Role of ganglionic M-1 and M-2 receptors in the neuronal control of the cardiovascular system of the normotensive rat as determined with pilocarpine.
The adrenoceptors involved in the increase in diastolic pressure and heart rate elicited by i.v. administration of pilocarpine to the pithed rat were assessed using as pharmacological tools the alpha 1-adrenoceptor antagonist prazosin, the alpha 2-adrenoceptor antagonist rauwolscine, the beta 1-adrenoceptor blocker atenolol and the beta 2-adrenoceptor blocker ICI 118,551. Pilocarpine indirectly activated vascular alpha 1- and cardiac beta 1-adrenoceptors. By using the M-1 antagonist pirenzepine and the mixed M-1/M-2 antagonist dexetimide, pilocarpine was shown to be a mixed M-1/M-2 agonist. Pilocarpine initiated antagonistic effects on intrasynaptic alpha 2-adrenoceptor-mediated pressor responses and not on those triggered by extrasynaptic alpha 2-adrenoceptors. During vasopressin infusion to counteract a possible vasodilator action of pilocarpine, it was demonstrated that pilocarpine indirectly activated alpha 1- and alpha 2-adrenoceptors. The results support the hypothesis that intra- and extrasynaptic alpha 2-adrenoceptors comprise different populations and that the neuronal control of alpha 2-adrenoceptors is mediated by ganglionic M-2 receptors.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects / Q000294:innervation*; D003971:Diastole; D005724:Ganglia / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D010862:Pilocarpine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D014667:Vasopressins / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D010862:Pilocarpine; D014667:Vasopressins