Effects of gestational nicotine exposure on hippocampal morphology

Morphology of the dentate gyrus and Ammon's horn of the hippocampus was observed postnatally in Wistar rats exposed to prenatal nicotine. Pregnant Wistar rats were injected with nicotine (2.5 mg/kg/ day) from gestational day (GD) 6 to term and pups were delivered at term normally. The brains of nicotine-exposed pups at postnatal day (PND) 40 were dissected and processed for araldite embedding. Semithin (0.5 microm) toluidine blue-stained sections of the dentate gyrus, CA3, and CA1 regions of the hippocampus were studied for morphological details. Morphometric analysis showed a significant reduction in the neuronal area of nicotine-exposed brains in all three regions studied. Distal dendritic arbor was significantly less and spine density was more in the granule cells, terminal and basal dendrites of the pyramidal neurons of CA3 and CA1 regions of the hippocampus in the experimental group. CA3 pyramidal neurons showed significantly less apical dendritic thorny excrescence after gestational nicotine exposure. Ultrastructurally the granule cells and the pyramidal neurons of the CA3 and CA1 regions showed increase in free ribosomes and dilatation of rough endoplasmic reticulum (RER) and Golgi apparatus cisternae in the nicotine-treated group. The morphological changes in the hippocampus following prenatal nicotine exposure, as observed in the present study, may contribute to the behavioural abnormalities.