Prenatal Nicotine Exposure Alters the Response to Nicotine Administration in Adolescence: Effects on Cholinergic Systems During Exposure and Withdrawal

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Abstract
Maternal smoking during pregnancy increases the likelihood that the offspring will become smokers in adolescence. In the current study, we evaluated effects of prenatal and adolescent nicotine exposure in rats to assess whether there is a biological basis for this relationship. Pregnant rats were given nicotine or vehicle throughout pregnancy and the offspring then again received nicotine or vehicle during adolescence (postnatal days PN30-47.5), using a regimen (6 mg/kg/day by subcutaneous infusion) that produces plasma nicotine levels similar to those in smokers. Evaluations were made in the cerebral cortex and midbrain during adolescent nicotine administration (PN45) and for up to 1 month after the end of treatment. We assessed the magnitude and persistence of nicotinic acetylcholine receptor (nAChR) upregulation; in addition, we evaluated cholinergic synaptic activity by comparing the effects on choline acetyltransferase (ChAT), a constitutive marker for cholinergic nerve terminals, with those on hemicholinium-3 (HC-3) binding to the presynaptic choline transporter, which is regulated by nerve impulse activity. Prenatal nicotine exposure had only minor effects on nAChRs but produced persistent cholinergic hypoactivity (reduced HC-3 binding relative to ChAT) throughout adolescence and into adulthood (PN75). Adolescent nicotine exposure evoked robust nAChR upregulation and also suppressed cholinergic activity. Prenatal nicotine exposure reduced the upregulation of nAChRs evoked by adolescent nicotine but worsened the cholinergic hypoactivity during withdrawal. Our results indicate that prenatal nicotine exposure alters the subsequent response to nicotine in adolescence, effects that may contribute to the association between maternal smoking during pregnancy and subsequent adolescent smoking in the offspring.

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