Abstract
The effect of bretylium on the degeneration mydriasis and the intraocular pressure decrease after superior cervical ganglionectomy was studied in conscious rabbits. The contralateral eye was decentralized. Two injections of bretylium, 10 mg. per kilogram, given prior to the degeneration mydriasis (at the time of the operation and 8 hours later) delayed mydriasis for about 3.0 to 5.5 hours. The intraocular pressure decrease was delayed for 9 hours. The duration of the delayed mydriasis was larger than in the untreated animals. The duration of the pressure effect did not change significantly. The magnitude of the phenomena was not markedly affected by the drug. Possible explanations for the time lag which exists between the degeneration mydriasis curve and the pressure decrease curve are discussed. Bretylium, given during the degeneration mydriasis, caused an early strong dilatation of the denervated pupil, while the decentralized pupil showed a iveak response. There was a considerable early pressure decrease in both eyes, significantly larger in the denervated eye. The mydriasis gradually disappeared and reappeared as a second wave about 7 hours after the injection of the drug. The second wave of pressure decrease started about 12 to 15 hours after the injection. The magnitude of the second wave of the mydriasis was similar to that in the untreated group. The second wave of the intraoclar pressure decrease was somewhat smaller.