The Effect of early environmental manipulation on locomotor sensitivity and methamphetamine condition place preference reward

Early life stress has drastic effects on neurological development, affecting health and well-being later in life. Instances of child abuse and neglect are associated with higher rates of depression, risk taking behavior, and an increased risk of drug abuse later in life (Chapman,D.P. 2004; Dube,S.R. 2003). This study used repeated neonatal separation of rat pups as a model of early life stress. Rat pups were either handled and weighed as controls or separated for 180 minutes per day during postnatal days 2-8. In adulthood, rats were tested for methamphetamine conditioned place preference reward and methamphetamine induced locomotor activity. Tissue samples were collected and mRNA was quantified from the following brain regions: prefrontal cortex (norepinephrine transporter), nucleus accumbens (dopamine transporter), and ventral midbrain (cocaine-amphetamine regulated transcript). Results indicated rats given methamphetamine formed a conditioned place preference, but there was no effect of early separation or sex. Separated males showed heightened methamphetamine-induced locomotor activity, but there was no effect of early separation for females. Overall females were more active than males in response to both saline and methamphetamine. This suggests early neonatal separation may differently affect methamphetamine-induced locomotor activity and methamphetamine reward. Additionally, these effects on locomotor activity are likely sex-dependent