Differential distribution of glutamate decarboxylase-65 and glutamate decarboxylase-67 messenger RNAs in the entopeduncular nucleus of the rat
Section snippets
Animals
Female rats (200–250 g) of an outbred Sprague–Dawley strain (ALAB, Sollentuna, Sweden) were used for these experiments. The animals were housed at approximately 22°C on a fixed light cycle (12 h light–12 h dark), with food and water available at all times. Animals were rendered unconscious by CO2 inhalation to minimize discomfort and decapitated. Brains were rapidly removed, frozen with powdered dry ice and either used immediately (northern analysis) or stored for up to one week at −70°C (in situ
Specificity of glutamate decarboxylase-65 and glutamate decarboxylase-67 oligodeoxyribonucleotide probes
Northern analysis performed on poly(A)+-enriched mRNA preparations from whole rat brain showed that the GAD65 and GAD67 oligodeoxynucleotide probes used in the present study labelled mRNAs of approximately 5.7 and 3.7 kb (Fig. 1).
Film autoradiograms demonstrating GAD65 and GAD67 mRNA labelling in brain sections collected at several levels of the striatum and pallidal complex are shown in Fig. 2. Both GAD mRNA probes labelled brain regions known to contain GABAergic neurons with high resolution
Discussion
In the present study, recently developed oligodeoxynucleotide probes[19]were used to describe the distribution of GAD65 and GAD67 mRNAs in the EP. Analysis of film autoradiograms comparing the distribution of the two isoforms of the GAD enzyme throughout the entire extent of the EP demonstrated a clear difference in the distribution of GAD65 and GAD67 mRNAs. More specifically, GAD65 mRNA labelling was most abundant in the rostral two-thirds of the EP, with lower but detectable levels in the
Conclusion
The results of the present study provide an additional neurochemical marker for discriminating the limbic and motor pathways through one of the major output nuclei of the basal ganglia, the EP. In doing so, these data, along with previously published reports, provide further evidence for a possible means whereby neurotransmission through motor and limbic pathways of the basal ganglia are integrated via a habenular–raphé–striatal circuit involving serotonin.
Acknowledgements
This work was supported by grant no. 8318 from the Swedish Medical Research Council.
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2008, NeuroscienceCitation Excerpt :It was also reported that the entopedunculo-habenular pathway in the rat was a GABAergic system (Nagy et al., 1978), and that Ep neurons sending their axons to the lateral habenular nucleus expressed somatostatin immunoreactivity (Vincent and Brown, 1986). Direct projections from the Ep to the lateral habenular nucleus have been considered to be a major projection pathway from the Ep in the rat (Kha et al., 2000; for further review, see Rajakumar et al., 1993), and it appears to be often assumed that the rostral Ep constitutes a limbic pathway via direct projections to the lateral habenular nucleus, while the caudal Ep is involved in motor functions via projections to the thalamic and lower brainstem regions (van der Kooy and Carter, 1981; Rajakumar et al., 1993; Yuan et al., 1997). However, it has been demonstrated in the rat that the rostral Ep projects not only to the habenular nucleus but also to the SC and lateral tegmental field (Takada et al., 1994), and that the lateral habenular nucleus projects not only to the limbic function-related regions, such as the septum, hypothalamus, central gray, and midbrain raphe nuclei, but also to the ventral tegmental area, substantia nigra and zona incerta (Pasquier et al., 1976; Herkenham and Nauta, 1977, 1979).
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