Prejunctional actions of some beta-adrenoreceptor antagonists in the vas deferens preparation of the guinea-pig.
1. The beta-adrenoceptor antagonists propranolol, pronethalol, MJ 1999 and Ciba 39089-Ba reduced responses to field stimulation of the guinea-pig isolated vas deferens preparation without significantly affecting responses to exogenously added noradrenaline.2. This prejunctional blocking action of the drugs cannot be correlated with their action as beta-adrenoceptor antagonists or non-specific depressants.3. The blockade produced was more pronounced at low (5-20 Hz) than at high (50 Hz) frequencies of stimulation.4. The blockade was slow in onset, and once established was poorly reversed by washing the preparation over a period of 1 to 2 h.5. The blockade produced could be reversed by dexamphetamine and cocaine.6. These experiments suggest that the beta-adrenoceptor antagonists may have some actions which closely resemble those of the adrenergic neurone blocking agent guanethidine.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000605:Amino Alcohols / Q000494:pharmacology; D000813:Anilides / Q000494:pharmacology; D000818:Animals; D003042:Cocaine / Q000494:pharmacology; D003913:Dextroamphetamine / Q000494:pharmacology; D004558:Electric Stimulation; D004983:Ethanolamines / Q000494:pharmacology; D006145:Guanethidine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D013451:Sulfonic Acids / Q000494:pharmacology; D013565:Sympatholytics / Q000494:pharmacology*; D014649:Vas Deferens / Q000187:drug effects*
D000319:Adrenergic beta-Antagonists; D000605:Amino Alcohols; D000813:Anilides; D004983:Ethanolamines; D013451:Sulfonic Acids; D013565:Sympatholytics; D011433:Propranolol; D003042:Cocaine; D003913:Dextroamphetamine; D009638:Norepinephrine; D006145:Guanethidine