Lateral hypothalamic sites eliciting eating affect medullary taste neurons in rats.

A hypothetical functional relationship between the feeding area of the lateral hypothalamus and the medullary and pontine taste areas was assessed in rats. Multiple electrodes were implanted in the lateral hypothalamus and the animals which exhibited eating upon electrical stimulation were selected. Then under pentobarbital anesthesia, the hypothalamus was electrically stimulated while unit activity of medullary and pontine taste areas was recorded. Electrical stimulation of the hypothalamus at sites which elicited eating affected 22% of gustatory neurons, 13% of proprioceptive neurons sensitive to oropharyngeal stimuli but only 0.2% of the remaining nongustatory neurons. Electrical stimulation at nonfeeding sites affected 3% of the gustatory neurons. The electrical stimulation of the hypothalamus had the same inhibitory or excitatory effect on a given gustatory neuron as the sapid stimulation of the tongue did. These results are discussed in terms of the taste pathways and their possible role in electrically elicited feeding.