Mydriasis and intraocular pressure decrease in the conscious rabbit after unilateral superior cervical ganglionectomy.

Hourly measurements of the transient mydriasis and intraocular pressure decrease after right cervical ganglionectomy and left cervical sympathotomy were simultaneously performed in conscious rabbits. The times of onset of these phenomena after the denervation were 14.51 0.21 hr. (n = 8) and 18.71 ± 0.78 hr. (n = 7), respectively. Their duration values were 18.01 ± 0.89 hr. (n = 8) and 18.81 ± 1.02 hr. (n = 4). The magnitudes of the mydriasis and the pressure decrease were 2.78 ± 0.26 and 6.00 ± 0.51 mm. Hg, respectively. The degeneration mydriasis has its peak 2 to 3 hr. later than one coidd expect from published data on the postdenervation transmitter disappearance from the iris. This time lag could be caused by denervation supersensitivity. Degeneration mydriasis is not affected by bilateral adrenalectomy or hexamethonium. A residual mydriasis was found to persist after the degeneration mydriasis had subsided and icas also unaffected by hexamethonium or bilateral adrenalectomy. Probably it is due mainly to the transmitter remaining in the aqueous humor. The pressure decrease was found to occur 4 to 5 hr. later than the mydriasis and 1 to 3 hr. later than the appearance of tritiated norepinephrine in the anterior chamber reported by others.