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The Expression Pattern of the Na(+) Sensor, Na(X) in the Hydromineral Homeostatic Network: A Comparative Study between the Rat and Mouse.

Nehmé B, Henry M, Mouginot D, Drolet G - Front Neuroanat (2012)

Bottom Line: Here, we designed an anti-Na(X) antibody targeting the interdomain 2-3 region of the Na(X) channel's α-subunit.Na(X) immunostaining was also detected in neurons of the area postrema.In addition, Na(X) immunostaining was specifically observed in NeuN immunopositive cells in the median preoptic nucleus of the rat.

View Article: PubMed Central - PubMed

Affiliation: Axe Neurosciences du CRCHUQ (CHUL), Faculté de Médecine, Université Laval Québec, QC, Canada.

ABSTRACT
The Scn7a gene encodes for the specific sodium channel Na(X), which is considered a primary determinant of sodium sensing in the brain. Only partial data exist describing the Na(X) distribution pattern and the cell types that express Na(X) in both the rat and mouse brain. To generate a global view of the sodium detection mechanisms in the two rodent brains, we combined Na(X) immunofluorescence with fluorescent cell markers to map and identify the Na(X)-expressing cell populations throughout the network involved in hydromineral homeostasis. Here, we designed an anti-Na(X) antibody targeting the interdomain 2-3 region of the Na(X) channel's α-subunit. In both the rat and mouse, Na(X) immunostaining was colocalized with vimentin positive cells in the median eminence and with magnocellular neurons immunopositive for neurophysin associated with oxytocin or vasopressin in both the supraoptic and paraventricular nuclei. Na(X) immunostaining was also detected in neurons of the area postrema. In addition to this common Na(X) expression pattern, several differences in Na(X) immunostaining for certain structures and cell types were found between the rat and mouse. Na(X) was present in both NeuN and vimentin positive cells in the subfornical organ and the vascular organ of the lamina terminalis of the rat whereas Na(X) was only colocalized with vimentin positive cells in the mouse circumventricular organs. In addition, Na(X) immunostaining was specifically observed in NeuN immunopositive cells in the median preoptic nucleus of the rat. Overall, this study characterized the Na(X)-expressing cell types in the network controlling hydromineral homeostasis of the rat and mouse. Na(X) expression pattern was clearly different in the nuclei of the lamina terminalis of the rat and mouse, indicating that the mechanisms involved in systemic and central Na(+) sensing are specific to each rodent species.

No MeSH data available.


Distribution of NaX immunostaining in the subfornical organ of the mouse. (A) Schematic illustration of the subfornical organ (SFO) in the mouse brain (red filling). CPu, caudate putamen; fi, fimbria hippocampus; ic, internal capsule; LV, lateral ventricle; 3V, third ventricle. (B) Representative picture of the fluorescent NaX immunostaining (green) was obtained from the mouse. The cell type expressing NaX was identified using anti-NeuN, anti-GFAP, and anti-vimentin fluorescent immunostaining (red); scale bars: 50 μm. (C) Inset representing high magnification zone of the SFO; scale bar: 20 μm. The detailed zone is pointed by the arrow head (bottom-left corner of the inset). NaX staining is only present in the vimentin positive cells boarding the third ventricle.
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Figure 7: Distribution of NaX immunostaining in the subfornical organ of the mouse. (A) Schematic illustration of the subfornical organ (SFO) in the mouse brain (red filling). CPu, caudate putamen; fi, fimbria hippocampus; ic, internal capsule; LV, lateral ventricle; 3V, third ventricle. (B) Representative picture of the fluorescent NaX immunostaining (green) was obtained from the mouse. The cell type expressing NaX was identified using anti-NeuN, anti-GFAP, and anti-vimentin fluorescent immunostaining (red); scale bars: 50 μm. (C) Inset representing high magnification zone of the SFO; scale bar: 20 μm. The detailed zone is pointed by the arrow head (bottom-left corner of the inset). NaX staining is only present in the vimentin positive cells boarding the third ventricle.

