Activity of single neurones in the hypothalamic feeding centres: effect of gastric distension.

1. Unit activity from neurones of hypothalamic ;feeding' and ;satiety' centres, and from adjacent hypothalmic regions, was recorded by means of steel micro-electrodes inserted by a stereotaxic method, under Dial anaesthesia.2. The spike frequency of these neurones was observed during inflation of the stomach with intragastrically placed balloons, and during electrical stimulation of the gastric branches of the vagus. As control measures, distension of the peritoneal cavity and stimulation of a sensory nerve were also carried out. These tests were repeated after severing the gastric vagal branches.3. In fasted animals the frequency of spontaneous discharge was slower in the units of the satiety centre as compared with those of the feeding centre. The spike frequency of neurones in these two hypothalamic regions maintained an inverse relationship in all experimental situations.4. Distension of the stomach and stimulation of the gastric vagal branches increased the spike frequency of satiety neurones, decreased the spike frequency of feeding neurones, and did not produce any change in spike frequency of adjacent hypothalamic neurones. A few units in the lateral mammillary region also changed their spike frequency on gastric distension. These responses were abolished after severing the gastric nerves.5. The results suggest that distension of the stomach brings about satiation through vagal afferents activating the hypothalamic satiety mechanism.6. The role of this in the nervous regulation of food intake is discussed.