Transient responses of heart rate, arterial pressure, and head movement at the beginning of eating in awake cats.

Time courses of heart rate (HR), arterial pressure (AP), and head movement at the beginning of eating were analyzed in conscious cats. The cats were trained to eat when movements of their body trunks were restrained. Food was presented for 10 sec at intervals of 100 sec. With the abrupt presentation of food, a head-down movement occurred immediately and thereafter eating started with a mean latency of 1.6 sec. During eating HR increased by 22% from the preeating value and AP was elevated by 11%. To determine the time relation between the onset of eating and the change in each variable in response to eating, mean time courses of HR, AP, and head movement were obtained from 7-40 trials in each cat. The head-down movement preceded the onset of eating by 1.3 sec. The increase in HR preceded the onset of eating by 0.2 sec; the change in AP followed it by 3-4 sec. This indicated that the increase in HR was not induced reflexly either by food intake or by the change in AP. After administration of hexamethonium, the changes in HR and AP in response to eating were abolished, although eating was evoked by the food presentation. Additionally, the increase in HR was also reduced by propranolol and atropine. Thus, the acceleration of HR at the beginning of eating may be induced by central activation of the autonomic nervous system.