Alpha- and beta-adrenoceptors in the female dog urethra

The existence and subtypes of alpha- and beta-adrenoceptors in the female dog urethra were studied in vivo and in vitro by means of agonist and antagonist drugs. Noradrenaline, phenylephrine and B-HT 920, stimulants of alpha, alpha-1 and alpha-2 receptors respectively, caused an increase in the urethra tonicity. Thus indicating that the contractile activity is mediated by alpha-1 and alpha-2 adrenoceptors subtypes. On the other hand, the inhibitory urethral activity is under control of beta-adrenoceptors of beta-2 subtype, since the isoprenaline relaxing action is inhibited when beta-2 receptors are blocked, whilst this effect was not observed when beta-1 receptors were blocked. This fact was proved when beta-2 receptors were stimulated with salbutamol.