Descending influences from the lateral hypothalamus and amygdala coverge onto medullary taste neurons

摘要

The lateral hypothalamus (LH) and the central nucleus of the amygdala (CeA)exert an influence on many aspects of ingestive behavior.These nuclei receive projections from several areas carrying gustatory and viscerosensory information,and send axons to these nuclei as well,inlcuding the nucleus of the solitary tract (NST).Gustatory responses of NST neurons are modulated by stimulation of the LH and the CeA,and by several physiological factors related to ingestive behavior.W einvestigated the effect of both LH and CeA stimulation on the activity of 215 taste-responsive neurons in the hamster NST.More than half of these neurons (113/215) were modulated by electrical stimulation of the LH and/or CeA;of these,52 cells were inlfuenced by both areasoften bilaterally.The LH inlfuenced more neurons than the CeA (101 versus 64 cells).Contralateral stimulation of these forebrain areas was more often effective (144 responses) than ipsilateral (74).Modulatory effects were mostly excitatory (102 cells);11 cells were inhibited,moslty by ipsilateral LH stimulation.A subset of these cells (n=25) was examined for the effects of microinjection of DL-homocysteic acid (DLH),a glutamate receptor agonist,into the LH and/or CeA.The effects of electrical stimulation were completely mimicked by DLH,indicating that cell somata in and around the stimulating sites were responsible for these effects.other cells (n=25) were tested for the effects of electrical stimulation of the LH and/or CeA on the responses to taste stimulation of the tongue (32 mM sucrose,NaCl and quinine hydrochloride,and 3.2 mM citric acid).Responses to taste stimuli were enahnced by the excitatory inlfuence of the LH and/or CeA.These data demonstate that descending influences form the LH and CeA reach many of the same cells in the gustatory NST and canmodulate their responses to taste stimulation.