Anticholinergic sensitivity following chronic nicotine administration as measured by radial-arm maze performance in rats.
Chronic nicotine administration in rats has been previously found to improve choice accuracy performance of rats in the radial-arm maze. A nicotine-induced choice accuracy improvement was also seen in the current study. Rats were trained to asymptotic levels of choice accuracy performance on a working memory paradigm in an 8-arm radial maze. During and after 3 weeks of chronic nicotine treatment, rats were tested for sensitivity to acute doses of the nicotinic and muscarinic receptor antagonists, mecamylamine and scopolamine. During the first week of administration, nicotine-treated rats were supersensitive to the sedation caused by mecamylamine. This suggests that nicotine may not have been acting as a simple nicotinic agonist, since in this case, the opposite effect, an attenuated effect of mecamylamine in the nicotine-treated group, would have been expected. Three to 4 weeks after withdrawal from chronic nicotine administration, the treated rats were more sensitive to the choice accuracy deficits caused by the muscarinic blocker scopolamine (0.16 mg/kg) and the nicotinic blocker mecamylamine (10 mg/kg). This supersensitivity may have been due to a lasting change caused by chronic nicotine in the cholinergic bases of memory function.
Levin
E.D.
ED
Nicotine Research Laboratory, VA Medical Center and Department of Psychiatry, Duke University, Durham, NC, USA Correspondence to E.D. Levin, Nicotine Research Laboratory-151, VA Medical Center, 508 Fulton St., Durham, NC 27705, USA.
Rose
J.E.
JE