Prior morphine facilitates the occurrence of immobility and anhedonia following stress

ALEJANDRA ZURITA,; MOLINA VICTOR ALEJANDRO

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1998 vol. 65 p. 833 - 833

he role of the activation of the opiate system either induced by a 120-min restraint session or by a single morphine administration (10 mg/kg, i.p.) on the behaviors performed in a subsequent forced-swim test has been evaluated. In addition, animals were pretreated with naloxone (2 mg/kg, i.p.) prior to restraint or to morphine. Furthermore, in order to evaluate if this opioid mechanism could participate in the effect of stress on the response to a rewarding stimulus, rats were administered with morphine (10 mg/kg, i.p.) - whether associated or not with prior naloxone (2 mg/kg, i.p.) administration - and subsequently exposed to a 90-min restraint period. Following stress, all rats were submitted to a sucrose (1%) preference test. Both morphine and restraint enhanced the time spent in immobility in the forced-swim test. Both behavioral effects were attenuated by naloxone pretreatment thus suggesting that the increased immobility is probably modulated by the previous activation of an op