Abstract
The subcutaneous or intraperitoneal injection of 10 to 15 mg. of morphine sulphate per 100 gm. of body weight, causes under normal circumstances, no perceptible change in the size of the pupil of the albino rat. Such doses of morphine produce a state of catalepsy and stiffness of the tail in the experimental animal and abolish the corneal reflex.
To such morphinized animals several mydriatics were administered by different routes. At first, only sympathetic stimulants were used. Normal-control and morphinized rats were each given intermuscular injections of cocaine hydrochloride 10 mg. per 100 gm. of body weight. Solutions of cocaine (1:50), of adrenalin hydrochloride (1:1000), and of ephedrine sulphate (1:100) were instilled in the conjunctival sac. (In every series of experiments 12 rats were used.) These installations, or injections, produce no, or only slight, dilatation of the pupil in the normal untreated rats, but increase the size of the pupil from 1/2 to 4 mm. or more in the morphinized animals.
In another series of experiments, one drop of a 0.002% solution of atropine sulphate was instilled into the conjunctival sac. This installation produced no appreciable change in the normal pupil, but a 60% dilatation in the morphine-treated rats.
Since it is known that morphine causes a secretion of adrenalin from the adrenal gland, it was supposed that this exaggeration of the action of mydriatics by morphine is due to the adrenalin liberated into the blood stream and thus represents a case of additive effects. However, complete adrenalectomies carried out in 25 rats do not support this contention. Adrenalectomized rats under the influence of morphine are just about as sensitive to mydriatics as unoperated controls.
The depression of rats by chloral hydrate or paraldehyde does not enhance the mydriatic effects of adrenalin, cocaine, ephedrine or atropine.
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