Sympathetic a‐adrenergic control of large‐bore arterial vessels, arterioles and veins, and of capillary pressure and fluid exchange in whole‐organ cat skeletal muscle

Abstract

The sympathetic nervous control of the vascular bed of cat gastrocnemius muscle was studied with a new whole-organ technique which permits simultaneous, continuous and quantitative measurements of capillary pressure (Pc), capillary fluid exchange and resistance reactions in the whole vascular bed and in its three consecutive sections: large-bore arterial vessels (greater than 25 microns), arterioles (less than 25 microns) and veins. The results demonstrated a distinct neural control of all three consecutive vascular sections, graded in relation to the rate of nerve excitation up to maximum at 16 Hz. Stimulation at high rates, which in the steady state caused an average rise of overall regional resistance from 15.3 to 120 PRU (7.8-fold increase), thus raised large-bore arterial vessel resistance from 8.8 to 64 PRU (7.3-fold increase), arteriolar resistance from 4.5 to 49 PRU (10.9-fold increase) and venous resistance from 2.0 to 7 PRU (3.5-fold increase). The rate of resistance development (PRUs-1) of the sympathetic constrictor response was much higher in the arteriolar than in the other sections, which indicates that the neural control is especially prompt and efficient in the arterioles. A passive component was shown to contribute to the described responses only on the venous side, but in no case by more than 10% of the total sympathetic venous resistance response, which thus is mainly active. Of special functional importance was that the new technique provided information about the adrenergic control of Pc in absolute figures. From the control value of 19 mmHg, graded sympathetic stimulation caused a graded decline in Pc, at maximum constriction by about 7 mmHg. This resulted in marked net transcapillary fluid absorption, in turn increasing plasma volume.

Elevated Brain Serotonin Turnover in Patients With Depression

“…Patients with MDD were moderately to severely depressed with a mean (SD) HAM-D score of 25 (4) and a mean (SD) BDI score of 29 (8). They also had high levels of both state (mean [SD] score, 57 [12]) and trait (mean [SD] score, 62 [7]) anxiety.…”

Effects of selective ETB‐receptor stimulation on arterial, venous and capillary functions in cat skeletal muscle

“…This response was also associated with a decrease in capillary pressure which seemed to be more pronounced per unit resistance increase than that to most other vasoconstrictors, e.g. neurally released noradrenaline (Maspers et al, 1990a). As indicated by the observed decrease in CFC, this response further involved a maintained constriction of the terminal arterioles/precapillary sphincters, and a consequent reduction of the size of the functional capillary surface area.…”

Norepinephrine responses in rat renal and femoral veins are reinforced by vasoconstrictor prostanoids

“…Differences in the adrenergic innervation density between the various compartments that compose the venous bed may justify these regional variations of response [6][7][8]. On the other hand, these heterogeneous responses may also be due to differences in the distribution of adrenoceptors.…”