Effects of subchronic late-gestational nicotine exposure on postpartum maternal behavior in Wistar rats: An exploratory pilot study

Objective This exploratory pilot study evaluated whether subchronic late-gestational oral nicotine exposure alters postpartum maternal behavior in Wistar rats. Methods Twelve pregnant Wistar rats were obtained in three successive intake batches and randomly assigned to experimental or control groups. Control animals received a 2% saccharin solution; experimental animals received nicotine (nominal 200 μg/mL) in 2% saccharin solution ad libitum from gestational day 7 through parturition. The initial concentration of 200 μg/mL produced two maternal deaths and one embryonic reabsorption in the first experimental batch; the solution was diluted approximately 1:3 to ~50 μg/mL for the third experimental batch. Postpartum maternal behavior was scored from 15-min light-phase video samples (three 5-min blocks at 5-s instantaneous sampling) on each of the 14 postpartum days. Dependent variables were daily frequency counts of 19 ethogram behaviors organized into proximal, nest-related, motor, and self-maintenance categories. Primary analyses were 2 × 14 mixed repeated-measures ANOVAs. Fluid consumption, litter parameters, and cohort attrition are also reported. Results Experimental dams reduced solution consumption by approximately 81% relative to their pre-nicotine water baseline, indicating that actual nicotine exposure was substantially below the nominal concentration. Among the three surviving dams per group, proximal maternal behaviors showed no reliable group differences on either parametric or non-parametric tests. The clearest between-group difference was in eating frequency (controls > experimentals; F(1, 4) = 48.96, p = .002, ηp 2 = 0.92). A significant Day × Group interaction was observed for locomotion, concentrated on postpartum days 11–12. Conclusions In this small pilot, subchronic late-gestational nicotine exposure did not produce consistent alterations in core proximal maternal behaviors among surviving dams, but was associated with substantial gestational losses, reduced maternal fluid intake, a qualitative low-pup-birth-weight observation, and a postpartum eating-frequency difference that cannot be unambiguously attributed to nicotine pharmacology. The findings are hypothesis-generating and motivate adequately powered replication with cotinine verification and gravimetric pup-weight measurement.