Effects of chronic treatment with (+)-nicotine on the stress-induced hypertension and downregulation of central nicotinic receptors in rats - Comparative study with (-)-nicotine

The effects of chronic treatment with (+)-nicotine on the immobilization st ress-induced changes in blood pressure, body weight, and [H-3]cytisine bind ing to brain nicotinic receptors were examined in rats and were compared wi th those of (-)-nicotine. Immobilization stress (2 hr/day(-1), for 2 weeks) induced a moderate elevation of blood pressure, loss of body weight gain, and downregulation of [H-3]cytisine binding sites in cerebral cortex and mi dbrain. Chronic treatment with (+)- or (-)-nicotine inhibited the stress-in duced hypertension but did not suppress the inhibition of body weight gain by stress. Body weight before stress load was also reduced by (-)-nicotine but not (+)-nicotine treatment. Treatment with each isomer increased the ma ximum number of [H-3]cytisine binding sites (B-max) of brain stem, cerebral cortex, and hippocampus. The B-max in midbrain was also increased by (+)-n icotine but not by (-)-nicotine. Stress-induced downregulation in cerebral cortex was inhibited by both isomers. These results suggest that (+)- and ( -)-nicotine cause various effects, including anti-stress effect, on the cen tral nervous system in rats, which are slightly different between the isome rs. (C) 1999 Elsevier Science Inc. All rights reserved.