Effect of Complete Maternal and Littermate Deprivation on Morphine-Induced Fos-Immunoreactivity in the Adult Male Rat Brain

Abstract

Previous research has demonstrated that rats reared in isolation from their dam and littermates show altered behavioral responsiveness to both natural and drug-mediated rewards. This study examined the effects of complete maternal deprivation through the use of artificial rearing on neural activation after acute morphine exposure in adulthood. Male rats were either artificially reared (AR) or maternally reared (MR) from postnatal day 5 to 21. In adulthood (4 mo old), rats received a single injection of morphine sulfate (10 mg/kg) or equivolume saline 2 h before perfusion and brain extraction. Neural activation was quantified using Fos immunohistochemistry. Analyses of several brain regions revealed a consistent pattern of differences between AR and MR rats. Specifically, relative to MR rats, AR rats showed significantly greater morphine-induced Fosimmunoreactivity in brain regions associated with the mesocorticolimbic "reward" pathway. These results support the hypothesis that functional activity in reward neurocircuitry can be altered by early life experience. (Pediatr Res 67: 263-267, 2010)

Morphine exposure induces age‐dependent alterations in pentylenetetrazole‐induced epileptic behaviors in prepubertal rats

“…Pups in the morphine group received morphine subcutaneously (SC) on the back above the tail with additive doses (3,6,9,12,15,18, and 21 mg/kg) every day between 11:00 and 12:00 hr from P8 to P14. These doses were chosen because previous studies reported similar doses (Jones et al, 2002;Rana, Mallet, Robertson, & Wainwright, 2010). Each day, the injected dose of morphine was increased by 3 mg/kg.…”