Analysis of the mechanism of the vasodepressor effect of urocortin in anesthetized rats.

The aim was to examine if the depressor effect of urocortin involves activation of the nitric oxide (NO)/L-arginine pathway, production of prostanoids or opening of K(+)-channels. I. v. bolus urocortin (0.1-3 nmol/kg) dose-dependently decreased mean arterial pressure in thiobutabarbital-anesthetized rats. The depressor effect of urocortin was unaffected by pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME, inhibitor of NO synthase, i.v. bolus) or noradrenaline (i.v. infusion), which increased arterial pressure to a similar level as that produced by L-NAME. In addition, methylene blue (inhibitor of soluble guanylyl cyclase, i.v. infusion), indomethacin (cyclooxygenase inhibitor, i.v. bolus), glibenclamide (blocker of ATP-sensitive K(+)-channels, i.v. bolus) or tetraethylammonium (a non specific K(+)-channel blocker, i.v. bolus) did not affect the depressor effect of urocortin. In conclusion, the depressor effect of urocortin in anesthetized rats is not mediated via the NO/L-arginine pathway, activation of soluble guanylyl cyclase, production of prostanoids, opening of TEA sensitive K(+)-channels nor opening of ATP sensitive K(+)-channels.