Changes in the arginine-vasopressin immunoreactive systems in male mice lacking a functional aromatase gene

Oxytocin, but not oxytocin receptor, is rRegulated by oestrogen receptor beta in the female mouse hypothalamus

In the female rat, oestrogen receptor (ER) beta is colocalized with both oxytocin- and vasopressin-producing neurones in the paraventricular nucleus of the hypothalamus (PVN). In this study, we demonstrate that the same pattern of colocalization between ERbeta and oxytocin exists in the female mouse. Because this nucleus contains only a negligible quantity of ERalpha, it is likely that the oestrogen-dependent regulation of oxytocin and vasopressin synthesis in the PVN is mediated by ERbeta. Thus, we compared the effect of ovarian hormones on oxytocin and vasopressin mRNA expression in the PVN of wild-type (WT) and ERbeta knockout (betaERKO) mice. We also compared the effects of ovarian hormones on oxytocin receptor (OTR) expression in the medial amygdala (MeA) and ventromedial nucleus of the hypothalamus (VMN) in female WT and betaERKO mice. Ovariectomized mice underwent long-term treatment with oestradiol or oil. Progesterone was given concurrently on the final 7 days of treatment, and all mice were killed 48 h after the final progesterone injection. In the PVN, hormone treatment increased oxytocin mRNA expression in WT but not betaERKO females. These results suggest that ERbeta is necessary for the regulation of the expression of oxytocin in the PVN. Hormone treatment had no effect on vasopressin mRNA expression in the PVN, but significantly increased OTR binding in both the VMN and the MeA in both genotypes. Collectively, our data show region and peptide specific regulation by ERalpha and ERbeta in the mouse hypothalamus.

Anatomical relationships between aromatase-immunoreactive neurons and nitric oxide synthase as evidenced by NOS immunohistochemistry or NADPH diaphorase histochemistry in the quail forebrain

In Japanese quail (Coturnix japonica), previous studies indicated that the distribution of reduced nicotinamide dinucleotide phosphate (NADPH) diaphorase overlaps with steroid-sensitive areas that contain dense populations of aromatase-immunoreactive (ARO-ir) cells. We investigated here the anatomical relationships between aromatase (ARO) and nitric oxide synthase (NOS)-containing cells that were visualized both by NOS-immunohistochemistry and NADPH-histochemistry. The distribution of ARO-ir and of NADPH-positive cells in the forebrain observed here matched exactly the distribution previously reported. The distribution of NOS-immunoreactive material in the vicinity of ARO-ir cell groups appeared similar to the distribution of NADPH-positive structures previously identified by histochemistry. The number of NOS-immunoreactive cells was similar to the number of NADPH-positive cells and they were found in the same brain regions. In contrast, few NOS-immunoreactive fibers were observed whereas numerous NADPH-positive fibers and punctuate structures were present in many areas. Major groups of NOS-immunoreactive/NADPH-positive neurons were adjacent to the main ARO-ir cell groups, such as the medial preoptic nucleus, the bed nucleus of the stria terminalis and the nucleus ventromedialis hypothalamic. However, examination of adjacent sections indicated that there is very little overlap between the NOS-immunoreactive and ARO-ir cell populations. This notion got further support by double-labeled sections where no double-labeled cells could be identified. In sections stained simultaneously by histochemistry for NADPH and immunohistochemistry for ARO, many NADPH-positive fibers and punctate structures were closely associated with ARO-ir perikarya. Taken together, the present data indicate that NOS is not or very rarely colocalized with ARO but that NOS inputs are closely associated with ARO-ir cells. Based on previous work in a variety of model systems, it can be hypothesized that these inputs modulate the expression or activity of ARO in the quail brain.