Neuronal nitric oxide synthase and calbindin delineate sex differences in the developing hypothalamus and preoptic area - PubMed (original) (raw)

Neuronal nitric oxide synthase and calbindin delineate sex differences in the developing hypothalamus and preoptic area

Michelle Edelmann et al. Dev Neurobiol. 2007.

Abstract

Throughout the hypothalamus there are several regions known to contain sex differences in specific cellular, neurochemical, or cell grouping characteristics. The current study examined the potential origin of sex differences in calbindin expression in the preoptic area and hypothalamus as related to sources of nitric oxide. Specific cell populations were defined by immunoreactive (ir) calbindin and neuronal nitric oxide synthase (nNOS) in the preoptic area/anterior hypothalamus (POA/AH), anteroventral periventricular nucleus (AVPv), and ventromedial nucleus of the hypothalamus (VMN). The POA/AH of adult mice was characterized by a striking sex difference in the distribution of cells with ir-calbindin. Examination of the POA/AH of androgen receptor deficient Tfm mice suggests that this pattern was in part androgen receptor dependent, since Tfm males had reduced ir-calbindin compared with wild-type males and more similar to wild-type females. At P0 ir-calbindin was more prevalent than in adulthood, with males having significantly more ir-calbindin and nNOS than have females. Cells that contained either ir-calbindin or ir-nNOS in the POA/AH were in adjacent cell groups, suggesting that NO derived from the enzymatic activity of nNOS may influence the development of ir-calbindin cells. In the region of AVPv, at P0, there was a sex difference with males having more ir-nNOS fibers than have females while ir-calbindin was not detected. In the VMN, at P0, ir-nNOS was greater in females than in males, with no significant difference in ir-calbindin. We suggest that NO as an effector molecule and calbindin as a molecular biomarker illuminate key aspects of sexual differentiation in the developing mouse brain.

PubMed Disclaimer

Figures

Figure 1

Sagittal section of the mouse brain illustrates different angles of sectioning (A, B, or C), which create alternate ventral/dorsal alignments of brain regions. In coronal plane A, the preoptic area overlays different regions of the anterior hypothalamus than in coronal plane B or C. AVPV, anteroventral periventricular nucleus of the preoptic area; POA, preoptic area; ac, anterior commisure, OC, optic chiasm; Fx, fornix; AH, anterior hypothalamus; ARC, arcuate; VMN, ventromedial nucleus of the hypothalamus.

Figure 2

In the POA/AH, adult C57BL/6J mice, males and females differed in the total number of cells that contained immunoreactive calbindin. Males (A) had more ir-calbindin cells and fibers than females (B), p < 0.01 (data are mean ± SEM). Positional analysis shows that the sex difference was primarily due to fourfold differences in the amount of ir-calbindin at 100–200 _μ_m away from the third ventricle (C). Similarly, in the POA/AH of weanling males, females, and Tfm mice, the areas of ir-calbindin differed significantly (D). Wild-type males had three to four times the amount of ir-calbindin than had wild-type females and had 2–3-fold more ir-calbindin than had Tfm mice, whether measured in dorsal/ventral distances away from the AC or in medial/lateral distances from the third ventricle (D), p < 0.01 (data are mean ± SEM). AC, anterior commissure; V, third ventricle.

Figure 3

In the POA/AH at birth (P0) male mice had more immunoreactive nNOS and calbindin cells and fibers than had females. Sex differences were found approximately 200–400 _μ_m lateral to the third ventricle (C) with more ir-nNOS in males (A) than in females (B). Differences in nNOS expression occurred dorsally, ventral to the AC (black arrowheads), and in a ventral stripe of cells that was oriented medial/lateral (black arrows). ir-Calbindin was more densely localized in males (D) compared to more spread in females (E, white arrowheads). Males and females differed in the total number of cells that contained ir-calbindin (F), p < 0.01 (data are mean ± SEM). AC, anterior commissure; V, third ventricle.

Figure 4

In the POA/AH, a striking relationship was seen in the apposition of cells containing immunoreactive nNOS and calbindin at P0. A pseudocolor overlay of adjacent sections containing nNOS-ir (red) or calbindin-ir (green) illustrates this apposition (A). The box in the overlay image of panel A depicts the approximate location of the boundary in the fluorescent double-label experiment (B). Dense ir-nNOS (red) was located adjacent to the third ventricle and ir-calbindin (green) was found just lateral and ventral to ir-nNOS.

Figure 5

In the region of AVPv at birth (P0), males (A) and females (B) differed in the amount of fibers containing immunoreactive nNOS. Males had 300% more ir-nNOS than females (C, **p < 0.01; data are mean ± SEM). V, third ventricle.

Figure 6

In the VMN at birth (P0) males and females differed in the amount of cells and fibers containing ir-nNOS, but not ir-calbindin. Females (B) had more ir-nNOS than had males (A) as illustrated in the graph of mean immunoreactive areas (C, *p < 0.05; data are mean ± SEM). There was no significant difference in the amount of ir-calbindin between males (D) and females (E) as depicted by the graph (F). V, third ventricle.

References

1. Arai V, Murakami S, Nishizuka M. Androgen enhances neuronal degeneration in the developing preoptic area: apoptosis in the anteroventral periventricular nucleus (AVPvN-POA) Horm Behav. 1994;28:313–319. - PubMed
1. Arnold AP. Sex chromosomes and brain gender. Nat Rev Neurosci. 2004;5:701–708. - PubMed
1. Bicker G. STOP and GO with NO: Nitric oxide as a regulator of cell motility in simple brains. Bioessays. 2005;27:495–505. - PubMed
1. Bisenius ES, Veeramachaneni DN, Sammonds GE, Tobet S. Sex differences and the development of the rabbit brain: Effects of vinclozolin. Biol Reprod. 2006:75. (Epub ahead of print) - PubMed
1. Bloch GJ, Eckersell C, Mills R. Distribution of galanin-immunoreactive cells within sexually dimorphic components of the medial preoptic area of the male and remale rat. Brain Res. 1993;620:259–268. - PubMed

Neuronal nitric oxide synthase and calbindin delineate sex differences in the developing hypothalamus and preoptic area - PubMed (original) (raw)