Heightened cocaine-induced locomotor activity in adolescent compared to adult female rats

Abstract

Initiation and experimentation with illicit drugs often occurs in adolescence. Evidence suggests that adolescent rats are more sensitive to some of the effects of drugs of abuse than adult rats. The present study investigated whether adolescent and adult female Sprague Dawley rats differ in cocaine-induced locomotor activity. Animals were placed in the test environment for 30 minutes, and then administered an intraperitoneal (IP) injection of either cocaine (20mg/kg) or saline (0.9%). Both adult and adolescent animals showed significant increases in locomotor activity as a result of cocaine administration compared to saline controls. Interestingly, cocaine induced significantly more locomotor activity in the adolescent females compared to the adults, demonstrating that cocaine acts differently in developing animals.

Figure 1. Locomotor differences between adolescent and adult female rats

Animals were placed in the test environment for 20 minutes before receiving saline IP (time point 0) followed by 20 mg/kg cocaine IP 10 minutes later (time point 10). Locomotor activity was measured by TDM (cm). PND 35 cocaine animals and PND 60 cocaine animals both show a significant increase in TDM compared to age-matched, saline-matched controls (p < 0.05). PND 35 animals showed an enhanced locomotor response compared to PND 60 (p < 0.05) (indicated by *)