A single cocaine exposure disrupts actin dynamics in the cortico-accumbal pathway of adolescent rats: modulation by a second cocaine injection.

Abstract

Among the changes caused by repeated exposure to drugs of abuse, structural rearrangements play a critical role, setting the stage for maladaptive responses to environmental challenges and sustaining drug-taking and drug-seeking behaviors. Given that adolescents are more vulnerable to drug abuse than adults and based on our recent data showing that a single exposure to cocaine during adolescence is sufficient to change the adolescent brain, we decided to investigate whether acute cocaine exposure may alter actin remodeling in reward-related brain regions. Accordingly, we decided to evaluate if F-actin/G-actin ratio was altered by a single injection of cocaine (20mg/kg) at postnatal day 35. We also evaluated whether the first administration of cocaine influences such a ratio in response to a second injection (10mg/kg) provided 24h or 7days later. Within the medial prefrontal cortex, a single cocaine injection increases the F-actin/G-actin ratio. This effect lasts 1week, and it is not affected by the second injection of cocaine, indicating a persistent effect of the first exposure. In the nucleus accumbens, cocaine reduces the F-actin/G-actin ratio 24h later. Seven days later, instead, such a ratio is markedly increased: notably, the additional exposure to the psychostimulant normalizes the F-actin/G-actin ratio. These results suggest that a single cocaine injection during adolescence causes possible changes in actin dynamics and influences the response to a second challenge of the psychostimulant, indicating that early cocaine priming might affect mechanisms regulating synaptic structural plasticity in specific brain regions.