The nicotine-induced changes in striatal dopamine metabolism of mice depend on body temperature.

The effects of single and 4 times repeated doses of nicotine on the striatal concentrations of dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were studied in mice in relation to the nicotine-induced decrease of the body temperature. The single doses of nicotine (0.3, 1, 3 or 10 mg/kg s.c.) increased the DOPAC and HVA concentrations in mouse striatum depending on the dose and the rectal temperature of the mice. The elevations lasted longer and were induced by smaller doses when the decrease of the rectal temperature was prevented by increasing the ambient temperature. At a high ambient temperature (32-34 degrees C) the repeated nicotine doses (4 X 1, 3 or 10 mg/kg s.c.) elevated the striatal DOPAC and HVA concentration. When, however, the hypothermia was not prevented, the repeated doses decreased the striatal HVA concentration and induced less elevation of the striatal DOPAC concentration. It is suggested that nicotine acts on the cholinoceptive receptors regulating striatal dopamine release as it acts on the nicotinic receptors in the autonomic ganglia or in the end-plate regions of the skeletal muscle. Initial activation of the receptors could be followed by a block, which is enhanced by hypothermia.