Expression of vasopressin mRNA in extrahypothalamic nuclei of the homozygous brattleboro rat is not modulated by testosterone

Previous studies from this and other laboratories have shown that levels of vasopressin (VP) mRNA are reduced in both hypothalamic magnocellular and extrahypothalamic nuclei of the homozygous Brattleboro rat (HOM) when compared to the normal Long-Evans (LE) and heterozygous Brattleboro rats (HET). Since extrahypothalamic VP gene expression is dependent on testosterone (T), we measured plasma T in HOM, HET and LE rats. The plasma T level of the intact HOM rat was not significantly different from intact LE or HET rats. Manipulation of circulating gonadal steroids by castration and T replacement was found to regulate the expression of VP mRNA in the bed nucleus of the stria terminalis and medial amygdala of LE and HET rats, but does not appear to modify the absence of VP mRNA in neurons in these nuclei in the HOM rat.