Studies on the neural control of feeding in rat

Baillie, Peter (1961) Studies on the neural control of feeding in rat. PhD thesis, University of Glasgow.

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Two centres in the hypothalamus are known to exert control over feeding. Bilateral destruction of the ventromedial centres causes an increased intake of food i.e. hyperphagia, and bilateral destruction of the lateral centres results in no food being eaten i.e. aphagia. At present there is only speculation as to the way in which these neural lesions act. An investigation was undertaken to detect the changes in feeding behaviour which result from lateral lesions being made in the hypothalamus of the rat. Records of feeding behaviour were obtained from a Skinner box system in which rats were motivated by hunger to press a lever. As a result, food was made available to them and the relationship between the total number of lever-presses and the caloric intake in each 24 hour period was derived. Prom these results it was seen that the mean feeding patterns of rats was constant from day to day. After anaesthesia, there was a 40% decrease in both calorie intake and lever-pressing activity. There was a 50% decrease in calorie intake and lever-pressing following a sham operation in which no brain lesion was made. Bilateral lesions in the lateral hypothalamus resulted in complete aphagia for at least three days. During the same period, lever-pressing activity was minimal. This result suggests that the urge to eat was non-existent at that period. During recovery from the lesion operation lever-pressing activity increased significantly in every case, and was presumably due to recovery of the urge to eat. Calorie intake was zero for the first day on which lever-pressing was resumed in each experiment. Thereafter there was a recovery of feeding in some cases while other rats remained aphagic. Lever-pressing was continued throughout that recovery period. Histological examination of the brains of these rats showed that bilateral destruction of a similar area had been achieved in every case. Rats with gastric fistulae implanted were maintained for long periods and trained to feed by autoinjection of diet through the fistula. Intragastric feeding was as efficient as oral feeding in inhibiting gastric "hunger" contractions in rats with fistulae. Sequences of grooming behaviour also followed intragastric feeding but were not seen after lateral lesions were made in the hypothalamus. Intragastric feeding behaviour did not change after rats with fistulae were made aphagic by lateral hypothalamic lesions. Although unable to ingest food orally those rats maintained their intake of food by the direct intragastric route. The implications of those results suggest that the aphagia produced by lateral lesions of the hypothalamus is not primarily due to lack of the desire to eat. Recovery of lever-pressing activity during aphagia suggests that the urge to eat is still present although rats cannot ingest food orally. Rats with gastric fistulae are therefore able to feed by by-passing the oral mechanisms# Further observations suggest that the neural block caused by lateral lesions affects the act of swallowing, rather than the act of mastication. No damage to any discrete nerve pathway could be detected.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Neurosciences
Date of Award: 1961
Depositing User: Enlighten Team
Unique ID: glathesis:1961-73490
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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