Kappa blockade does not affect spontaneous or ethanol-induced motor activity in rats exposed to early neonatal stress

MACARENA FERNÁNDEZ; PAUTASSI RM

Concepción

Workshop; First Joint Meeting on Alcohol and other Drugs of Abuse: from molecules to human disorders; 2013

Latin American Society for Biomedical Research on Alcoholism andLatin American Research Network in Drug Abuse

The maternal separation paradigm (Plotsky and Meaney, 1993) is a model of early neonatal stress that can alter responsivity to ethanol?s motivational (appetitive, aversive, and negative reinforcing) effects. These effects play an important role in the modulation of ethanol-seeking and intake. The kappa opioid system regulates the response to ethanol and also to chronic and acute stress (Land et al, 2009). Previous experiments indicated that early neonatal stress enhances sensitivity to the motor activating effects of ethanol, lessens sensitivity to the motor depressing effects of the drug and increases overall level of activity. The aim of the present work was to assess if these alterations can be reverted by blockade of kappa receptors. Infant rats were exposed to 4 daily hours of maternal separation, from postnatal day 1 to 14, and then were given the kappa blocker nor-BNI (0.0, 1.0, 5.0 o 10 mg/kg, ip). Twenty-four hours later they were assessed for baseline and ethanol-induced motor activity in an inescapable environment (dose: 2.5 g/kg). The analysis indicated significant and independent main effects of nor-BNI, ethanol treatment and maternal separation. Ethanol and maternal separation increased motor activity, and the highest nor-BNI dose suppressed motor activity. Our hypothesis of nor-BNI blocking ethanol- or novelty-induced motor activity, however, was not corroborated. Spontaneous or ethanol-induced motor activity was not affected by the kappa blocker, neither in animals given chronic maternal separation nor in those reared under normal housing conditions.