Effect of acute nicotine administration on striatal dopamine output and metabolism in rats kept at different ambient temperatures

The effect of ambient temperature on the nicotine‐induced (0.3, 0.5 or 0.8 mg kg −1 s.c.) changes of the striatal concentrations of dopamine (DA) and its metabolites 3,4‐dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) was studied in freely‐moving rats by in vivo microdialysis. At the ambient temperature of 30–33°C, but not at 20–23°C, nicotine doses of 0.5 ( P <0.01) and 0.8 mg kg −1 ( P <0.05) significantly increased the extracellular DA concentration. The nicotine doses of 0.5 and 0.8 mg kg −1 increased the DA metabolite levels similarly at both ambient temperatures studied ( P 0.0001), but the dose of 0.3 mg kg −1 only at 30–33°C (DOPAC: P <0.05; HVA: P <0.01). At 30–33°C, dihydro‐β‐erythroidine (DHβE 2.8 mg kg −1 i.p.) blocked the nicotine‐induced (0.5 or 0.8 mg kg −1 ) increases of extracellular DA concentration but only tended to antagonize the increases of DA metabolites. Mecamylamine (5.0 mg kg −1 i.p.) blocked the increase of DA output induced by 0.5 mg kg −1 but not that induced by 0.8 mg kg −1 of nicotine and fully prevented the nicotine‐induced elevations of DOPAC and HVA. Elevation of ambient temperature did not affect the cerebral concentration of nicotine or the nicotine‐induced elevation of serum corticosteroids. Also, the rectal temperatures of rats given nicotine at either ambient temperature did not significantly change. Our results show that the nicotine‐induced output of striatal DA is enhanced at high ambient temperature. Further, our findings suggest that the nicotinic cholinoceptors mediating the effects of nicotine on striatal DA release are different from those mediating nicotine's effects on DA metabolism.British Journal of Pharmacology (2000) 130 , 1147–1155; doi: 10.1038/sj.bjp.0703402