Modulation of adrenergic responses by prostanoids in the isolated mesenteric vascular bed of the rat.

1. The influences of PGE2, PGE1, iloprost and carbocyclic thromboxane A2 (cTxA2) on the response to adrenergic nerve stimulation, exogenous noradrenaline and perfusion with methoxamine, have been compared in the rat mesenteric vascular bed. 2. PGE2, PGE1 and cTxA2 enhanced the vasoconstrictor response elicited by field stimulation, as well as that induced by noradrenaline and methoxamine. 3. Iloprost did not affect the increase in perfusion pressure induced by field stimulation, slightly reduced the vasoconstrictor response to high concentrations of noradrenaline, and significantly attenuated the increase in vascular tone induced by perfusion with methoxamine. 4. These findings suggest that, in the rat mesenteric vascular bed, prejunctional mechanisms are not involved in the interference exerted by different prostanoids on the vascular response to adrenergic activation.