Convergence of gastric and hepatic information in brain stem neurons of the rat

Convergence of gastric and hepatic information in the nucleus of the solitary tract (NTS) was investigated by single-pulse electrical stimulation of the hepatic and the gastric branches of the vagus. Facilitation induced by both stimuli occurred most often in responses of neurons in the NTS, indicating convergence of information there. In a second experiment using gastric distension and portal infusion of glucose to analyze such convergence, activation by gastric distension and suppression by portal glucose was the most prominent combination of responses to both stimuli. This confirmed the results of electrical stimulation, because distension increases the firing rate of gastric afferents and glucose infusion decreases the firing rate of hepatic afferents. Analysis of the responses to varying degrees of gastric distension revealed that some NTS neurons are activated by weak distension, but inhibited by strong distensions.