Motor responses of autoimmune NZB/B1NJ and C57BL/6Nnia mice to arecoline and nicotine.

In 11-13 month C57BL/6Nnia mice, arecoline produced a dose-dependent decrease in motor activity at doses of 0.64-2.5 mg/kg, whereas at doses of 5.0-20.0 mg/kg arecoline produced a dose-dependent increase in motor activity. In marked contrast, age-matched NZB/B1NJ (New Zealand Black) mice failed to exhibit the first phase of the response, but showed a greater dose-dependent increase in motor activity following the doses of 10 and 20 mg/kg. Nicotine, 0.64-2.5 mg/kg, produced a dose-dependent decrease in motor activity in both strains. The effects of arecoline and nicotine were antagonized by scopolamine (2.5 mg/kg) and mecamylamine (1.0 mg/kg), respectively. These findings suggest that muscarinic neurotransmission may be altered in NZB/B1NJ mice, which produce brain-reactive autoantibodies, exhibit learning/memory dysfunctions, and also exhibit a loss of neurons staining positive for choline acetyltransferase.