Chronic morphine alters calbindin D-28k immunostaining patterns in mouse forebrain.

The influence of chronic morphine treatment on the brain of adult mouse has been studied. Female Swiss mice were daily administered saline or morphine (30 or 60 mg/kg body weight) for a period comprising 7 days before mating, during gestation and until 21 days post-partum. Their brains were then perfusion-fixed and examined for histology and calbindin D-28k protein-immunoreactivity. Histological observations revealed no significant changes in the various brain regions; whereas a reduced number of calbindin-positive cells was encountered in the cingulate and parietal cortices and the lateral septal regions of morphine-treated brains compared with those of controls. The alteration in the expression-patterns of this neuroprotective calcium-binding protein in specific regions of the adult brain might be one of the mechanisms by which the addictive drugs modify the functional aspects of the CNS.