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Biomedical subjects

R F WHELAN

Publications and source records attributed to R F WHELAN.

At least 19 recordsLinked to original sources
PubMed1964

THE EFFECTS OF BETHANIDINE ON THE PERIPHERAL CIRCULATION IN MAN.

Bethanidine has been administered intra-arterially and intravenously into normotensive subjects and its effects on the limb blood vessels, arterial blood pressure, vascular sensitivity to noradrenaline and the degree and time course of sympathetic nerve blockade have been studied. The drug caused an initial constriction of hand and forearm vessels which is attributed to release of catechol amines since it is abolished by the prior administration of phenoxybenzamine. The constriction was followed by a sustained vasodilatation lasting between 5 and 20 hr. Sympathetic blockade of hand vessels commenced immediately on infusion and was complete within 1 hr of administration. Recovery occurred in about 5 hr. Sensitivity to intra-arterial noradrenaline was increased within 10 to 15 min of infusion and before sympathetic blockade was complete. Intravenous administration caused a slight rise in blood pressure of supine subjects. Baroreceptor reflex responses of heart and of limb vessels elicited by tilting the subject feet downwards were abolished by bethanidine and postural hypotension occurred. Bethanidine is a potent sympathetic blocking agent in man with properties intermediate between those of bretylium and guanethidine.

Antihypertensive Agents↗
PubMed1963

EFFECTS OF BRETYLIUM AND GUANETHIDINE ON HUMAN HAND AND FOREARM VESSELS AND ON THEIR SENSITIVITY TO NORADRENALINE.

Infusions of bretylium and guanethidine into the brachial artery of normal subjects caused a fall in forearm and hand blood flow followed by a sustained increase in flow. The constrictor phase was attributed to catechol amine release since it was blocked by phenoxybenzamine. A slight and transient increase in response of the hand vessels to noradrenaline was seen after bretylium in the early constrictor phase before sympathetic block was complete. Guanethidine produced a more definite and sustained increase in the response of the hand vessels to noradrenaline. It is concluded that the phenomenon of tolerance which is conspicuous with bretylium and negligible with guanethidine is unlikely to be due to the rapid onset of hypersensitivity of the peripheral vessels.

Autonomic Nerve Block↗
PubMed1962

Effect of hexamethonium on the vascular response to noradrenaline in man.

Intra-arterial infusion of hexamethonium into the brachial artery had no potentiating effect on the constrictor response of the vessels of the forearm or hand to noradrenaline given by the same route. The response of the hand vessels to intravenous infusion of noradrenaline was enhanced after intra-arterial hexamethonium, but this was attributed to entry of the blocking agent into the general circulation resulting in blockade of baroreceptor reflexes since the potentiation was seen to an equal degree on both sides. It is concluded that if increased sensitivity to noradrenaline plays a part in the phenomenon of tolerance to hexamethonium this must be a slowly developing effect.

Blood Vessels↗