title: The use of neurally released agonist in the measurement of antagonism at alpha-adrenoceptors.
abstract: Graded contractile responses of the rat vas deferens were obtained to trains containing varying numbers of pulses delivered transmurally at 500 Hz, allowing construction of pulse-response curves. In the presence of postjunctional adrenoceptor blocking drugs, these curves were displaced to the right in a parallel manner, allowing the estimation of pA2 values for the drugs. Activity of drugs at prejunctional adrenoceptors was estimated from the reduction of inhibition of the response to a second pulse delivered 3 s after trains containing different numbers of pulses. It is suggested that the technique is more physiological than others used to determine the antagonistic activity of drugs at adrenoceptors.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009451:Neuroeffector Junction / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*
chemical_list: D000317:Adrenergic alpha-Antagonists; D018377:Neurotransmitter Agents; D011942:Receptors, Adrenergic, alpha