title: Contractile responses to adrenergic nerve stimulation are enhanced with removal of endothelium in rat caudal artery.
abstract: Removal of the endothelium from isolated perfused rat caudal arteries produced a two fold increase in the contractile response to transmural nerve stimulation. Pretreatment with 6-hydroxydopamine eliminated the contractile response to adrenergic nerve stimulation but failed to uncover any vasodilatory effect of electrical stimulation, either directly on smooth muscle or via non-adrenergic nerves. Endothelial removal also produced two and four fold enhancement of the contractile responses to the selective alpha 1- and alpha 2-adrenoceptor agonists methoxamine and B-HT 920. However, pKB values for prazosin and yohimbine versus both agonists indicate that both methoxamine and B-HT 920 are acting primarily at alpha 1-adrenoceptors in this tissue. These results provide evidence that endothelial factors released either at basal levels or by the stimulation of agonists play a significant physiological role in modifying the contractile responses of blood vessels.
mesh_terms: D000316:Adrenergic alpha-Agonists; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D004558:Electric Stimulation; D004730:Endothelium, Vascular / Q000502:physiology*; D006892:Hydroxydopamines / Q000494:pharmacology; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000294:innervation* / Q000502:physiology; D016627:Oxidopamine; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D001381:Azepines; D006892:Hydroxydopamines; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D013779:Tetrodotoxin; C024763:talipexole; D016627:Oxidopamine; D008729:Methoxamine; D011224:Prazosin