Differential effects of prazosin and rauwolsin on the release of prostaglandins I2 and E2 from the perfused mesenteric arterial bed of the rabbit following nerve stimulation.

Sympathetic nerve stimulation of the perfused mesenteric arterial bed of the rabbit, in vitro, increases the secretion of prostaglandin (PG)I2 and PGE2. Prazosin (4.8 X 10(-6) M), an alpha 1 adrenergic receptor antagonist, inhibited this increase in release of PGI2 but not of PGE2 whereas rauwolsin (10(-7) M), and alpha 2 adrenergic receptor antagonist, inhibited the increase in release of PGE2 but not PGI2. Prazosin (10(-6) M) completely blocked the vasoconstrictor response to nerve stimulation, and to norepinephrine and phenylephrine administration, suggesting there to be little of an alpha 2 adrenergic receptor component in this response. It is concluded that the increase in PGI2 release allows the activation of alpha1 adrenergic receptors and is therefore post-junctional in origin, whereas the increase in PGE2 release following the activation of alpha 2 adrenergic receptors and may be pre- and/or post-junctional in origin.