Clonidine-induced desensitization differentiates presynaptic alpha-2 adrenoceptors of the guinea-pig ileum and rat vas deferens.
Clonidine-induced inhibitions of twitch responses of coaxially stimulated guinea-pig ileum and transmurally stimulated rat vas deferens were antagonized by yohimbine in a competitive manner. In contrast to rat vas deferens, clonidine caused desensitization of presynaptic alpha 2-adrenoceptors on cholinergic neurons of guinea-pig ileum. Cross desensitization was observed between clonidine and oxymetazoline. No cross desensitization between clonidine and morphine was observed and indicates that presynaptic alpha 2-adrenoceptors are involved in clonidine-induced desensitization of the presynaptic site in the guinea-pig ileum.
Ilhan
M
M
Long
J P
JP
D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D010109:Oxymetazoline / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D010109:Oxymetazoline; D003000:Clonidine