Modulation of lateral hypothalamic single unit activity by gastric and intestinal distension

Single unit discharges in the lateral hypothalamic area (LH) were extracellularly recorded in chloralose anesthetized cats, while gastric or intestinal distension was performed. 47 out of 95 units were sensitive to gastric distension. Both phasic or tonic increases and decreases in firing rate were observed. Out of 41 units sensitive to gastric filling, 7 were also responsive to gastric emptying, exhibiting changes in the same direction to positive and negative variation in gastric pressure. Intestinal distension elicited changes in firing rate in 15 out of 34 units tested. As during gastric distension, units decreased or increased in firing rate while distension of the lumen was performed. The latencies of responses to gastric and intestinal distension were very short (less than one second) and were consistent with the functional properties of gastrointestinal mechanoreceptors previously described. In addition, 5 out of 25 units sensitive to gastric or intestinal distension, were responsive to both gastric and intestinal distensions exhibiting changes in the same direction. In this case, vagus nerve stimulation produced the same effect as the gastro-intestinal distensions. The results are discussed in terms of convergence of gastric and intestinal mechanoreceptor inputs on lateral hypothalamic neurons, in relation to the propagation of ingested food throughout the digestive tract.