Cardiac post-junctional alpha 1- and beta-adrenoceptors: effects of chronic chemical sympathectomy with 6-hydroxydopamine.
Alpha 1- and beta-adrenoceptor responsiveness and binding have been examined in cardiac tissues removed from guinea-pigs pretreated with 6-hydroxydopamine (6-OHDA) for 3 weeks. Results were compared with control tissues from sham-injected animals. Chemical sympathectomy with 6-OHDA resulted in an increase in the sensitivity of postjunctional beta-adrenoceptor-mediated responses to isoprenaline. No such increase was observed for the alpha 1-adrenoceptor-mediated responses to methoxamine. The increase in beta-adrenergic responsiveness was accompanied by a significant (P less than 0.05) 52% increase in the number of [3H]-dihydroalprenolol binding sites with no change in binding affinity. [3H]-Prazosin binding was not affected by pretreatment with 6-OHDA. The results suggest that cardiac beta- but not alpha 1-adrenergic responsiveness is regulated by the sympathetic innervation.
Chess-Williams
R G
RG
Department of Pharmacology, Welsh School of Pharmacy, University of Wales Institute of Science and Technology, Cardiff, U.K.
Broadley
K J
KJ
Sheridan
D J
DJ
D000818:Animals; D004082:Dihydroalprenolol / Q000378:metabolism; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D006892:Hydroxydopamines; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D016627:Oxidopamine; D011224:Prazosin / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D013563:Sympathectomy, Chemical; D013564:Sympathetic Nervous System / Q000502:physiology
D006892:Hydroxydopamines; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D016627:Oxidopamine; D011433:Propranolol; D008729:Methoxamine; D007545:Isoproterenol; D011224:Prazosin