THE DEGENERATION CONTRACTION OF THE NICTITATING MEMBRANE IN THE UNANESTHETIZED CAT

¹ Department of Pharmacology, Harvard Medical School, Boston, Massachusetts

The nictating membrane of the unnanesthetized cat relaxes immediately after denervation or decentralization. Approximately 22 hr after the operation, the denervated nictitating membrane of the quiescent, unanesthetized cat contracted spontaneously for 10 to 14 hr. This phenomenon was not observed on the decentralized nictitating membrane. The term "degeneration contraction" is proposed because the contraction appears to be due to the degeneration of the adrenergic nerve endings in the nictitating membrane. The following findings support this view: 1) the degeneration contraction was interrupted by the administration of phenotolamine; 2) pretreatment with either phenoxybenzamine or dibenamine or with reserpine prevented the appearance of the degeneration contraction. Previous chronic decentralization significantly hastened the appearance of degeneration contraction, and significantly prolonged its duration. Pretreatment with [2(2,6-dimethylphenoxy)-propyl]trimethylammonium chloride monohydrate (-TM 10) delayed the appearance of the degeneration contraction, but did not prevent it. It is concluded that the degeneration contraction is due to the leakage of norepinephrine from the degenerating nerve endings of the denervated nictitating membrane.