Sites of actions of alpha 2 agonists in the brain and periphery.
Alpha 2 agonists including rilmenidine, clonidine and alpha methylnoradrenaline all seem to have a predominantly central action in lowering blood pressure. Studies using the peripheral decarboxylase inhibitor alpha-methyldopa hydrazine in both experimental animals and humans support the predominant central action of the active metabolite of methyldopa, alpha methylnoradrenaline. Comparative studies on the antihypertensive potency of selective alpha 2 agonists like rilmenidine, guanfacine, clonidine and lofexidine suggest that the relative ability to bind to alpha 1 and alpha 2 adrenoceptors is not critical but the ability to enter the central nervous system is essential for antihypertensive efficacy.
D000316:Adrenergic alpha-Agonists / Q000493:pharmacokinetics / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002230:Carbidopa / Q000493:pharmacokinetics / Q000494:pharmacology; D003000:Clonidine / Q000493:pharmacokinetics / Q000494:pharmacology; D003653:Decarboxylation; D008750:Methyldopa / Q000493:pharmacokinetics / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism; D011869:Radioligand Assay; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D018377:Neurotransmitter Agents; D011942:Receptors, Adrenergic, alpha; D008750:Methyldopa; D003000:Clonidine; D002230:Carbidopa