SENSITIVITY OF THE ISOLATED NICTITATING MEMBRANE OF THE CAT TO NOREPINEPHRINE AND ACETYLCHOLINE AFTER VARIOUS PROCEDURES AND AGENTS

¹ Department of Pharmacology, The William S. Merrell Company, Division of Richardson-Merrell Inc., Cincinnati, Ohio

The sensitivity of the isolated medial smooth muscle of the nictitating membrane of the cat to l-norepinephrine (NE) and acetyicholine (ACh) was determined 1) in the presence of cocaine 10^-4 M, 2) 2 to 28 days after denervation, 3) 7 to 28 days after decentralization, 4) after 1 day of treatment with 3 mg/kg of reserpine, 5) after 7 and 14 days treatment with 0.1 mg/kg/day of reserpine, 6) after 7 days treatment with 2 to 5 mg/kg of chiorisondamine twice a day and 7) after 7 days treatment with 10 mg/kg/day of bretylium or -TM-10. Procedures 1, 2 and 7 resulted in supersensitivity of the isolated nictitating membrane to NE but not to ACh. Procedures 3, 4, 5 and 6 did not induce supersensitivity of the isolated nictitating membrane to NE or ACh. Denervation supersensitivity developed rapidly during the 2nd postoperative day and reached its maximum between the 2nd and the 7th postoperative day. Cocaine did not cause additional supersensitivity of the denervated (7 days after denervation) nictitating membrane to norepinephrine. The results show a) that the supersensitivity of the isolated nictitating membrane after the outlined procedures and agents is specific for NE; b) that in contrast to in vivo results procedures 3, 5 and 6 did not induce supersensitivity to NE or ACh when sensitivity was tested in vitro; and c) that the supersensitivity of the isolated nictitating membrane to NE is mainly due to the impairment of uptake of NE.