Effects of microelectrophoretically applied acetylcholine- and angiotensin-antagonists on the paraventricular neurosecretory cells excited by osmotic stimuli.

Extracellular action potentials were recorded from neurons identified antidromically as neurosecretory cells in the paraventricular nucleus of urethane-anesthetized rats. An intracarotid injection of 0.6 M NaCl increased the firing rate of 26 out of the 33 neurosecretory cells tested. The excitation induced by hypertonic NaCl was blocked by hexamethonium in 6 of 10 neurosecretory cells with nicotinic-cholinergic receptors, by atropine in 4 of 5 cells with muscarinic-cholinergic receptors and by [Sar1, Ala8]-angiotensin II in 5 of 12 cells with angiotensin II receptors. These results suggest that nicotinic- or muscarinic-cholinergic receptors and/or angiotensin II receptors appear to be involved in the final transmission of osmotic stimuli in the paraventricular neurosecretory cells.