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 stress-induced changes in blood pressure, body weight, and [³H]cytisine binding to brain nicotinic receptors were examined in rats and were compared with 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 [³H]cytisine binding sites in cerebral cortex and midbrain. Chronic treatment with (+)- or (-)-nicotine inhibited the stress-induced 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 maximum number of [³H]cytisine binding sites (B(max)) of brain stem, cerebral cortex, and hippocampus. The B(max) in midbrain was also increased by (+)-nicotine 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 central nervous system in rats, which are slightly different between the isomers. Copyright (C) 1999 Elsevier Science Inc.