Cholinergic mechanisms in the neurocontrol of the branchial heart of the cephalopod Sepia officinalis L.

Cholinergic mechanisms controlling the branchial heart of the cephalopod Sepia officinalis L. were examined. In vitro tests indicate that acetylcholine (ACh) exerts a dose-dependent negative inotropic and chronotropic effect. Although the nicotinic agonists carbachol and nicotine mimic the effects of ACh closely, the muscarinic agonists pilocarpine, muscarine and oxotremorine induce only a slight inhibition of amplitude and frequency. Other agents tested (including atropine, pirencepine, hexamethonium, tetraethylammonium (TEA), d-tubocurarine and alpha-bungarotoxin) confirm that the acetylcholine receptor in branchial heart muscle is probably nicotinic.