PERIPHERAL NICOTINE ADMINISTRATION INCREASES RUBRAL FIRING RATES IN THE URETHANE-ANESTHETIZED RAT

The presence of cholinergic input to the red nucleus (RN) in the cat i s demonstrated by choline acetyltransferase (ChAT) staining; however, it is unclear what effect this cholinergic input has on neurons of the RN. Further, the presence of cholinergic neurons in the rat RN has be en the subject of controversy. The present study examined the effects of intravenous injections of S(-)-nicotine tartrate (62.5-250 mu g/kg) on the firing rate of rubral neurons. Dose-dependent increases in fir ing rates were observed which were blocked by pre-treatment with the n icotinic antagonist, mecamylamine hydrochloride. Smaller consistent in creases were found after pretreatment with 62.5 mu g/kg or 125 mu g/kg doses of nicotine than were observed following the initial administra tion, suggesting a desensitizing response typical of nicotinic recepto rs.