Functional separation of adrenergic and cholinergic fibers to skeletal muscle vessels

Role of endogenous prostaglandins in regulation of uterine blood flow and adrenergic neurotransmission

Earlier studies from these laboratories have demonstrated that prostaglandins (PG's) of the A and E series are potent uterine vasodilators whereas PGF's do not significantly alter uterine vascular resistance. In addition, PGE's and PGF's are also able to modify adrenergic vasoconstrictor responses in the canine uterus. In the present study the role of endogenous prostaglandins in regulating uterine vascular resistance and adrenergic neurotransmission was evaluated. Intra-arterial infusion of the prostaglandin synthesis inhibitor meclofenamate resulted in a significant reduction in PGE levels in uterine venous plasma and increased vascular resistance. Uterine vasoconstrictor responses produced by sympathetic nerve stimulation and norepinephrine were enhanced when endogenous PG synthesis was inhibited. During sympathetic nerve stimulation, uterine venous plasma levels of radioimmunoassayable prostaglandins of the E of F series did not change, suggesting that the adrenergic activation of PG synthesis is not detectable in uterine venous efferent. These data suggest that endogenous prostaglandins of the E series appear to play an important role in regulating uterine blood flow (I) by relaxing uterine vascular smooth muscle and (2) by depressing adrenergic vasoconstrictor responses.

Hypothalamic control of the distribution of cardiac output in the unanesthetized rhesus monkey

Regional organ blood flow and resistance changes evoked after 10 minutes of electrical stimulation of pressor areas in the anterior hypothalamus were studied in six unanesthetized, restrained rhesus monkeys. Five other monkeys served as controls. The regional changes produced by stimulus intensities which did not affect systemic arterial pressure, central venous pressure, cardiac output, or pulse rate were similar to those produced by the stimulations at higher levels which significantly increased the levels of these variables. With both low and high levels of stimulation the fractions of cardiac output to skeletal muscle and chest wall were increased 51 and 146% at the expense of the output to the kidneys, skin, stomach, spleen, pancreas, mesentery, and thyroid which decreased 38 to 79%. In each of two monkeys tested, the marked rise in blood flow and vasodilatation of skeletal muscle was only slightly affected by atropine. Therefore, there is at least some hypothalamic control over skeletal muscular vasodilatation in the unanesthetized monkey that is not cholinergically mediated.