Chronic variable stress or chronic morphine facilitates immobility in a forced swim test: Reversal by naloxone

MOLINA VICTOR ALEJANDRO; HEYSER, C.; SPEAR, L.

SPRINGER

Lugar: Berlin; Año: 1994 vol. 114 p. 433 - 433

p class="marginB3" align="justify">The behaviors displayed in a forced swim test were investigated in rats previously exposed to a chronic variable stress treatment or chronic administration of morphine. In addition, to further explore the participation of an endogenous opiate mechanism in these behavioral effects, naloxone was either administered during the chronic treatment (prior to each stress or morphine exposure) or immediately prior to the forced swim test. Animals were submitted daily to a different stressor for 1 week or injected with morphine (10 mg/kg, IP) for 6 days, whereas controls were unmanipulated except for the injection process. On the day following the last stressor, control and stressed animals were administered saline or naloxone (2 mg/kg, IP) 15 min prior to the forced swim test. Morphine treated animals were similarly tested on the third day following the last morphine injection. In a separate group of rats, naloxone (2 mg/kg, IP) was administered daily 10 min