Differential effect of nicotinic agonists on the [H-3]Norepinephrine release from rat hippocampal slices

The aim of this study was to investigate the mechanisms involved in the eff ect of nicotinic agonists on the [H-3]norepinephrine ([H-3]NE) release from rat hippocampal slices. The stimulatory effect of nicotine, cytisine, epib atidine and anatoxin-A was completely blocked by the nicotinic antagonist m ecamylamine (10 muM). In contrast, the effect of dimethylphenylpiperazinium (DMPP) was only partially inhibited by mecamylamine but was completely blo cked by the NE uptake inhibitor desipramine (DMI, 10 muM). Finally, the eff ect of lobeline was not affected by mecamylamine and was only partially blo cked by DMI. Our data indicate that the majority of nicotinic agonists incr ease the release of [H-3]NE exclusively via stimulation of nicotinic acetyl choline receptors (nAChRs). DMPP, in addition to the stimulation of nAChRs, also evokes a carrier-mediated release. Lobeline has no stimulatory effect on nAChRs, induces a carrier-mediated release and has a further action of unidentified mechanism. Our results suggest that special caution is require d for the interpretation of data, when DMPP or lobeline are used as nicotin ic agonists.