Responsiveness to methamphetamine in adulthood is altered by prenatal exposure in rats

Methamphetamine (MA) is a drug causing potent psychomotor activation. The aim of the present study was: (1) to assess the effect of prenatal and acute MA administration on behavior in adult male rats and (2) to find out if the prenatal exposure to MA increases sensitivity to acute MA application in adulthood. Behavior of adult male rats prenatally exposed to MA (5 mg/kg) or saline was tested in Open field (OF) and Elevated plus maze (EPM). Subcutaneously administered MA (1 mg/kg) or saline were used as challenge in adulthood, 30 min prior to testing. Our results showed that prenatal MA did not have an effect on baseline behavior in either of the tests. By contrast, acute MA increased overall psychomotor activity by increasing locomotion and exploratory behavior and decreasing comforting behavior. Moreover, adult rats prenatally exposed to MA exhibited increased sniffing and decreased rearing after acute MA dose in adulthood relative to prenatally saline-exposed rats. In addition, while acute MA application decreased anxiety in rats prenatally exposed to MA, rats prenatally exposed to saline were less sensitive to the anxiolytic effects of MA. Our results indicate that changes caused by prenatal exposure to psychostimulants may become apparent as different reactivity to drugs of abuse when an individual encounters them later in life. In addition, we found that the anxiolytic effect of acute MA (1 mg/kg) probably depends also on the reactivity to stress and the activity of hypothalamo-pituitary-adrenal axis. (C) 2009 Elsevier Inc. All rights reserved.