Nicotine-induced regional changes in brain noradrenaline and dopamine turnover in rats

Using high performance liquid chromatography with electrochemical detection, the levels of 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylalanine (DOPA) were determined in various brain regions of the rat 1 h after nicotine administration. Nicotine (1 mg/kg, s.c.) produced an increase in MHPG concentrations in the occipital cortex, hippocampus, striatum, hypothalamus, thalamus, midbrain, pons/medulla and cerebellum. This alkaloid at the same dose also caused an increase in DOPAC concentrations in the hypothalamus, thalamus and pons/medulla. The nicotine-induced increase in MHPG and DOPAC concentrations in the brain regions was inhibited by pretreatment with mecamylamine (5 mg/kg, i.p.) but not by hexamethonium (10 mg/kg, i.p.). Nicotine (1 mg/kg, s.c.) produced an increase in DOPA concentrations under DOPA decarboxylase inhibition with NSD-1015 (200 mg/kg, i.p.) in the hypothalamus, thalamus and pons/medulla. These results indicate that nicotine can increase the turnover of noradrenaline and dopamine in various brain regions of the rat and this effect is mediated via activation of central nicotinic receptors.