, attention was given to the eating behaviour of the chickens after such treatment.

Hypothalamic ventromedial area

this experiment. The birds were kept in individual cages, fed and watered ad lib. They were subjected to 14 hr light daily.

Surgery Each cock was implanted with one double cannula constructed according to Grossman's design [6]. The birds were anesthesized by IV injection of 0.6 ml sodium pentobarbital (Sombital, 6%, diluted with 10% Ethanol, 20% Propylen Glycol and 70% bidistilled water, Rafa, Israel) and held in a stereotaxic instrument. In five birds the tip of the cannula was implanted above the hypothlamic ventromedial area, in the third ventricle, but not in the ventromedial area itself. This was performed, because it was found that after long periods post implantation a damage could be developed in the brain area surrounding the cannulas' tip. (Authors' unpublished data). Our procedural design was aimed at carrying out repeated experiments in the same birds and it seemed therefore of importance to keep the hypothalamic ventromedial area undamaged. In another five cocks, the cannula was implanted more posteriorly, 2 mm laterally to the midline, and about in the same horizontal plane as the hypothlamic ventromedial area.

METHOD

Animals Ten, 4 month old White Leghorn cocks were used for 97

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SNAPIR, ROBINZON, GODSCHALK, HELLER AND PEREK

Procedure Daily individual feed intake was recorded during a period of one month postoperation. This was continuously measuredduring the period in which the injections were performed. Using a 10 u l syringe (Hamilton), five tal of saline (0.9% NaCl) was injected during 3 0 - 4 0 sec through the implanted cannulas. Following injection the birds were returned to their cages and their behaviour observed. The feed intake during the period of observation was measured at 20 and 60 rain postinjection. On the following day at the same hour, the birds were injected with different concentrations of sodium pentobarbital, keeping a volume of 5,,1, by the same procedure as described above. They were observed for their behaviour as well as for the feed consumption. After choosing the appropriate concentration of the sodium pentobarbital (60 tag/talL the described alternate injections procedure was repeated with each individual cock seven times during an experimental period of 50 days, at intervals of 7 days from each other. The selection of the a.m. concentration of the sodium pentobarbital was done on the basis of observations, in which lower dosages than used caused no response in eating behaviour, while higher dosages resulted in immediate sleep. At the end of the experiment, the birds were killed by decapitation, their brains were immediately removed and fixed in 10% neutral buffered formalin. After embedding in gelatin, frozen frontal serial sections of 25 thickness each were prepared and stained with thionin. The sections were subjected to microscopical observation for localization of the cannulas' tip. For further verification of the location of the cannulas' tip, postmortem intracannula marker injection was performed prior to pooling out the cannulas. RESULTS AND DISCUSSION Figure

1 presents

schematical

drawings

of

frontal

sections of the chicken diencephalon, showing the exact location in the brain of those tips of cannulas implanted above the hypothalamic ventromedial area, and of those implanted in the posterior lateral area. Figure 2 shows individual representative results of feed intake, measured at 20 and 60 min postinjection of saline or sodium pentobarbital. These typical results were repeatedly obtained in each individual bird, irrespective of day of observation. As can be seen from this figure, all birds with lateral implanted cannula responded with no increase in feed consumption after sodium pentobarbital injection, as compared with their feed intake after being injected with saline serving as self control. All cocks (Nos. l, 2, 3, 8, 13) with cannula implanted in the third ventricle, above the ventromedial area, increased substantially their feed intake in response to the sodium pentobarbital injection as compared to the saline injections. This increase was most pronounced in the first 20 min postinjection. The following table summarizes the effect of the saline and sodium pentobarbital (S. P. B.) injections on the feed intake of the birds: All birds who showed an increase in feed intake in response to the sodium pentobarbital injections, started to eat within one min after returning to their cages. Before starting to eat, the birds made a circle movement in their cages, pecking their own feathers for a while and then pecked vigorously the feed in the troughs in front of them. Sometimes the pecking movements were so speedy that no real feed could be consumed by the birds. While continuing eating, it happened in some cases, that the birds stretched out in a typical position so that the neck and head still showed the vigorous pecking behaviour, even though they were dizzy or almost asleep. Generally, the sodium pentobarbital injected birds continued nonstop eating for 1 0 - 6 0 min. When trying to disturb the birds by knocking on the feed troughs they did not pay attention and continued to eat. The typical response to the sodium

TABLE l

SUMMARY OF THE EFFECT OF SALINE AND SODIUM PENTOBARBITALINJECTIONS

20 min postinj. S.P.B. 300 tag/5 ~1 Third vent. implanted cann. birds Lateral implanted cann. birds (1) (3) (i) (2)

60 min postinj.

Saline 5 tal

S.P.B. 300 tag/5 tal

Saline 5 tal

25.2+-3.3 (1)

9.0+ 1.7 (2)

32.0+-2.6 (5)

14,4+_2.2(6)

9.8+- 1.7 (3)

13.4+_1.0 (4)

16.4+- 1.7 (7)

17.8+3.3 (8)

x (2) p<0.05 x (4) N.S. x (3)p<0.05 x (4) N.S.

