The medial habenula contains a specific nonstellate subtype of astrocyte expressing the ectonucleotidase NTPDase2

Abstract

ATP-mediated synaptic transmission represents the only transmitter-gated Ca(2+)-entry pathway in neurons of the rodent medial habenula. In addition to direct purinergic receptor-mediated synaptic inputs, the medial habenula contains purinergic systems that modulate synaptic transmission. Purinergic signaling is modulated or terminated by ectonucleotidase, nucleotide-hydrolyzing enzymes of the cell surface. Here we identify the major ectonucleotidase responsible for the hydrolysis of extracellular ATP in the mouse medial habenula as ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2), using immunostaining and enzyme histochemistry. Double labeling experiments reveal that the enzyme is expressed by astrocytes enwrapping the densely packed neurons and also the myelinated fiber bundles of the stria medullaris. NTPDase2 immunoreactivity is absent from the lateral habenula. The analysis of mice expressing enhanced green fluorescent protein under the promoter of glial fibrillary acidic protein revealed that the medial habenula harbors a highly polar type of astrocytes with very long laminar cellular processes, untypical for grey matter astrocytes. Its morphology strongly differs from that of the stellate astrocytes in the adjacent lateral habenula. Our results suggest that the mouse medial habenula contains a specific perineuronal nonstellate subtype of astrocyte that expresses the ectonucleotidase NTPDase2 and is in a strategic position to modulate purinergic transmission in this subnucleus.

Vascular and extravascular distribution of the ATP-binding cassette transporters ABCB1 and ABCC1 in aged human brain and pituitary

“…A particularly intriguing result of our study is the occurrence of ABCB1 and ABCC1 in certain neurons, because their regional distribution pattern closely resembles that of brain areas with adenosinergic and/or purinergic cell signalling (recently summarized by (Abbracchio et al, 2009; Burnstock, 2007; Burnstock, 2013; Burnstock et al, 2011; Gampe et al, 2012; Mutafova-Yambolieva and Durnin, 2014). To learn more about a possible connection between neuronal localization of both transporter proteins and this particular type of neuromodulation, we compared the distribution of ABCB1 and ABCC1 with those of 5-N´ ADA and NTPDase2.…”

“…When doing this, we were able to identify numerous NTPDase2 immunolabelled, nonstellate astroglial cells (Fig. 5E), which are regarded typical for the presence of purinergic neurotransmission (at least in the rat; Gampe et al (2012)). Interestingly, we could confirm the observation made by Gampe et al (2012) that NTPDase2 partly co-localizes with GFAP in the medial but not in the lateral habenula (Fig.…”

“…This intracellular localization of ABCB1 might be of relevance in light of a recently discovered contribution of lysosomes to ABCB1 cell drug delivery (Yamagishi et al, 2013). Since subpopulations of neurons located in the above listed brain regions have repeatedly been linked with aspects of purinergic and/or adenosinergic neuromodulation (for a recent comprehensive reviews see Gampe et al (2012) and especially Mutafova-Yambolieva and Durnin (2014), decided to look for three putative cell markers for adenosinergic/purinergic cell signalling (i.e. ADA, 5´-N and NTPDase2).…”

“…However, the occurrence of ADA and 5-N´ immunoreactivities was not restricted to circumscribed ABCB1 or ABCC1 immunopositive nerve cell populations, but were found to be more widely distributed throughout human brain (not shown). Therefore, we introduced a third cellular marker, the NTPDase2, which is regarded a good morphologic indicator of purinergic neurotransmission in the rat medial habenula (Gampe et al, 2012). When doing this, we were able to identify numerous NTPDase2 immunolabelled, nonstellate astroglial cells (Fig.…”

“…5E), which are regarded typical for the presence of purinergic neurotransmission (at least in the rat; Gampe et al (2012)). Interestingly, we could confirm the observation made by Gampe et al (2012) that NTPDase2 partly co-localizes with GFAP in the medial but not in the lateral habenula (Fig. 5G and H), and with another suitable astroglial marker, glutamine synthetase (Fig.…”