Different effects of phenylephrine and clonidine on 86Rb efflux and on contraction in the rat caudal artery.
A large transitory efflux of 86Rb was induced by concentrations of phenylephrine (10(-6) and 10(-4)M) or clonidine (10(-4)M) which were able to produce phasic contraction. By contrast, a lower concentration of clonidine (10(-6) M), which could only induce a slower (tonic) contraction, only produced a weak but sustained 86Rb efflux. These results show qualitative and quantitative differences in the effects of the two alpha-agonists. They further support the view that phasic and tonic alpha-adrenergic responses may be related to different mechanisms.
D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology*; D011868:Radioisotopes; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism*
D011868:Radioisotopes; D010656:Phenylephrine; D012413:Rubidium; D003000:Clonidine