Hyperactivity in the offspring of nicotine-treated rats: role of the mesolimbic and nigrostriatal dopaminergic pathways.

To evaluate the involvement of the mesolimbic and nigrostriatal dopaminergic systems in hyperactivity in offspring of nicotine-treated dams, timed-pregnant Sprague-Dawley rats were implanted SC on gestational day 4 with osmotic minipumps to receive saline or nicotine (3 or 6 mg/kg/day) for 16 days. Hyperactive and nonhyperactive male offspring of nicotine-treated dams as well as nonhyperactive offspring of saline-treated dams were selected and sacrificed at day 22 postnatally. Discrete brain areas (the nucleus accumbens [NAcc], striatum [STR], frontal cortex [FC], ventral tegmental area [VTA], and substantia nigra [SN]) were microdissected for the evaluation of dopamine (DA) concentration and/or the D2 receptor subtype. Dopamine concentration was decreased in the VTA and STR but was increased in the SN of the hyperactive offspring. The reduction in striatal DA level was associated with a reduction in the number of D2 receptors in that area. The data suggest a role for the VTA and striatal dopaminergic system in offspring hyperactivity.