Limb vascular resistance

Somljo Is there anyone here who has done old-fashioned hind limb vascular resistance experiments. 

Verapamil s major effect is on the slow Ca channel. The result is a slowing of AV conduction and the sinus rate. This inhibition of the action potential inhibits one limb of the reentry circuit believed to underlie most paroxysmal. supraventricular tachycardias that use the A V node as a reentry point. It is categorized as a class IV antiarrhythmie drug (see Classes of Antiarrhythmie Drugs" below). Hemodynami-cally. verapamil causes a change in the preload, afterload, contractility, heart rate, and coronary blood flow. The drug reduces systemic vascular resistance and mean blood pressure, with minor effects on eardiae output. 

In doses as low as 5 pg/kg, ryanodine (I), whose structure was recently elucidated, significantly increased vascular resistance in cat hind limb, spleen and tissues of the head and neck O.. The vasoconstrictor action was selective, however, in that much larger doses were required to increase resistance in the kidney, while that of the superior mesenteric vascular bed was unchanged or decreased O. The vasoconstrictor action of ryanodine may be mediated centrally20. 

In contrast angiotensin II displayed a strong vasoconstriction effect on the same vascular district. In our experiments as in those of White and Ross ( ) on cats, angiotensin reduced vascular resistance in the hind limb of the dog. 

The predominant actions of phenylephrine are on the cardiovascular system. Parenteral administration causes a rise in systolic and diastolic pressures due to peripheral vasoconstriction. Accompanying the pressor response to phenylephrine is a marked reflex bradycardia that can be blocked by atropine after atropine, large doses of the peripheral resistance is considerably increased. Circulation time is slightly prolonged, and venous pressure is slightly increased venous constriction is not marked. Most vascular beds are constricted renal, splanchnic, cutaneous, and limb blood flows are reduced, but coronary blood flow is increased. Pulmonary vessels are constricted, and pulmonary arterial pressure is raised. 

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