PT  - JOURNAL ARTICLE
AU  - Steinsland, O S
AU  - Furchgott, R F
TI  - Vasoconstriction of the isolated rabbit ear artery caused by nicotinic agonists acting on adrenergic neurons.
DP  - 1975 Apr 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 128--137
VI  - 193
IP  - 1
4099  - http://jpet.aspetjournals.org/content/193/1/128.short
4100  - http://jpet.aspetjournals.org/content/193/1/128.full
SO  - J Pharmacol Exp Ther1975 Apr 01; 193
AB  - In the perfused isolated central ear artery of the rabbit, nicotine, acetylcholine (ACh), tetramethylammonium (TMA) and carbachol (CCh) at high concentrations (greater than 1 mug/ml) produced transient vasoconstriction. The order of potency was: nicotine greater than ACh greater than TMA greater than CCh. Over the concentration range used, all of the agonists except ACh gave bell-shaped log concentration-response curves. Methacholine did not cause vasoconstriction. The response to ACh, TMA or CCh, but not to nicotine, was potentiated by atropine (0.1-1.0 mug/ml). Tetraethylammonium, hexamethonium, mecamylamine and d-tubocurarine blocked the response to the nicotinic agonists and to nerve stimulation. Ear arteries from reserpine-treated rabbits gave no, or very little, constrictor response to the nicotinic agonists or to nerve stimulation. These findings support the conclusion that the vasoconstriction produced by the nicotinic agonists is mediated by norepinephrine released from adrenergic nerve terminals as a result of the action of the agents on neuronal nicotinic receptors located at or near the terminals. The potentiation by atropine of the constrictor response to ACh, TMA and CCh is attributed to the blockade by atropine of neuronal muscarinic receptors on which these agonists act to inhibit the release of norepinephrine.