Nicotine increases cytosolic Ca2+ in vasopressin neurons

Strong immunoreactivity for neuronal nicotinic acetylcholine receptor alpha 4 subunit was detected in neurons of the supraoptic nucleus (SON). At the ultrastructural level, immunoreactivity for alpha 4 was detected in the post-synaptic membranes as well as in the cytoplasmic matrices in the magnocellular neurons. Nicotine (1-10 mu M) increased cytosolic Ca2+ concentrations ([Ca2+](i)) in isolated arginine-vasopressin (AVP)-containing neurons in the rat SON. Nicotine (10 mu M) was less potent in increasing [Ca2+](i) in AVP-containing neurons than noradrenaline (1 mu M), a known neurotransmitter in the SON. The nicotine-induced [Ca2+](i) increase in AVP-containing neurons was markedly reduced when pre-treated with a protein kinase A (PKA) blocker, H89 (40 mu M). These findings suggest that nicotine, a known neurotransmitter in the SON, activates AVP-containing neurons via nicotinic acetylcholine receptor which is linked to stimulation of cAMP-PKA-regulated Ca2+ signaling pathway. (C) 1997 Elsevier Science Ireland Ltd.