May 1, 1976

Pharmacological characterization of adrenergic receptors of a rabbit cerebral artery in vitro

The Journal of Pharmacology and Experimental Therapeutics
S P Duckles, J A Bevan

Abstract

In the light of controversy over the functional significance of the abundant sympathetic innervation of large cerebral blood vessels, an in vitro analysis of the adrenergic receptors mediating contractile effects in the rabbit basilar artery was undertaken. Beta adrenergic stimulation had no effect, and agents that block norepinephrine (NE) uptake did not alter contractile responses to l-NE. The l-NE dose-response curve could be resolved into two components S-shaped curves: the first had an ED50 OF 10(-5) M and reached a plateau at 10(-4) M; the second component continued above 10(-3) M without reaching a plateau. Phenylephrine and epinephrine dose-response curves were also biphasic; d-NE responses corresponded to the second phase of the l-NE curve. Relative potencies for the two components were different. For the first component, these were 1:0.23:0.18:0.03 for l-NE, epinephrine, phenylephrine and d-NE, respectively; relative potencies for the second component of the curve were 1:1:0.11:0.23. Phentolamine dissociation constants were analyzed separately for each component. The value for low l-NE concentrations was 5 X 10 (-8) M and, for higher concentrations, it was 3 X 10(-6) . The insensitivity of the alpha adrenergic recepto...Continue Reading

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Mentioned in this Paper

Arterial System
Depression, Chemical
Muscle Innervation, Function
Blood Vessel
Brain
Uptake
Adrenergic beta-Agonists
Norepinephrine, (+, -)-Isomer
Adrenergic alpha-Agonists
Nerve Supply

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