The rat nucleus paragigantocellularis as a relay station to mediate peripherally induced central effects of nicotine.

Previous electrophysiological studies have shown that intravenously administered nicotine in low doses indirectly excites noradrenergic locus coeruleus (LC) neurons. In the present study this effect of nicotine was attenuated (to about 25% of control response) by injection of lidocaine into the nucleus paragigantocellularis (PGi) whereas injection into the nucleus prepositus hypoglossi (PrH) had no effect in this regard. Whereas the basal firing rate of LC neurons was not affected by lidocaine injection into the PGi, more than 50% of the LC neurons displayed increased firing rate following lidocaine injection into the PrH. It is suggested that the peripherally induced effect of nicotine on LC neurons is indirectly mediated via activation of the PGi.