Aim: The present
study determined the extent to which individual differences in responses to the psychostimulating effect of nicotine during
adolescence predict similar individual differences during adulthood in
rats. We also examined the possible
long-term effects of adolescent nicotine exposure on adult prepulse inhibition (PPI) of the acoustic startle response, a measure of sensorimotor gating ability.
Methods: During the
adolescent phase, rats were administered saline, 0.10, 0.40, or 0.60 mg/kg
nicotine via subcutaneous injections for 8 days, and motor activity was
measured daily. During the adult
phase, these rats were treated with the same nicotine dose as in adolescence
for 8 additional days. The
adolescent saline rats (now adults) were subdivided into four groups and
administered saline, 0.10, 0.40, or 0.60 mg/kg nicotine, respectively. PPI was assessed 12 days after the last
nicotine treatment.
Results: During
both phases, nicotine increased motor activity across test days in a
dose-dependent manner. Motor
activity of rats treated with nicotine during adolescence was positively
correlated with the activity recorded from the same rats during adulthood. In both phases, there were profound
individual differences in the responses to the nicotine treatments. In addition, adolescent rats treated
with nicotine did not show decreased motor response to the initial exposure to
nicotine. Finally, adolescent
exposure to nicotine at 0.4 mg/kg, but not adulthood exposure to the same dose
of nicotine, produced a robust disruption of PPI, with individual rats showing
different degrees of PPI disruption.
Conclusion: These
findings suggest that adolescent rats have increased sensitivity to the psychostimulating effect and decreased sensitivity to the
aversive effect of nicotine. Also,
nicotine exposure during adolescence may have long-term detrimental effects on sensorimotor gating ability.
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