Neonatal nicotine exposure alters hippocampal EEG and event-related potentials (ERPs) in rats

A consensus is farming that nicotine can damage the developing rat central nervous system. However, few studies have assessed the electrophysiological effects of neonatal nicotine exposure in rodents in brain regions known to be sensitive to the teratogenic properties of nicotine. In a previous stud y it was reported that 1.0 and 4.0 mg/kg/day nicotine exposure from postnat al days 4-9, a developmental period corresponding to human third trimester exposure, significantly altered hippocampal event-related potentials (ERPs) but did not effect cortical ERPs, cortical EEG, or hippocampal EEG. Becaus e alterations in behavior and cortical/hippocampal neurochemistry and morph ology have been reported following nicotine exposure, the present study use d a higher dose of nicotine during the postnatal period (6.0 mg/kg/day) det ermine if functional changes in the EEG of these regions might contribute t o behavioral changes that have been observed. Male Sprague-Dawley rats were exposed to 6.0 mg/kg/day nicotine via gastric infusion using an artificial rearing: "pup-in-the-cup", technique for 6 consecutive days (postnatal day s 4-9). At adulthood, EEG and auditory ERPs were recorded from the cortex a nd hippocampus. There were no significant differences in EEG or ERPs record ed from the cortex between nicotine-treated and control subjects. Examinati on of the hippocampal EEG revealed significantly decreased power in the 1-2 -Hz frequency band of nicotine-treated rats. In addition, there was a signi ficantly attenuated P300 ERP response to a noise tone in the nicotine treat ed rats compared to controls. These data indicate that neonatal nicotine ex posure alters functional activity in the hippocampus of adult rats. These e ffects are likely to be the result of synaptic disorganization in the hippo campus, and indicate that neonatal nicotine exposure exerts teratogenic eff ects on the developing central nervous system, particularly the hippocampus , which persist into adulthood. (C) 2000 Elsevier Science Inc.