Abstract: To investigate potential mechanism of nicotine dependence, online microdialysis sampling coupled with electrochemical detector was applied to study the contents of dopamine (DA), 3,4-dihydroxyphenyl acetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT) and 5-hydroxylindole acetic acid (5-HIAA) in the nucleus accumbens of alive rats exposed to nicotine.Dialysates were collected every 15 min at a flow rate of 1.5 <i<μ</i<L/min and separated immediately under the gradient elution condition.After nicotine administration (1.0 mg/kg, s.c.), the release of DA and 5-HT increased significantly, and the metabolites DOPAC, HVA and 5-HIAA were raised continuously.In nicotine-dependence rats, 3.0 mg/kg nicotine injection could stimulate the equivalent release of DA, 5-HT and their metabolites.The results provide an alternative approach and data reference for studying the mechanism of nicotine dependence.