Clinical and experimental pharmacology & physiology
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Clin. Exp. Pharmacol. Physiol. · May 1988
Inhibition of vasodilatation by methylene blue in large and small arteries of the dog hindlimb in vivo.
1. Injection of acetylcholine (ACh, 0.0005-2 micrograms/kg) or glyceryl trinitrate (GTN, 0.01-20 micrograms/kg) into the femoral artery increased femoral artery diameter, femoral blood flow and heart rate, and reduced femoral vascular resistance and systemic arterial blood pressure in anaesthetized dogs. The intravenous (i.v.) injection of ACh (2 micrograms/kg) produced a small decrease in systemic arterial pressure and an increase in heart rate, but did not dilate the hindlimb vessels. 2. ⋯ This selective potentiation of ACh-induced hypotension was not affected by autonomic ganglion blockade with hexamethonium (25 mg/kg, i.v.). 4. These results suggest that both ACh- and GTN-induced vasodilatation in vivo occurs through a mechanism involving guanylate cyclase activation in large arteries and resistance vessels in the dog hindlimb. Methylene blue inhibited the local vasodilator actions of ACh in the femoral vasculature despite potentiating the systemic depressor response to that agent.