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Up-regulation of metabotropic glutamate receptor 3 mRNA expression in the cerebral cortex of monoarthritic rats
F L Neto1, J Schadrack, S Platzer
1Institute of Histology and Embryology and IBMC, Faculty of Medicine of Oporto, Porto, Portugal.
Abstract:
Metabotropic glutamate receptors (mGluR) have been shown to play a role in the modulation of acute and inflammatory pain. Additionally, we have recently detected time-dependent changes in the mRNA expression of several mGluR subtypes in thalamic nuclei of monoarthritic (MA) rats. In the present study, mGluR1, -3, -4, and -7 subtype mRNA expression was analyzed by in situ hybridization with radioactively labelled oligonucleotide probes in cerebral cortical regions of normal and MA rats at 2, 4, and 14 days of the disease. The mGluR1, -4, and -7 mRNAs were at background level in normal rats and did not change in MA animals. In contrast, mGluR3 mRNA expression was abundant in normal rats and was significantly increased in cortical areas of MA rats at all time points. Higher changes were detected bilaterally at 4 days, predominantly in layers IV/V, in the motor, primary, and secondary somatosensory cortices (average increases of 50-75%), but maximum rises occurred in the contralateral cingulate cortex (+138%). No changes were detected in the auditory cortex. The present data show an up-regulation of mGluR3 mRNA expression in the motor, somatosensory, and limbic cortices of MA rats. This possibly reflects the occurrence of central mechanisms counteracting the increased transmission of nociceptive input arising from the inflamed paw and the impaired motor behavior of these rats. Changes in the cingulate cortex may be related to the motivational-affective component of nociception.
Insights
Metabotropic glutamate receptors (mGluR) play a role in pain modulation. In monoarthritic rats, mGluR3 mRNA expression significantly increased in cortical areas, suggesting central mechanisms involved in pain and motor behavior regulation.
Area of Science:
- Neuroscience
- Molecular Biology
- Pain Research
Background:
- Metabotropic glutamate receptors (mGluRs) modulate pain signaling.
- Previous studies indicated time-dependent mGluR mRNA changes in the thalamus of monoarthritic (MA) rats.
Purpose of the Study:
- To investigate mGluR subtype mRNA expression in the cerebral cortex of MA rats.
- To analyze changes in mGluR1, -3, -4, and -7 mRNA expression at different time points during the disease.
Main Methods:
- In situ hybridization using radioactively labeled oligonucleotide probes.
- Analysis of mGluR mRNA expression in cortical regions of normal and MA rats.
- Time course analysis at 2, 4, and 14 days post-induction of monoarthritis.
Main Results:
- mGluR1, -4, and -7 mRNA levels remained at background or unchanged in MA rats.
- mGluR3 mRNA expression was significantly upregulated in cortical areas of MA rats at all time points.
- Maximum increases in mGluR3 mRNA were observed in the cingulate cortex, motor cortex, and somatosensory cortices.
Conclusions:
- The study demonstrates an upregulation of mGluR3 mRNA in specific cortical regions of MA rats.
- This upregulation may reflect central compensatory mechanisms against nociceptive input and motor impairments.
- Changes in the cingulate cortex suggest a role in the emotional-affective aspects of pain.