Mentions: NaX immunostaining in both the rat and the mouse was detected in the CVOs, the OVLT, the SFO, the ME, and the area postrema (AP). The pattern and cellular phenotype for NaX expression in both rats and mice showed similarities only in two CVOs, which were the ME and the AP. In the ME, NaX immunostaining was essentially observed in the ventral portion of the wall of the third ventricle and in the radial processes penetrating the neuropil. NaX immunostaining colocalized with vimentin immunostaining only (Figure 3; Table 3). Intriguingly, NaX immunostaining was associated with none of the cell markers in the AP (Table 3). However, the clear regionalization of NaX immunostaining (central, lateral, and ventral zone), of vimentin staining (funiculus separans, fs) and of GFAP staining (inverted pyramidal region extending from the fs to the central canal) ruled out possible colocalization of NaX immunostaining with tanycytes or glial cells in the rat and mouse AP. In the other CVOs, NaX cellular localization was strongly divergent (Table 3). Indeed, in the rat OVLT, NaX immunostaining was dense in the cell layers boarding the third ventricle and in individual cells of the lateral periventricular tissue. NaX immunostaining colocalized with NeuN immunostaining in the lateral part of the OVLT and with vimentin immunostaining lining the third ventricle (Figure 4). In the mouse OVLT, NaX immunostaining was confined to a dense fiber network and only colocalized with vimentin immunostaining (Figure 5). NaX immunostaining was not colocalized with NeuN or GFAP immunostaining. The distribution pattern of the NaX-expressing cells was also different in the SFO of the two rodents. In the rat SFO, NaX immunostaining was present throughout the organ with a clear staining of the ependymal cell layers boarding the ventricular surface. NaX immunostaining colocalized with NeuN positive cells in both the core and periphery of the SFO, as well as with vimentin immunostaining in the ependymal cell layers (Figure 6). In the mouse SFO, NaX immunostaining was present in clusters boarding the ventricular surface. NaX immunostaining colocalized with vimentin immunostaining only (Figure 7). Overall, these results indicate that NaX is expressed in neurons and ependymocytes in the rat OVLT and SFO, and only in ependymocytes in the mouse organs (Table 3).


The Expression Pattern of the Na(+) Sensor, Na(X) in the Hydromineral Homeostatic Network: A Comparative Study between the Rat and Mouse.

Nehmé B, Henry M, Mouginot D, Drolet G - Front Neuroanat (2012)

