Heterogeneous inhibitory effect of nitrendipine on 5-HT-responses in rabbit vascular tissues.
1. Sensitivity of 5-HT2 receptor mediated vascular responses to calcium channel antagonism was investigated in the rabbit thoracic aorta, common carotid artery and main pulmonary artery considering tissue-state of receptor reserve and agonist efficacy. 2. Although 5-HT2 receptor reserve seems to be similar in these preparations, nitrendipine had a heterogeneous inhibitory effect on the contractile response to 5-HT. 3. Reducing 5-HT2 receptor reserve by phenoxybenzamine caused an increase in the inhibitory effect of nitrendipine in these vascular tissues. 4. The vasoconstrictor response induced by 5-carboxyamidotryptamine (5-CT), which is a less potent agonist, showed greater sensitivity to nitrendipine antagonism than the response to 5-HT. 5. The results suggest that efficacy of agonists and tissue-state of receptor reserve seem to be important factors which are partially responsible for the inhibitory effect of nitrendipine on the contractile responses mediated by 5-HT2 receptors.
Gürdal
H
H
Department of Pharmacology, Medical School of Ankara University, Turkey.
Tulunay
F C
FC
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D002339:Carotid Arteries / Q000187:drug effects; D066298:In Vitro Techniques; D007650:Ketanserin / Q000494:pharmacology; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009568:Nitrendipine / Q000494:pharmacology*; D010643:Phenoxybenzamine / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects; D011817:Rabbits; D012701:Serotonin / Q000031:analogs & derivatives / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology*
D012702:Serotonin Antagonists; D010643:Phenoxybenzamine; D012701:Serotonin; C047087:5-carboxamidotryptamine; D007650:Ketanserin; D009568:Nitrendipine