| Abstract: | Transcortical dialysis was employed to investigate the effects of systemic nicotine (3.6 μmol/kg, sc) administration on cortical extracellular levels of acetylcholine (ACh), norepinephrine (NE), dopamine (DA), and serotonin (5-HT). Systemic administration of [–]-nicotine produced a 106% increase of cortical ACh release over basal levels that persisted for approximately 2 h. Concurrently, NE levels were increased 86% over basal values for 60 min. The effects appear to be stereoselective, as systemic injections of [+]-nicotine significantly increased cortical ACh levels only 48% over basal levels for 30 min, and NE levels in the dialysate only 43% over control levels for 60 min. No significant changes of basal dopamine (DA) or serotonin (5-HT) levels were observed, although DA did appear to increase in response to systemic nicotine. In addition, striatal total endogenous ACh increased significantly over control levels 15 min after [–]-nicotine administration (3.6 μmol/kg, sc), and then significantly declined after 3 h, suggesting that nicotine may influence synthesis as well as release. Analysis of total ACh levels in cortical tissue revealed a similar trend. At the dose utilized in this study, no changes in the cortical electroencephalogram (EEG) were observed. © 1994 Wiley-Liss, Inc. |