Distribution of NaX immunostaining in the subfornical organ of the mouse. (A) Schematic illustration of the subfornical organ (SFO) in the mouse brain (red filling). CPu, caudate putamen; fi, fimbria hippocampus; ic, internal capsule; LV, lateral ventricle; 3V, third ventricle. (B) Representative picture of the fluorescent NaX immunostaining (green) was obtained from the mouse. The cell type expressing NaX was identified using anti-NeuN, anti-GFAP, and anti-vimentin fluorescent immunostaining (red); scale bars: 50 μm. (C) Inset representing high magnification zone of the SFO; scale bar: 20 μm. The detailed zone is pointed by the arrow head (bottom-left corner of the inset). NaX staining is only present in the vimentin positive cells boarding the third ventricle.
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Figure 7: Distribution of NaX immunostaining in the subfornical organ of the mouse. (A) Schematic illustration of the subfornical organ (SFO) in the mouse brain (red filling). CPu, caudate putamen; fi, fimbria hippocampus; ic, internal capsule; LV, lateral ventricle; 3V, third ventricle. (B) Representative picture of the fluorescent NaX immunostaining (green) was obtained from the mouse. The cell type expressing NaX was identified using anti-NeuN, anti-GFAP, and anti-vimentin fluorescent immunostaining (red); scale bars: 50 μm. (C) Inset representing high magnification zone of the SFO; scale bar: 20 μm. The detailed zone is pointed by the arrow head (bottom-left corner of the inset). NaX staining is only present in the vimentin positive cells boarding the third ventricle.
Mentions: NaX immunostaining in both the rat and the mouse was detected in the CVOs, the OVLT, the SFO, the ME, and the area postrema (AP). The pattern and cellular phenotype for NaX expression in both rats and mice showed similarities only in two CVOs, which were the ME and the AP. In the ME, NaX immunostaining was essentially observed in the ventral portion of the wall of the third ventricle and in the radial processes penetrating the neuropil. NaX immunostaining colocalized with vimentin immunostaining only (Figure 3; Table 3). Intriguingly, NaX immunostaining was associated with none of the cell markers in the AP (Table 3). However, the clear regionalization of NaX immunostaining (central, lateral, and ventral zone), of vimentin staining (funiculus separans, fs) and of GFAP staining (inverted pyramidal region extending from the fs to the central canal) ruled out possible colocalization of NaX immunostaining with tanycytes or glial cells in the rat and mouse AP. In the other CVOs, NaX cellular localization was strongly divergent (Table 3). Indeed, in the rat OVLT, NaX immunostaining was dense in the cell layers boarding the third ventricle and in individual cells of the lateral periventricular tissue. NaX immunostaining colocalized with NeuN immunostaining in the lateral part of the OVLT and with vimentin immunostaining lining the third ventricle (Figure 4). In the mouse OVLT, NaX immunostaining was confined to a dense fiber network and only colocalized with vimentin immunostaining (Figure 5). NaX immunostaining was not colocalized with NeuN or GFAP immunostaining. The distribution pattern of the NaX-expressing cells was also different in the SFO of the two rodents. In the rat SFO, NaX immunostaining was present throughout the organ with a clear staining of the ependymal cell layers boarding the ventricular surface. NaX immunostaining colocalized with NeuN positive cells in both the core and periphery of the SFO, as well as with vimentin immunostaining in the ependymal cell layers (Figure 6). In the mouse SFO, NaX immunostaining was present in clusters boarding the ventricular surface. NaX immunostaining colocalized with vimentin immunostaining only (Figure 7). Overall, these results indicate that NaX is expressed in neurons and ependymocytes in the rat OVLT and SFO, and only in ependymocytes in the mouse organs (Table 3).

Bottom Line: Here, we designed an anti-Na(X) antibody targeting the interdomain 2-3 region of the Na(X) channel's α-subunit.Na(X) immunostaining was also detected in neurons of the area postrema.In addition, Na(X) immunostaining was specifically observed in NeuN immunopositive cells in the median preoptic nucleus of the rat.

View Article: PubMed Central - PubMed

Affiliation: Axe Neurosciences du CRCHUQ (CHUL), Faculté de Médecine, Université Laval Québec, QC, Canada.

ABSTRACT
The Scn7a gene encodes for the specific sodium channel Na(X), which is considered a primary determinant of sodium sensing in the brain. Only partial data exist describing the Na(X) distribution pattern and the cell types that express Na(X) in both the rat and mouse brain. To generate a global view of the sodium detection mechanisms in the two rodent brains, we combined Na(X) immunofluorescence with fluorescent cell markers to map and identify the Na(X)-expressing cell populations throughout the network involved in hydromineral homeostasis. Here, we designed an anti-Na(X) antibody targeting the interdomain 2-3 region of the Na(X) channel's α-subunit. In both the rat and mouse, Na(X) immunostaining was colocalized with vimentin positive cells in the median eminence and with magnocellular neurons immunopositive for neurophysin associated with oxytocin or vasopressin in both the supraoptic and paraventricular nuclei. Na(X) immunostaining was also detected in neurons of the area postrema. In addition to this common Na(X) expression pattern, several differences in Na(X) immunostaining for certain structures and cell types were found between the rat and mouse. Na(X) was present in both NeuN and vimentin positive cells in the subfornical organ and the vascular organ of the lamina terminalis of the rat whereas Na(X) was only colocalized with vimentin positive cells in the mouse circumventricular organs. In addition, Na(X) immunostaining was specifically observed in NeuN immunopositive cells in the median preoptic nucleus of the rat. Overall, this study characterized the Na(X)-expressing cell types in the network controlling hydromineral homeostasis of the rat and mouse. Na(X) expression pattern was clearly different in the nuclei of the lamina terminalis of the rat and mouse, indicating that the mechanisms involved in systemic and central Na(+) sensing are specific to each rodent species.

No MeSH data available.