Effect of adrenalectomy and demedullation of the adrenals on vasopressor responses to stimulation of postjunctional alpha 2-adrenoceptors.
After adrenalectomy performed 18-12 h previously, the vasopressor responses induced by stimulation of postjunctional alpha 2-adrenoceptors (agonist: B-HT 920) were attenuated in pithed normotensive rats in contrast to pressor responses mediated by postjunctional alpha 1-adrenoceptors (agonist: cirazoline). Aldosterone and desoxycorticosterone both enhanced the vasopressor responses to the alpha 2-adrenoceptor agonist B-HT 920 in adrenalectomized rats, but did not fully restore the effects. Demedullation of the adrenals also attenuated the vasoconstrictor processes evoked by stimulation of postjunctional alpha 2-adrenoceptors 18-22 h later. This effect was reversed after an infusion with adrenaline. The combination of aldosterone and adrenaline produced full recovery of the increase in diastolic pressure elicited via alpha 2-adrenoceptors in adrenalectomized (18-22 h) animals. The results suggest that circulating adrenaline and aldosterone (or corticosterone) are required for optimal functioning of vascular postjunctional alpha 2-adrenoceptors.
D000305:Adrenal Cortex Hormones / Q000494:pharmacology; D000315:Adrenalectomy; D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D003900:Desoxycorticosterone / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D012739:Gonadal Steroid Hormones / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*
D000305:Adrenal Cortex Hormones; D001381:Azepines; D012739:Gonadal Steroid Hormones; D007093:Imidazoles; D011942:Receptors, Adrenergic, alpha; D003900:Desoxycorticosterone; D000450:Aldosterone; C024763:talipexole; C014282:cirazoline; D004837:Epinephrine