Effects of GABA on acutely isolated neurons from the gustatory zone of the rat nucleus of the solitary tract

Responses of acutely isolated neurons from the rostral nucleus of thesolitary tract (rNST) to GABA receptor agonists and antagonists wereinvestigated using whole-cell recording in current clamp mode. The isolatedneurons retain their morphology and can be divided into multipolar,elongate and ovoid cell types. Most rNST neurons (97%), including all threecell types, respond to GABA with membrane hyperpolarization and a reductionin input resistance. The GABA(A) receptor agonist muscimol reduces neuronalinput resistance in a concentration-dependent manner, whereas the GABA(B)receptor agonist baclofen had no effect on any of the neurons tested. TheGABA and muscimol reversal potentials were both found to be -75 mV Both theGABA competitive antagonist picrotoxin and the GABA(A) receptor antagonistbicuculline block the effect of GABA in a concentration-dependent manner.These results suggest that GABA activates all neurons in the rNST and thatinhibitory synaptic activity is important in brainstem processing ofgustatory and somatosensory information.