Risk-taking, locomotor activity and dopamine levels in the nucleus accumbens and medial prefrontal cortex in male rats treated prenatally with alcohol.

Background: Prenatal alcohol exposure (PA) restricted to days 8-20 of rat gestation reduces the activity of the dopaminergic neurons (DA) in the ventral tegmental area (VTA). Hyperactivity and impulsivity have been observed under this treatment; however, it is unknown whether DA levels are affected. Decision-making in risk situations, meanwhile, has been associated with impulsive behavior, but because studies of this phenomenon in animal models are limited, we do not yet know whether PA has any effect. The present study investigated the effects of PA on risk-taking behavior and locomotor activity in pre-pubertal male rats. In addition, DA levels in the nucleus accumbens (NAcc) and medial prefrontal cortex (mPFC) in response to methylphenidate (MP) were assessed.

Methods: Dams were treated with either two daily 3.0-g/kg doses of alcohol or an isocaloric solution, from days 8-20 of gestation. Locomotor activity and risk-taking in pre-pubertal male rats after PA, and DA levels in the NAcc and mPFC after a single dose of MP (5mg/kg), were analyzed.

Results: Hyperactivity and increased risk-taking behavior were observed in the rats treated prenatally with alcohol compared to controls. Methylphenidate increased DA levels in the NAcc regardless of prenatal treatment, but significantly higher DA levels were found in the PA group regardless of postnatal treatment with saline or MP.

Conclusion: The presence of hyperactivity and increased risk-taking behavior after prenatal alcohol treatment is supported. Results suggest that higher DA levels in the rats with PA could be due to a down-regulation of postsynaptic receptors, the desensitization of presynaptic receptors, or a compensatory over-activity of DA neurons in the VTA.