Degeneration mydriasis and hyperemia of the iris after superior cervical ganglionectomy in the rabbit. Evidence for release of more than norepinephrine during degeneration of adrenergic terminals.

Two intraocular phenomena folloiuing sympathetic denervation—degeneration mydriasis and degeneration hyperemia of the iris—were studied in conscious albino rabbits. The superior cervical ganglion was removed on one side (denervation) and the preganglionic sympathetic trunk was cut on the control side. Mydriasis and hyperemia toere judged by comparing the two eyes. Mydriasis started about 14.5 hr. after denervation and hyperemia appeared 3 to 4.5 hr. later. Bretylium caused a markedly longer delay of the hyperemia than of the mydriasis. Neither phenoxybenzamine, phentolamine, chlorpromazine, nor splroperidol prevented the hyperemia, they influenced neither its starting time nor its intensity. Reserpine did not influence starting time but possibly reduced intensity. These drugs eliminated the first 1 to 3 hr. of mydriasis completely, but were only partially active on later stages. Neither propranolol nor butoxamine prevented or affected the hyperemia or the mydriasis. Systemic atropine enlarged the pupils but did not influence the hyperemia. Topical lidocaine neither prevented nor influenced the hyperemia or the mydriasis. Making the eye resistant to irritation hyperemia by repeated trauma failed to prevent the degeneration hyperemia.