Responses to repetitive afferent activity of rat solitary complex neurons isolated in brainstem slices.

The response of postsynaptic solitary complex neurons to repetitive stimulation (20-50 Hz) of the tractus solitarius were investigated by intracellular recordings in a brainstem slice preparation. Short duration stimuli (0.5 s) elicited increases in synaptic activity and short-term potentiation of synaptic potentials, both of which lasted approximately 1 min, plus a 10 s repolarization suppressed in the presence of glutamate ionotropic receptors antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10 microM) and 2-D-amino-7-phosphonoheptanoic acid (AP7, 50 microM). Longer (5 s) stimuli elicited 2-10 min depolarizations accompanied by membrane resistance increases and unaffected by glutamate ionotropic receptors antagonists. Our study reveals several mechanisms by which rhythmic visceral afferents may exert a tonic control of postsynaptic solitary complex neurons.