Abstract
Our previous experiments using rats suggested that autonomic responses accompanying with nausea were controlled by neurons near the nucleus ambiguus (NA) of medulla oblongata, and these responses were produced via neurokinin 1 receptor (NK1R) activation. In this study, the changes of activities in the neurons near NA to tetanus stimulation and NK1 antagonist and/or agonist were investigated. Whole-cell recording was applied to the neurons near the NA in coronal slice preparations of brainstem isolated from infant rat (6-12 days). The frequency of spontaneous activities of neurons (n=18) was increased (39%) or decreased (28%) by perfusion of substance P (SP, 1μM), a selective agonist of NK1R. The changes of amplitude of excitatory postsynaptic currents (EPSCs) were recorded in the 29 neurons near NA. EPSCs evoked by electrical stimulation of adjacent area to the recording neuron were enhanced (28%) or inhibited (21%) by perfusion of SP. Furthermore, in the several neurons, tetanus stimulation (100Hz) induced the augmentation of amplitude of EPSCs and these augmentation were canceled by perfusion of NK1R antagonist, sendide (1μM).These results suggest that SP acts as neuromediator, which plastically changes the reactivity of neurons near NA via NK1R activation and hence might participate in generating autonomic responses accompanying with nausea. [J Physiol Sci. 2007;57 Suppl:S239]