(n=5 observations; g of food]bird; means +- S.E.)

(5) (7) (5) (6)

x (6) p<0.05 x (8) N.S. x (7) p<0.05 x (8) N.S.

INTRAHYPOTHALAMIC INJECTION OF SOLIUM PENTOBARBITAL

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FIG. 2. Individual representative results of feed intake measured at 20 and 60 rain postintrahypothalamic injections of saline or sodium pentobarbital in chickens. : = effect of sodium pentobarbital injection; 5 t~l (60 ;tg//~l). e---* effect of saline injection; 5 t~l (0.9% NaCI). Birds Nos. 1, 2, 3, 8 and 13 had cannulas above the hypothalamic ventromedial area. Birds Nos. 4, 17, 18, 19 and 21 had cannulas in the posterior lateral hypothalamus. Note: The daily feed intake of the birds participated in this experiment ranged between 100 and 110 g.

FIG. 1. Schematical drawings of frontal sections of the chicken diencephalon (courtesy of Drs. S. Feldman, N. Snapir and S. Lepkovsky, unpublished data) showing location of the tips of the cannulas in the third ventricle above the hypothalamic ventromedial area (Birds Nos. l, 2, 3, 8 and 13) and in the posterior lateral hypothalamic area (Birds Nos. 4, 17, 18, 19 and 21). III = third ventricle; V = hypothalamic ventromedial area; M = dorsal and ventromedial mammilary nuclei; S = pituitary stalk.

pentobarbital injection lasted for m a x i m u m period o f one hr. Afterwards, the birds behaved c o m p l e t e l y normally, and a total of normal a m o u n t of feed was c o n s u m e d in that particular day. The birds with the lateral implanted cannula responded s o m e t i m e s td" the sodium p e n t o b a r b i t a l injection with ataxic condition, and appeared drowsy, but never ate m o r e as c o m p a r e d to their feed intake after saline injection.

The results obtained in this work with the domestic fowl agree with the previous observations reported by Epstein [4] and Mabel e t al. [10] in the rat, Baile [2] in the goat and Feldberg [5] in the cat. This suggests also that in the chicken, like in mammals, t h e h y p o t h a l a m i c ventromedial area is involved in m o m e n t a r y inhibitory control mechanism of feed intake. The fact that the increase in feed intake post sodium pentobarbital injection continued only for a short period w i t h o u t affecting the normal a m o u n t of feed intake during the same day or on following days, may substantiate our conclusions.

REFERENCES 1. Auffray, P. and J. C. Blum. Hyperphagie et st~atose h~patique chez l'Oie apr~s l~sion du noyau ventro-medial de l'hypothalamus. C. r. Acad. ScL Paris. 270: 2362-2365, 1970.

2. Baile, C. A. and J. Mayer. Hyperphagia in ruminants induced by a depressant. Science 151: 458-459, 1966.

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3. Brobeck, J. R. Mechanism of the development of obesity in animals with hypothalamic lesions. Physiol. Rev. 2 6 : 5 4 1 - 5 5 9 , 1946. 4. Epstein, A. N. Reciprocal changes in feeding behavior produced by intrahypothalamic chemical injections. Am. Z Physiol. 199: 9 6 9 - 9 7 4 , 1960. 5. Feldberg, W. Anaesthesia and sleep-like conditions produced by injections into cerebral ventricles of the cat. J. Physiol. {Lond.) 140: 2 0 - 2 1 , 1958. 6. Grossman, S. P. Direct adrenergic and cholinergic stimulation of hypothalamic mechanisms. Am. J. Physiol. 202: 872-882, 1962. 7. Kuenzel, W. J. and C. W. Helms. Hyperphagia, polydispia, and other effects of hypothalamic lesions in the white-throated sparrow, Zonotrichia albicollis. Condor 72: 6 6 - 7 5 , 1970,

SNAPIR, ROBINZON, GODSCHALK, HELLER AND PEREK

8. Lepkovsky, S. and M. Yasuda. Hypothalamic lesions, growth and body composition of male chickens. Poultry Sei. 45: 5 8 2 5 8 8 , 1966. 9. Lepkovsky, S., N. Snapir and F. Furuta. Temperature regulation and appetitive behavior in chickens with hypothalamic lesions. Physiol. Behav. 3 : 9 1 1 - 9 1 5 , 1968. 10. Mabel, J. A., C. A. Baile and J. Mayer. Hyperphagia induced by ventricular pressure and pentobarbitone in normal and hypotl3alamic obese rats. Lancet 2: 4 7 2 - 4 7 3 , 1966. 11. Mayer, J. Genetic, traumatic and environmental factors in the etiology of obesity. Physiol. Rev. 33: 4 7 2 - 5 0 8 , 1953. 12. Snapir, N., I. Nir, F. Furuta and S. Lepkovsky. Effect of administered testosterone propionate on cocks funcitonally castrated by hypothalamic lesions. Endocrinology 84: 611 -618, 1969.