SOMATOSTATIN-INDUCED INHIBITION OF NEUROTRANSMISSION IN THE MOUSE ISOLATED VAS-DEFERENS IS RESISTANT TO PERTUSSIS TOXIN

The potential effects of pertussis toxin pretreatment on the inhibitory effect of somatostatin (SRIF) and the selective SRIF receptor agonist, seglitide, were studied in mouse vas deferens and these were compared with its effect on the negative chronotropic action of carbachol in mouse atria. Somatostatin and seglitide caused a concentration-dependent inhibition of neurogenically mediated contractile responses in the vas deferens (EC(50) values of 15 and 0.6 nM respectively). There was no difference in their potencies in preparations removed from pertussis toxin pretreated mice. In contrast, the negative chronotropic action of carbachol in mouse atria was abolished by pretreatment with pertussis toxin. We conclude that, in contrast to muscarinic receptor activation in mouse atria, the inhibitory effect of somatostatin in the vas deferens is not mediated by a pertussis toxin sensitive G-protein. The high potency of seglitide suggests that the SRIF receptor involved is of the SRIF, type.