Some bases of differences in vascular response to sympathetic activity.

Abstract

IN 1858 Claude Bemarde summarized much of his research into the physiology of the control of the circulation by the statement that the sympathetic nervous system acted as a "vasoconstrictor nerve." Subsequent study has shown that this division of the autonomic nervous system, although not always constrictor, exerts a control over the tone of both arteries and veins, which is of profound physiological significance. The influence on a particular vascular segment, however, varies widely, both qualitatively and quantitatively, according to its location within the vascular tree.In this brief review, three general patterns of sympathetic control of vascular tone are described (Fig. 1). These are patterns of neuromuscular organization and are distinguished on the basis of both anatomical and functional criteria derived from in vitro studies. They are specific types of relationships between the contractile system of the blood vessel wall, particularly the individual vascular smooth muscle cells, and the postganglionic adrenergic neural terminations. Their adequate description includes a detailed consideration of the transmitter mechanism that links the two types of cells. In general, these patterns vary with vessel diameter and function. In each instance the different neuromuscular organization reflects a different functional role of the blood vessel. Although for convenience, three basic patterns of neuroeffector organization are presented, these are disparate examples selected from the two extremes and probably the middle of a wide-ranging continuum. They have been recognized by parallel structural and functional investigation, the results of which complement each other.

Lower capacitance response and capillary fluid absorption in women to defend central blood volume in response to acute hypovolemic circulatory stress

“…In small muscular arteries and arterioles, the distance between sympathetic nerve endings and smooth muscle cells is short, and responses to NE are fast and initially great but not maintained over time. In larger arteries, the distance between synapses and smooth muscle cells is greater, and since NE relies both on diffusion and neuronal reuptake within the vessel wall, this results in a slower and smaller response but is maintained over time (3). It may be hypothesized that women primarily rely to a larger extent on arterial vasoconstriction of smaller arteries, i.e., fast but not maintained, whereas men rely on vasoconstriction in larger arteries with slower but maintained responses over time (3,31).…”

“…In larger arteries, the distance between synapses and smooth muscle cells is greater, and since NE relies both on diffusion and neuronal reuptake within the vessel wall, this results in a slower and smaller response but is maintained over time (3). It may be hypothesized that women primarily rely to a larger extent on arterial vasoconstriction of smaller arteries, i.e., fast but not maintained, whereas men rely on vasoconstriction in larger arteries with slower but maintained responses over time (3,31). The more pronounced return in FBF during LBNP and the initially faster but less maintained arm capacitance response as well as decreased net capillary fluid absorption in women support this theory (Figs.…”

Hyperreactivity of coronary arterial smooth muscles in response to ergonovine from rabbits with hereditary hyperlipidemia.

“…Since ergot alkaloids, such as ergotamine and ergonovine, have complex pharmacological properties with potential actions at dopaminergic and serotonergic as well as a-adrenergic receptors (MiillerSchweinitzer and Weidmann, 1978), and arteries from different vascular beds are pharmacologically heterogeneous (Bevan, 1979), it is important to clarify the nature of the contractile response to ergonovine of arteries from different vascular beds. Irr recent studies, we have demonstrated that atherosclerotic aortas from rabbits fed a high-cholesterol diet are supersensitive to the constrictor effects of ergonovine (Henry and Yokoyama, 1980).…”

The potential use of flavonoids as venoactive drugs and the role of citrus fruits

“…The action mechanisms are not well established [6,10,11] and not clearly understandable theoretically. The smooth muscles (SM) of large and medium-sized veins studied in vitro had no tone and did not relax under the impact of vasodilators [12]. The lumen of collapsed veins is slit-like, the circular SM layer is thin, bunches of SM alternating with connective tissue.…”