Similar localisation of alpha1- and beta-adrenoceptors in rabbit heart in relation to sympathetic nerve endings.
Electrically driven (1 Hz) rabbit papillary muscles were examined ex vivo for the localisation of the alpha1- and beta-adrenoceptor populations relative to the sympathetic nerve endings and to each other. We determined the influence of neuronal uptake blockade by cocaine upon the horizontal position of the dose-response curves for the inotropic and lusitropic effects exerted by noradrenaline in the presence of extra neuronal uptake blockade by hydrocortisone and in the presence and absence of adrenoceptor blockers. Cocaine similarly shifted the dose-response curves for both alpha1- and beta-adrenoceptors mediated effects to 10-30 times lower concentrations of noradrenaline. This potentiation by cocaine indicates that also the alpha1-adrenoceptor population is located close to or within the sympathetic synaptic clefts, as is known for the beta-adrenoceptor population.
Dybvik
T
T
Department of Pharmacology, University of Oslo, Norway.
Osnes
J B
JB
Skomedal
T
T
D000316:Adrenergic alpha-Agonists / Q000378:metabolism / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects / Q000294:innervation*; D006854:Hydrocortisone / Q000494:pharmacology; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects; D009411:Nerve Endings / Q000187:drug effects*; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D010210:Papillary Muscles / Q000187:drug effects; D011817:Rabbits; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D000893:Anti-Inflammatory Agents; D018765:Dopamine Uptake Inhibitors; D018340:Receptors, Adrenergic, alpha-1; D011943:Receptors, Adrenergic, beta; D003042:Cocaine; D006854:Hydrocortisone; D009638:Norepinephrine