BEHAVIORAL AND HORMONAL EFFECTS OF CHRONIC RESTRAINT STRESS IN ADOLESCENT AND ADULT RATS
Hansen C, Virgolini MB, De Giovanni L, Miranda-Morales RS, Willie-Billie A, Acevedo MB, Pautassi RM. Instituto de Investigación Médica M. y M. Ferreyra (INIMEC ? CONICET-UNC), Instituto de Farmacología Experimental de Córdoba (IFEC-CONICET), Córdoba, Argentina; Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina. Laboratorio de Análisis Clínicos Especializados (LACE), Córdoba, Argentina.
Aims:, We have previously observed that 5 days of restraint stress enhance alcohol (i.e., ethanol) intake in adolescent but not in adult rats. It is thus important to analyze age-related differences in response to restraint stress (RS), which may explain the higher predisposition to stress-induced ethanol drinking in adolescents. Methods:, This experiment measured anxiety response in a light-dark box (LDB) test as well as stress-induced corticosterone (CORT) levels in adolescent and adult Wistar rats that had been exposed to immobilization (restraint) stress (120 min of restraint a day, for 5 days; or non-stressed). Immediately after the LDB test, animals were exposed for 5 min to inescapable stress (confinement in the white section of the LDB with illumination of 1200 lux). Blood samples were collected 90 minutes before LDB test, and immediately after termination of the inescapable stress. Results:, Chronic RS affected later behavioral response to acute stress (i.e., immobilization was increased) in adults (t22 = -2.98, p < 0.01) but not in adolescents; whereas adolescent, but not adult, rats exhibit lower baseline levels of two anxiety-like responses in the LDB as a function of prior RS. Stressed adolescents spent more time in the bright compartment [t22 = 2.09, p<0.05] and moved significantly more often between compartments [t22 = 2.31, p<0.05] than control, non-stressed adolescents Corticosterone release was significantly enhanced by acute stress exposure (F1,21 = 60.20, p <0.001 and F1,21 = 77.86, p <0.001; for adolescent and adults, respectively). This response was fairly similar in both ages and in rats exposed or not to chronic stress, although there was a trend for lower baseline corticosterone scores in adolescents given chronic RS. Conclusions:, The results are suggestive of stress-induced increases in impulsivity or inadequate risk assessment in adolescents, which may put them at risk for alcohol and drug initiation.
Keywords: ethanol, adolescent rat, anxiety, corticosterone
