Estrogen configures sexual dimorphism in the preoptic area of C57BL/6J and ddN strains of mice

Abstract

Immunohistochemistry using a calbindin D28k antibody revealed a marked sex difference in neuronal distribution in the central portion of the medial preoptic area in C57BL/6J and ddN strains of mice when the animals were sacrificed on D65 (D1 = the day of birth). Male mice had a distinct ellipsoidal cell aggregate, whereas females lacked such a structure. This sex difference was not observed in Nissl-stained sections. Co-localization of calbindin D28k and the neuron-specific nuclear protein NeuN confrmed that the cells in the aggregate were neurons. The aggregates were larger in males than in females in both strains. When observed on D65, males orchidectomized on D1 had smaller aggregates. However, daily injections of 2 microg estradiol benzoate through D1-D5 as well as a single injection of 100 microg testosterone propionate on D1 enlarged the aggregates in females, but a single injection of 100 microg dihydrotestosterone on D1 had no effect on the female phenotype. Similar endocrine manipulations had no effects in adult animals of both sexes. Thus, the calbindin-immunoreactive cell aggregates in the preoptic area of C57BL/6J and ddN mice are homologous to the sexually dimorphic nucleus of the rat preoptic area in terms of the morphology and sex steroid-dependent organization.

Functional, anatomical, and neurochemical differentiation of medial preoptic area subregions in relation to maternal behavior in the mouse

“…The general distribution of molecules identified in this study using virgin female mice was largely consistent with previous studies in mice (Castel and Morris, 1988;Orikasa and Sakuma, 2010;Hrabovszky et al, 2012;Mar et al, 2012) and rats (Melander et al, 1986;Simerly et al, , 1990Okamura et al, 1990;Alexander et al, 1991;Veinante and FreundMercier, 1997). It is noteworthy, however, that reproductive experience and estrous cycling might cause specific changes in molecular expression .…”

“…For calbindin D-28K we used a mouse monoclonal antibody. The labeling produced in this antibody was consistent with that of previous studies using another anti-calbindin antibody in the mouse MPOA (Orikasa and Sakuma, 2010). For green fluorescent protein (GFP) we used a rabbit polyclonal antibody to detect the expression of Venus in Oxtr Tsuneoka et al…”

“…A cluster of calbindin-ir cell bodies was found in the specific subregion of MPNm, known as sexually dimorphic nucleus in the mouse MPOA (Fig. 3G) (Edelmann et al, 2007;Orikasa and Sakuma, 2010), and PDPN. The distributions of c-Fos-ir neurons and CB-ir cell bodies did not match each other.…”

The densities of calbindin and parvalbumin, but not calretinin neurons, are sexually dimorphic in the amygdala of the guinea pig

“…Moreover, there is a direct evidence that some CBþ neurons are projecting neurons (Moryś et al, 1999;McDonald et al, 2012). The next important fact is that both, CBþ (present study) and GABAþ (Stefanova, 1998) neurons are in the amygdala sexually dimorphic as they are also in several other brain regions Orikasa and Sakuma, 2010;Yahr, 2011). Moreover, both, CBþ and GABAþ neurons are in the amygdala and several other brain regions dependent on sex hormones (Stefanova, 1998;Sickel and McCarthy, 2000;Stuart et al, 2001;Yahr, 2011).…”

Sexual Behavior: From Hormonal Regulation to Endocrine Disruption

“…Differences in cell number and morphology or fiber density between the sexes have frequently been described for the medial amygdala, the bed nucleus of the stria terminalis, and the medial preoptic area [12]. For instance, the rat sexually dimorphic nucleus (SDN) and corresponding cluster of calbindin-immunoreactive neurons, both located in the medial preoptic area, contain more cells in males than in females [13, 14]. Conversely, neurons expressing kisspeptin and tyrosine hydroxylase in the anteroventral periventricular (AVPV) nucleus, a subdivision of the preoptic area involved in the ovulatory surge of LH, are more numerous in females than in males [15-17].…”