The effects of acute nicotine on the body temperature and striatal dopamine metabolism of mice during chronic nicotine infusion

The effects of acute nicotine administration on body temperature and striat al dopamine metabolism of mice during chronic subcutaneous nicotine infusio n were investigated. On the 7th day of nicotine infusion the hypothermic ef fect of 1 mg/kg nicotine s.c. but not that of 2 mg/kg was weakened suggesti ng that tolerance developing to nicotine's hypothermic effect during chroni c nicotine can be overcome by increasing the dose of nicotine. In saline-in fused control mice 1 mg/kg nicotine increased striatal 3,4-dihydroxyphenyla cetic acid (DOPAC) but not homovanillic acid (HVA) concentration whereas 2 mg/kg increased both DOPAC and HVA. On the 7th day of nicotine infusion DOP AC and HVA concentrations were similar to control; and acute nicotine did n ot increase them suggesting that nicotinic acetylcholine receptors (nAChRs) regulating striatal dopamine metabolism were desensitized. The results sug gest that the nAChRs mediating nicotine's effects on thermoregulation and b rain dopamine metabolism differ. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.