1 A new technique for determining venous compliance at a standardized congestion pressure has been developed based on the optical method described by Nachev, Collier & Robinson (1971). It uses a linear variable differential transformer for a direct and continuous recording of venous compliance. 2 This method has been used to establish dose‐ response curves for the constrictor effects of noradrenaline, adrenaline, 5‐hydroxytryptamine and dihydroergotamine after direct local infusion. 3 A parallel shift to the right of the noradrenaline dose‐response curves was observed after local infusion of phentolamine, showing that the method can be used also to study interactions between agonists and antagonists on human veins in vivo. The usefulness of this technique for investigating the effects of orally administered drugs has also been established. The venoconstrictor action of dihydroergotamine reached its maximum after 1.5 h and remained almost constant for the period of observation (8 h).

1 Venous resistance contributes very little to total peripheral resistance; more than half of the total blood volume, however, is contained in the extrathoracic veins.Owing to marked differences between venous and arterial anatomy and physiology, studies on veins and arteries usually require different methodological approaches. Whereas for arteries the most relevant parameters are resistance, pressure and flow, for veins volume and compliance are most important. For studies of general aspects of the peripheral circulatory system, venous occlusion plethysmography is probably the most useful method. The determination of both the rate of rise in limb volume and the total volume rise after inflating a proximally applied occlusion cuff to a subdiastolic pressure permits the concomitant estimation of both arterial flow and venous compliance.

No abstract

The beta‐adrenoceptor blocking activities of pindolol and propranolol have been investigated in healthy male volunteers. Pindolol was about forty times more potent than propranolol in reducing isoprenaline‐ induced tachycardia. Pindolol (5 mg) and propranolol (u99 mg) were approximately equiactive in reducing exercise‐induced tachycardia, 2 h after oral administration. The duration of action of pindolol is significantly longer than that of propranolol; 24 h after pindolol (kmg), 36+/‐5% of the masimum effect were still present, and after propranolol (100 mg) 16+/‐4% remained. Despite the long duration of action of pindolol, there was no evidence for cumulation during oral administration of 5 mg t.d.s. for 5 days.

No abstract