6533b860fe1ef96bd12c3147

RESEARCH PRODUCT

Nicotinic drugs and postganglionic sympathetic transmission

subject

description

1. Isolated rabbit hearts with the sympathetic nerves attached were perfused with Tyrode solution. The noradrenaline output into the perfusate was measured fluorimetrioally. 2. When the niootinic autoinhibition produced by infusions of nicotine, DMPP, or acetylcholine (in the presence of atropine) was fully developed, the output of noradrenaline evoked by electrical stimulation of the postganglionic sympathetic nerves was not depressed. 3. Acetylcholine in the presence of atropine produced a transitory facilitation of the noradrenaline output evoked by sympathetic nerve stimulation. 4. Prolonged infusion of DMPP caused an adrenergic neurone block which was not observed after nicotine, or acetylcholine (plus atropine). The neurone block was clearly distinguished from the quickly developing autoinhibition produced by DMPP. 5. It is concluded that postganglionic sympathetic transmission does not involve excitation of nicotine receptors. The nicotinic block (autoinhibition) resembles the “non-depolarizing block” observed on autonomic ganglion cells and may be attributed to occupancy of nicotine receptors.