Glial coverage of the small cell somata in the rat nucleus of tractus solitarius during postnatal development

Abstract

Astrocytes are thought to be active participants in synaptic plasticity in the developing nervous system. Previous studies suggested that axosomatic synapses decreased in number on the small cells of the rat caudal nucleus of tractus solitarius (cNTS) toward the end of the first postnatal week. Astrocytes might be involved in this phenomenon. We examined the morphological development of astrocytic processes around the small cell soma in the rat cNTS using light and electron microscopy. Glial fibrillary acidic protein (GFAP), glutamate-aspartate transporter (GLAST), and glutamate transporter-1 (GLT-1)-positive structures within the cNTS became more intensely stained as development proceeded. GLAST-positive structures encompassed calbindinpositive small cell somata after postnatal day 10. Electron microscopic observations indicated that astrocytic processes encompass the small cell soma, while the number of axosomatic synapses decreases as development proceeds. The timing for glial coverage of the small cell soma appears to be consistent with the decrease in axosomatic synapses on the small cells. These observations imply that astrocytes may participate actively in regulating the decrease of axosomatic synapses on small cells in the cNTS during postnatal development. V V C 2007 Wiley-Liss, Inc.

Glial EAAT2 regulation of extracellular nTS glutamate critically controls neuronal activity and cardiorespiratory reflexes

“…Taken together, these data demonstrate that nTS astrocyte transporters regulate glutamate signalling and neuronal excitability via AMPARs to shape baseline and reflex cardiorespiratory function. Consistent with our previous study ) and others (Tashiro & Kawai, 2007;Chounlamountry & Kessler, 2011), EAAT2 was highly expressed throughout the nTS, including surrounding VGluT2-labelled (glutamatergic) terminals, and thus is well positioned to modulate synaptic and neuronal function. EAAT2 is believed to be the primary glial glutamate transporter in the nTS, with its location within the astrocytic cell body and processes (Tashiro & Kawai, 2007).…”

Intrinsic properties of rostral ventrolateral medulla presympathetic and bulbospinal respiratory neurons of juvenile rats are not affected by chronic intermittent hypoxia

“…Moreover, it is after P21 that the processes of myelination, formation of the extracellular matrix and perineuronal net (Morales et al . ) and wrapping of neuronal cell bodies by astroglial processes (Tashiro & Kawai, ) reach levels similar to those observed in adult rats. It is important to note that the difficulties in patch clamping RVLM neurons in slices from juvenile or adult rats are due to the full myelination and expression of the extracellular matrix and perineuronal net.…”

“…The significance of such experiments in juvenile rats (P35) relies on the fact that the density and spatial distribution of ion channels (Beckh et al 1989;Magee & Johnston, 1995;Gong et al 1999;Straka et al 2005) and the expression and functional properties of synaptic receptors (Ben-Ari, 2002;Luján et al 2005) are fully established only several days after birth (P21). Moreover, it is after P21 that the processes of myelination, formation of the extracellular matrix and perineuronal net (Morales et al 2004) and wrapping of neuronal cell bodies by astroglial processes (Tashiro & Kawai, 2007) reach levels similar to those observed in adult rats. It is important to note that the difficulties in patch clamping RVLM neurons in slices from juvenile or adult rats are due to the full myelination and expression of the extracellular matrix and perineuronal net.…”

Glial cells modulate the synaptic transmission of NTS neurons sending projections to ventral medulla of Wistar rats

“…As NTS presents a density of glial cells higher than other brainstem areas (Pecchi et al. ) and there is ultrastructural evidence of tripartite synapses in the NTS (Tashiro and Kawai ; Chounlamountry and Kessler ), in this study, we documented that putative astrocytes in the NTS modulate the spontaneous neuronal transmission and the synaptic activity in response to TS stimulation. For this purpose, we patched putative NTS astrocytes and evaluated their sensitivity to TS stimulation.…”

“…Considering that TS stimulation induces glutamate release and produces an TS-EPSCs in the NTS-VLM neurons (Accorsi-Mendonc ßa et al, 2007), and also that astrocytes are around the synaptic cleft of NTS neurons (Tashiro and Kawai 2007) we induced the putative astrocytes inhibition to evaluate their role in the response of NTS-VLM neurons after TS stimulation.…”