Early social isolation, but not maternal separation, affects behavioral sensitization to amphetamine in male and female adult rats

Early life stressful manipulations, such as maternal separation (MS) or soc ial isolation (SI), can influence the neurobiological development of rats a nd alter the response of adult animals to drugs of abuse. The present study , examined the acute and sensitized behavioral responses (locomotor activit y (LMA) and stereotypy) induced by amphetamine after MS or SI in male and f emale rats. In addition, the hypothesis that the combination of SI and MS c ould lead to additional effects on the behavioral response to amphetamine w as tested. After the repetitive, intermittent administration of 1.5 mg/kg D -amphetamine over five consecutive days, the behavioral expression of sensi tization to a challenge injection was assessed following a 2-day withdrawal period. In both sexes, MS and SI did not alter the acute locomotor activat ing effects of amphetamine as measured in the open-field environment after the first administration of the drug. Whereas SI altered the expression of sensitization to amphetamine in both sexes, MS did not affect it. Finally, in none of the behavioral variables measured did MS and SI interact to furt her modify the behavioral profile of the animals. The present results sugge st that a postweaning manipulation of the environment (SI) is more effectiv e than a preweaning manipulation (MS) in modifying the expression of sensit ization to amphetamine. (C) 2001 Elsevier Science Inc. All rights reserved.