RESUMEN
The activities of the alpha-1 antagonist prazosin and alpha-2 antagonist yohimbine were evaluated against noradrenaline (NA), methoxamine (Me) and clonidine (Clo) on the reserpinized rat vas deferens. Prazosin antagonized competitively Me but not NA and Clo. On the other hand yohimbine showed a low and not competitive antagonism towards all the three agonists. Similar results were obtained when the antagonistic activities were tested in the presence of the alternative antagonist, in the attempt to isolate a single receptor population. We can conclude that the smooth musculature of the rat vas deferens contains prevalently alpha-1 adrenoceptors and a small population of NA activated receptors resistant to alpha-2 antagonists.
Asunto(s)
Agonistas alfa-Adrenérgicos/farmacología , Músculo Liso/efectos de los fármacos , Receptores Adrenérgicos/efectos de los fármacos , Reserpina/farmacología , Animales , Clonidina/farmacología , Interacciones Farmacológicas , Técnicas In Vitro , Masculino , Metoxamina/farmacología , Norepinefrina/farmacología , Prazosina/farmacología , Ratas , Ratas Endogámicas , Conducto Deferente/efectos de los fármacos , Yohimbina/farmacologíaRESUMEN
On the basis of results previously obtained from structural and theoretical studies on beta-adrenergic drugs, a series of aliphatic oxime ether derivatives (AOEDs) was synthesized. As expected, pharmacological in vitro tests showed that compounds examined exhibit a marked and competitive antagonism at beta-adrenoceptors; the beta 2/beta 1 selectivity ratio indicated that they are more active on the tracheal than on the cardiac beta-receptor. The chemical reactivity of the AOEDs was studied through the calculation of the electrostatic molecular potential (EMP) on a model compound in its preferred conformation. The results showed that the EMP trend agrees with that previously calculated for other beta-blocking drugs.
