Postsynaptic spinal alpha-adrenoceptors mediate effects of intrathecal clonidine.
The cardiovascular effects of intrathecal administration of clonidine were examined after depletion of spinal cord noradrenaline or 5-hydroxytryptamine by pretreatment with 6-hydroxydopamine or 5,6-dihydroxytryptamine. Despite marked reduction in spinal noradrenaline or 5-hydroxytryptamine levels, resting blood pressure and heart rate were unchanged and the clonidine-induced hypotension and bradycardia were unimpaired. The results suggest that intrathecal clonidine acts via inhibitory spinal alpha-adrenoceptors located postsynaptically on the preganglionic nerve cell bodies.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D007278:Injections, Spinal; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000032:analysis*; D011942:Receptors, Adrenergic, alpha / Q000032:analysis*; D013116:Spinal Cord / Q000032:analysis*
D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D003000:Clonidine