Abstract
We examined role of the feeding center on salivation during feeding of various foods, using normal and feeding center-destroyed rats. For this examination rats were placed on a food deprivation schedule and allowed access to various food for 3 hours per day for one week. The foods were pellets, power diet, and 3 types of mashed diet (power diet : water = 1:1.5, 1:1, and 1:0.5). After training, the animals were anesthetized and the duct of left submandibular gland was cannulated for recording salivation, and a pair of stainless electrodes was inserted into the masseter muscle for recording EMG activities. The feeding center (lateral hypothalamus) was destroyed by passing of DC current. After recovery from anesthesia, the recording experiment was performed and following results were obtained: 1) In normal rats, the average salivary flow rates for 3 min were in the order power diet > hard mashed diet > medium mashed diet > food pellet > soft mashed diet; 2) total EMG activities for 3 min were similar in various foods; 3) when the ipsilateral feeding center was destroyed, salivation during feeding of various foods decreased by about 80%; 4) destruction of the contralateral feeding center yielded about 40% decrease in salivary flow rates; 5) no changes were observed in total chewing cycles or total EMG activities for 3 min. These results suggest that descending effects from the feeding center are essential for salivation during chewing, and involved in main neural network to evoke the masticatory-salivary reflex. [J Physiol Sci. 2007;57 Suppl:S236]
