Nicotine-induced noradrenaline release from the isolated rat stomach by activation of L- and N-type calcium channels

We examined the effect of nicotine on the release of endogenous noradrenali ne (NA) from the isolated, vascularly perfused rat stomach. The stomach was perfused via the coeliac artery with Krebs-Ringer solution containing 10 m u M pargyline at a constant flow rate of 4 ml per minute. Nicotine was once applied in the perfusion medium for 2 min. Nicotine (10(-6)-10(-4) M) evok ed NA release in a concentration-dependent manner. The nicotine (3 x 10(-5) M)-evoked NA release was abolished by hexamethonium and tetrodotoxin. Dilt iazem and isradipine [blockers of L-type voltage-activated calcium channel (VACC)] and omega-conotoxin GVIA (a blocker of N-type VACC) also abolished this nicotine-evoked NA release. Previously we reported that N-type, but no t L-type, VACCs are located on the gastric postganglionic sympathetic nerve terminals, since the NA release evoked by electrical stimulation of periar terial nerves around the left gastric artery (postganglionic sympathetic ne rves) was abolished by w-conotoxin GVIA, but not by diltiazem (Yokotani et al., Jpn. J. Pharmacol. 78, 75 - 77, 1998). From these results, it was sugg ested that nicotine activates nicotinic acetylcholine receptors located on the sympathetic ganglia, thereby evoking NA release by activation of L-type VACC located on the gastric sympathetic ganglia and N-type VACC probably l ocated on the sympathetic nerve terminals in the rat stomach.