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Adenovector GAD65 gene delivery into the rat trigeminal ganglion produces orofacial analgesia.

Vit JP, Ohara PT, Sundberg C, Rubi B, Maechler P, Liu C, Puntel M, Lowenstein P, Castro M, Jasmin L - Mol Pain (2009)

Bottom Line: We postulated that GABA produced from the expression of GAD would reduce pain behavior by acting on GABA receptors on neurons within the ganglion.GABA receptors were not found on SGCs.Six days after injection of AdGAD65 into the trigeminal ganglion, there was a statistically significant decrease of pain behavior in the orofacial formalin test, a model of inflammatory pain.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anatomy, University of California San Francisco, San Francisco, CA 94143, USA. Jeanpvit@gmail.com

ABSTRACT

Background: Our goal is to use gene therapy to alleviate pain by targeting glial cells. In an animal model of facial pain we tested the effect of transfecting the glutamic acid decarboxylase (GAD) gene into satellite glial cells (SGCs) of the trigeminal ganglion by using a serotype 5 adenovector with high tropisms for glial cells. We postulated that GABA produced from the expression of GAD would reduce pain behavior by acting on GABA receptors on neurons within the ganglion.

Results: Injection of adenoviral vectors (AdGAD65) directly into the trigeminal ganglion leads to sustained expression of the GAD65 isoform over the 4 weeks observation period. Immunohistochemical analysis showed that adenovirus-mediated GAD65 expression and GABA synthesis were mainly in SGCs. GABAA and GABAB receptors were both seen in sensory neurons, yet only GABAA receptors decorated the neuronal surface. GABA receptors were not found on SGCs. Six days after injection of AdGAD65 into the trigeminal ganglion, there was a statistically significant decrease of pain behavior in the orofacial formalin test, a model of inflammatory pain. Rats injected with control virus (AdGFP or AdLacZ) had no reduction in their pain behavior. AdGAD65-dependent analgesia was blocked by bicuculline, a selective GABAA receptor antagonist, but not by CGP46381, a selective GABAB receptor antagonist.

Conclusion: Transfection of glial cells in the trigeminal ganglion with the GAD gene blocks pain behavior by acting on GABAA receptors on neuronal perikarya.

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Sensory neurons of the trigeminal ganglion express both GABAA and GABAB receptors. GABAA receptor immunostaining of ganglion neurons is membrane associated (A1, red, arrows) while GABAB immunostaining is cytoplasmic (A2) The combined image (A3) shows some neurons are double labelled for GABAA receptor and GABAB receptor (A3, arrows). Scale bar = 30 μm
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Figure 4: Sensory neurons of the trigeminal ganglion express both GABAA and GABAB receptors. GABAA receptor immunostaining of ganglion neurons is membrane associated (A1, red, arrows) while GABAB immunostaining is cytoplasmic (A2) The combined image (A3) shows some neurons are double labelled for GABAA receptor and GABAB receptor (A3, arrows). Scale bar = 30 μm

Mentions: In view of the previous results, we sought to determine if AdGAD65 produced its antinociceptive effect locally in the trigeminal ganglion through the activation of GABA receptors. We first confirmed that GABAA and GABAB receptors were expressed in sensory neurons of the trigeminal ganglion (Figure 4). GABAA receptor expression appeared as light cytoplasmic immunostaining with stronger intensity at the surface of the cell bodies of the sensory neurons (Figure 4A and 4C). The expression of GABAB receptors was only found in the cytoplasm of sensory neurons (Figure 4B and 4C). Both GABAA and GABAB receptors were seen in all types of sensory neurons.


Adenovector GAD65 gene delivery into the rat trigeminal ganglion produces orofacial analgesia.

Vit JP, Ohara PT, Sundberg C, Rubi B, Maechler P, Liu C, Puntel M, Lowenstein P, Castro M, Jasmin L - Mol Pain (2009)

Sensory neurons of the trigeminal ganglion express both GABAA and GABAB receptors. GABAA receptor immunostaining of ganglion neurons is membrane associated (A1, red, arrows) while GABAB immunostaining is cytoplasmic (A2) The combined image (A3) shows some neurons are double labelled for GABAA receptor and GABAB receptor (A3, arrows). Scale bar = 30 μm
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2734545&req=5

Figure 4: Sensory neurons of the trigeminal ganglion express both GABAA and GABAB receptors. GABAA receptor immunostaining of ganglion neurons is membrane associated (A1, red, arrows) while GABAB immunostaining is cytoplasmic (A2) The combined image (A3) shows some neurons are double labelled for GABAA receptor and GABAB receptor (A3, arrows). Scale bar = 30 μm
Mentions: In view of the previous results, we sought to determine if AdGAD65 produced its antinociceptive effect locally in the trigeminal ganglion through the activation of GABA receptors. We first confirmed that GABAA and GABAB receptors were expressed in sensory neurons of the trigeminal ganglion (Figure 4). GABAA receptor expression appeared as light cytoplasmic immunostaining with stronger intensity at the surface of the cell bodies of the sensory neurons (Figure 4A and 4C). The expression of GABAB receptors was only found in the cytoplasm of sensory neurons (Figure 4B and 4C). Both GABAA and GABAB receptors were seen in all types of sensory neurons.

Bottom Line: We postulated that GABA produced from the expression of GAD would reduce pain behavior by acting on GABA receptors on neurons within the ganglion.GABA receptors were not found on SGCs.Six days after injection of AdGAD65 into the trigeminal ganglion, there was a statistically significant decrease of pain behavior in the orofacial formalin test, a model of inflammatory pain.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anatomy, University of California San Francisco, San Francisco, CA 94143, USA. Jeanpvit@gmail.com

ABSTRACT

Background: Our goal is to use gene therapy to alleviate pain by targeting glial cells. In an animal model of facial pain we tested the effect of transfecting the glutamic acid decarboxylase (GAD) gene into satellite glial cells (SGCs) of the trigeminal ganglion by using a serotype 5 adenovector with high tropisms for glial cells. We postulated that GABA produced from the expression of GAD would reduce pain behavior by acting on GABA receptors on neurons within the ganglion.

Results: Injection of adenoviral vectors (AdGAD65) directly into the trigeminal ganglion leads to sustained expression of the GAD65 isoform over the 4 weeks observation period. Immunohistochemical analysis showed that adenovirus-mediated GAD65 expression and GABA synthesis were mainly in SGCs. GABAA and GABAB receptors were both seen in sensory neurons, yet only GABAA receptors decorated the neuronal surface. GABA receptors were not found on SGCs. Six days after injection of AdGAD65 into the trigeminal ganglion, there was a statistically significant decrease of pain behavior in the orofacial formalin test, a model of inflammatory pain. Rats injected with control virus (AdGFP or AdLacZ) had no reduction in their pain behavior. AdGAD65-dependent analgesia was blocked by bicuculline, a selective GABAA receptor antagonist, but not by CGP46381, a selective GABAB receptor antagonist.

Conclusion: Transfection of glial cells in the trigeminal ganglion with the GAD gene blocks pain behavior by acting on GABAA receptors on neuronal perikarya.

Show MeSH
Related in: MedlinePlus