Individual variability of dopamine release from nucleus accumbens induced by nicotine

Effects of subcutaneous administration of vehicle, amphetamine (1 mg/kg) or nicotine (0.4 mg/kg, injected twice, 90 min apart) on extracellular dopami ne (DA) concentration in the nucleus accumbens (ACC) and ventral tegmental area (VTA) of the Sprague-Dawley rat were studied using microdialysis. Expe riments were conducted at least 10 days following implantation of guide can nulae, and at least 2 h following insertion of microdialysis probes into th e guides on the morning of each experiment. Probes were perfused at 2.5 mu l/min and several fractions were collected every 10 min before and after th e two test injections. Samples were analyzed by high-performance liquid chr omatography with electrochemical detection for the major neurotransmitters and their metabolites. Significant DA release following nicotine administra tion was observed in ACC but not in VTA, By classifying ACC DA responses of individual rats, three major subgroups were identified which exhibited mor e robust responses. Nicotine appeared to be acting as a modulator of ACC DA , increasing DA output if baseline was <5 nM, but slowing release when the baseline exceeded 5 nM, These data are consistent with previous reports of modulation of arousal level by nicotine via DA. (C) 2000 Elsevier Science I nc.