Year: 1966
Type: article
Abstract: It is well established that morphine and other narcotic analgesics produce a mania-like behavioural condition in the cat accompanied by some signs reminiscent of sympathetic stimulation such as pupil dilatation and pilo-erection (Sollmann, 1957).Morphine given intravenously or intraventricularly into unanaesthetized cats also induces a remarkable hyperglycaemia.This effect is due to the stimulation of certain receptors in the central nervous system and is mediated through the peripheral sympathetic nervous system (Borison, Fishburn, Bhide & McCarthy, 1962).In spite of the foregoing findings regarding the sympathetic-like actions of morphine at certain sites in the body, this drug was claimed to cause a sustained fall in blood pressure and to have a "shock-like" effect in unaesthetized cats (Schmidt & Livingstone, 1933).No other reference has been found as to the effect of morphine on the blood pressure of such cats to elucidate this discrepancy.Therefore it seemed to be of interest to compare the changes in blood pressure of unanaesthetized cats with those of anaesthetized ones under uniform experimental conditions to get insight into the extent to which the blood pressure response to a centrally acting agent was modified by anaesthesia.(Since it is fairly common to make deductions about the action of a drug in the intact conscious animal on the basis of results obtained in the anaesthetized animal, this attempt is concerned with one of the current problems of pharmacology.)Morphine has been shown to cause a precipitous and sustained fall in the blood pressure of chloralose-anaesthetized cats when-given intravenously (Evans, Nasmyth & Stewart, 1952).Although we obtained a similar result, a different view of its mechanism of action will be presented here. METHODSCats of either sex, weighing between 2 and 4 kg, were used.Surgery was carried out during ether anaesthesia.The trachea was cannulated for artificial respiration.In cats in which the carotid occlusion response was to be tested both common carotid arteries were dissected from the surrounding tissues.All cats were vagotomized.A femoral vein was cannulated for injection of drugs.Coagulation of blood was prevented by injecting 5 mg/kg of heparin sodium intravenously.Blood pressure was recorded from the femoral artery on the same side as the cannulated femoral vein by a mercury manometer writing on smoked paper.The femoral nerve was cut as proximal as possible on this side.
Authors: S. O. KAYAALP, Ş. KAYMAKÇALAN
Institution: Ankara University
Language: English
Subfield: Cellular and Molecular Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2043923976