No abstract

No abstract

During routine estimations of catecholamines in human urine by the spinal-cat blood pressure method, it appeared that male cats showed greater pressor responses to catecholamines than female cats. We therefore studied the effect of testosterone treatment on the pressor response to noradrenaline. Desmethylimipramine was also employed to obtain further enhancement of the pressor response. METHODSThe results of the present study were obtained from 50 male and 19 female spinal cats weighing between 1.8-4.8 kg. Fifty-five cats were routinely anaesthetized by intraperitoneal injection of pentobarbitone sodium (30-35 mg/kg) and the spinal cord was then transected. In 14 cats the spinal transection was done under ether anaesthesia and the ether allowed to blow off. The femoral vein of one side was cannulated with an in-dwelling polyethylene cannula for administration of noradrenaline. Arterial blood pressure was recorded from the left common carotid artery by means of a mercury manometer and kymograph. All cats were bilaterally vagotomized and maintained on positive pressure artificial restiration. The spinal cord was exposed by laminectomy and two sutures were passed under the cord at the level of the second cervical vertebra. The cord was then transected between the sutures. After cord transection, the animals were allowed a rest period of 1 hr during which time the blood pressure became steady between 60 and 90 mm Hg.In each experiment the minimal amount of noradrenaline required to elicit a detectable pressor response was determined. Subsequently, increasing doses of noradrenaline were injected every 4 min until a near maximal response was obtained. This provided one set of observations. In some cats when more than one set of observations was obtained, a period of 30 min rest was allowed between consecutive sets of observations. Testosterone aqueous adsorbate (Aquaviron, Indian Schering) was administered to some cats intramuscularly in a single dose of 10 mg/kg, and these cats were used for the study on the second, third, fourth, fifth, sixth, seventh or ninth days after injection.Desmethyl-imipramine (3 mg/kg) was administered to some cats intravenously 15 min before recording responses.Solutions of noradrenaline were freshly prepared and kept in ice.Analysis of data The heights of the maximal pressor responses to noradrenaline in all the sets of observations in the control cats were measured and their mean calculated. This was the control average maximal

No abstract