The actions of cirazoline on the rat vas deferens.
The pre- and postsynaptic effects of the alpha 1-agonist cirazoline were assessed in epididymal and prostatic portions of the rat isolated vas deferens. Cirazoline produced a postsynaptic alpha 1-adrenoceptor mediated potentiation of the isometric contraction to single pulse field stimulation in both prostatic and epididymal portions. In epididymal portions, nifedipine (10 microM) greatly attenuated the postsynaptic alpha 1-receptor mediated potentiation of nerve mediated contractions, uncovering a presynaptic inhibitory action of cirazoline . No evidence was found for alpha 2-antagonism by cirazoline . It is concluded that the previously reported antagonism of the presynaptic inhibitory effects of clonidine was due to postsynaptic potentiation of nerve-mediated responses by cirazoline .
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D007537:Isometric Contraction; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D009435:Synaptic Transmission / Q000187:drug effects; D014649:Vas Deferens / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D007093:Imidazoles; D009543:Nifedipine; D003000:Clonidine; C014282:cirazoline; D011224:Prazosin