DEPRESSION OF THE VASOMOTOR CENTRE BY MECAMYLAMINE, INDEPENDENT OF ITS GANGLION-BLOCKING ACTIVITY

Mecamylamine depressed the vasomotor centre independently of its ganglion-blocking action. The central action was elicited by small amounts of the drug when it was confined to the central nervous system of dogs and cats anaesthetized with pentobarbital sodium and of spinal cats. The spinal site of action was shown by the inhibition of vasomotor responses due to spinal compression in cats, when mecamylamine was introduced intrathecally in a dose too small to block autonomic ganglia. The supraspinal site of action was shown by intravertebral arterial injection of mecamylamine into cats, which caused hypotension and selectively blocked the electrically evoked pressor responses from the medulla without affecting the "nicotinic" ganglionic responses to acetylcholine. Injection of mecamylamine into the cerebral ventricles of dogs produced hypotension, and the reflex vasomotor responses to stimulation of afferent fibres in the vagus nerves and to occlusion of the common carotid arteries were inhibited without any change in the response of the nictitating membrane to preganglionic nervous stimulation.

Quantitative study of intestinal fluid loss in irreversible hemorrhagic shock

The effect of circulatory hypotension on the small intestine was studied in 42 dogs. The small intestine was clamped at the gastric and ileocecal ends, and the dogs were subjected to control studies or to hypotension of 30 or 40 mm Hg, with and without Dibenzylene, atropine, or vagotomy. The dry gut weight, the wet gut weight, the lumen contents, and the survival time were measured. The increase in gut weight was related entirely to the accumulation of fluid in the lumen of the gut. Vagotomy did not reduce the quantity of fluid in the gut lumen, but Dibenzylene reduced the amount and atropine abolished the accumulation of fluid. It is suggested that local irritation of the gut by anoxia causes secretion of fluid and hypermotility of the gut.

The use of ethamivan in the treatment of barbiturate poisoning

Ethamivan was used as a respiratory analeptic in the treatment of nine cases of severe barbiturate poisoning. Initial intravenous injections of 100 to 150 mg. of ethamivan increased the depth of respirations within a minute. Prolonged respiratory stimulation was achieved by a continuous intravenous infusion of 500 to 3000 mg. of ethamivan per litre of fluid. If hypotension occurred, an intravenous drip of noradrenaline was used; fluid overloading was avoided by adjusting the concentrations of drugs given, so that no more than a total of 125 c.c. of fluid per hour was administered. The chief side effect of overdosage of ethamivan was muscular twitching. This did not prove to be a problem and was of some value in determining the amount of drug given. The nine patients survived. It was concluded that ethamivan is a useful agent in the treatment of barbiturate poisoning.