Lateral hypothalamic responses to pre-absorptive and post-absorptive signals related to amino acid ingestion.

This paper reports an investigation of the comparative effects of pre-absorptive and post-absorptive stimuli associated with amino acid ingestion on cat and rat lateral hypothalamic neuronal activity. Pre-absorptive signals, conveyed by the vagus nerve and originating from the small intestine while the amino acids are about to be absorbed, have been previously identified electrophysiologically in our laboratory [3]. They were found to selectively modulate the neuronal activity of some lateral hypothalamic (LHA) cells [4]. The effects of both pre-absorptive and post-absorptive signals associated with amino acid ingestion were analyzed with regard to their degree of convergence at the lateral hypothalamic level. The pre-absorptive signals consisted of either chemospecific information arising from intestinal chemoreceptors and related to the chemical nature of the ingested nutrient, or mechanical information arising from intestinal mechanoreceptors and related to distension. The post-absorptive signal consisted of a microiontophoretic application of amino acids known to selectively affect the neuronal activity of LHA amino acid-sensitive cells [15]. The convergence on these cells of the intestinal afferent amino acid-sensitive units was postulated in this study.