CORTICOSTERONE EFFECTS ON RAT CALRETININ MESSENGER-RNA IN DISCRETE BRAIN NUCLEI AND THE TESTES

Calretinin is an EF-hand calcium binding protein found predominantly i n discrete sets of neurons in the central system, and in the sex hormo ne producing cells of the gonads. Calretinin mRNA levels were measured in discrete brain areas from vehicle and corticosterone treated rats (subcutaneous injections of 0, 0.1, 1, or 10 mg, 7 days) using a micro punch ribonuclease protection assay. Treatment with high dose corticos terone (10 mg) caused a 93% decrease in calretinin mRNA levels in the hypothalamic paraventricular nucleus compared to controls. Two other b rain regions, the medial amygdaloid nucleus and the nucleus reuniens, demonstrated an approximately 40% decrease in calretinin mRNA followin g high dose corticosterone. In separate experiments, adrenalectomy and diurnal corticosterone variations had no effect on calretinin mRNA in the brain areas examined. In the testes, corticosterone treatment dec reased calretinin protein in a dose dependent fashion (to 81%, 68%, an d 39% of controls at doses of 10, 1, and 0.1 mg/day, respectively). Lo w dose corticosterone treatments decreased testicular but not neuronal calretinin mRNA, whereas high dose corticosterone reduced calretinin mRNA in testes and several discrete brain areas. This suggests that co rticosterone's effects on brain calretinin may be due to its pathologi cal effects, e.g. energy depletion of brain cells or interference with the normal support functions of glia.