ABSTRACT
Droperidol is used in the anaesthetic management of pheochromocytoma because of its sedative, anti-dysrhythmic and alpha-adrenoreceptor blocking properties. However, droperidol when used in pheochromocytoma, has been reported to produce a paradoxical hypertensive response. In vitro experiments with perfused rabbit ear arteries using a histochemical fluorescence technique, showed droperidol to be an inhibitor of noradrenaline uptake into sympathetic nerve endings, and this uptake inhibition was dose related. The uptake inhibition effect did not, however, produce pressor changes in experiments simulating pheochromocytoma in cats. The hypertensive response to droperidol may be due to blockade of presynaptic alpha-adrenoreceptors and this possible mechanism of action is discussed.
Subject(s)
Adrenal Gland Neoplasms/physiopathology , Droperidol/adverse effects , Hypertension/chemically induced , Pheochromocytoma/physiopathology , Animals , Blood Pressure/drug effects , Cats , Dose-Response Relationship, Drug , Female , Male , Nerve Endings/metabolism , Norepinephrine/metabolism , RabbitsABSTRACT
An examination of sections of the central artery of the rabbit external ear with the transmission electron microscope revealed a single and uniform population of axons near the medial-adventitial border. The dimensions of the neuromuscular cleft (mean closest distance 0.5 micrometer) and of the approaches between smooth muscle cells (not less than 20 nm) were determined. On the basis of the morphology of the neuronal vesicles and their ability to take up 5-hydroxydopamine the axons were classified as adrenergic, confirming previous light-microscopic histochemical observations. The axons also exhibited a weak but definite acetylcholinesterase activity in association with their sxon membrane, as shown by a histochemical technique.
Subject(s)
Adrenergic Fibers/ultrastructure , Arteries/innervation , Ear, External/blood supply , Rabbits/anatomy & histology , Acetylcholinesterase/metabolism , Adrenergic Fibers/enzymology , Animals , Axons/ultrastructure , Butyrylcholinesterase/metabolism , Female , Histocytochemistry , Hydroxydopamines/pharmacology , Male , Muscle, Smooth/innervationABSTRACT
The response of an isolated artery preparation to commercial local anaesthetic solutions containing either prilocaine or lignocaine in the presence of adrenaline or noradrenaline has been examined. In low doses, both local anaesthetics were found to augment the constrictor response to adrenaline, wheras at higher doses the effect of adrenaline was significantly depressed by them. In contrast, noradrenaline's vasoconstrictor response was not potentiated by low doses of lignocaine, although higher dose levels caused a significant reduction in its vasoconstrictor effect.
Subject(s)
Anesthetics, Local/pharmacology , Ear, External/blood supply , Vasoconstriction/drug effects , Animals , Arteries/drug effects , Dose-Response Relationship, Drug , Drug Combinations , Epinephrine/pharmacology , Lidocaine/pharmacology , Norepinephrine/pharmacology , Prilocaine/pharmacology , RabbitsABSTRACT
The basic mechanisms responsible for effects of vasoconstrictors in local anaesthetic solutions are not fully understood. In this paper the interactions of the various ingredients of local anesthetic solutions are considered. Some of the author's work in this field is summarised and current research is discussed.
