Affiliation:
1. Department of Pharmacology, University of California Los Angeles, School of Medicine, Center for the Health Sciences, Los Angeles, California 90024
Abstract
The effects of α-receptor-blocking agents on the contractile responses of isolated rabbit arteries to sympathetic nerve stimulation and exogenous
l
-norepinephrine (
l
-NE) were compared. In the pulmonary artery and aorta, yohimbine, phentolamine, and phenoxybenzamine blocked the response to nerve stimulation less than that to an equipotent dose of
l
-NE. This resistance of neurogenic response was independent of the frequency and number of stimuli and persisted after inhibition of the nerve
l
-NE uptake by cocaine. The neurogenically released transmitter
l
-NE probably forms a high concentration near the adventitia-media junction, whereas the exogenous NE is distributed evenly throughout the thickness of media. Thus higher concentrations of α-receptor-blocking agents would be needed to block the effect of neurogenic
l
-NE than to block that of exogenous
l
-NE. This explanation of the resistance was thought to be more appropriate to the large vessels tested than that based on neuroeffector proximity.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
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