Effects of adrenoceptor agonists and antagonists on the firing of neurons in the rat A1 noradrenergic region.
Noradrenaline (NA), but not clonidine applied microiontophoretically, inhibited the firing of neurons in the rat A1 noradrenergic region, whereas intravenous clonidine dose-dependently inhibited their firing (ED50 = 18.3 micrograms/kg). The NA-induced inhibition was blocked by the beta-antagonist timolol, but not by the alpha-antagonists phentolamine or piperoxane. These results suggest that neurons in the A1 region possess beta-adrenoceptors rather than alpha-adrenoceptors near their cell bodies, and that systemically administered clonidine acts indirectly on these cells.
D000322:Adrenergic Agonists / Q000494:pharmacology*; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D005260:Female; D006892:Hydroxydopamines / Q000494:pharmacology; D008526:Medulla Oblongata / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009433:Neural Inhibition; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology / Q000502:physiology*; D016627:Oxidopamine; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000166:cytology / Q000502:physiology*; D013565:Sympatholytics / Q000494:pharmacology*
D000322:Adrenergic Agonists; D006892:Hydroxydopamines; D013565:Sympatholytics; D016627:Oxidopamine; D003000:Clonidine; D009638:Norepinephrine