ALPHA-ADRENOCEPTORS AND BETA-ADRENOCEPTORS IN THE FEMALE DOG URETHRA

The existence and subtypes of .alpha.- and .beta.-adrenoreceptors 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 inhibitor 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.