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Development profile of metabotropic glutamate receptor mRNA in rat brain
D F Condorelli1, P Dell'Albani, C Amico
1Institute of Biochemistry, University of Catania, School of Medicine, Italy.
Abstract:
We have studied the expression of metabotropic glutamate receptor (mGluR) mRNA by Northern blot analysis with a specific cDNA probe (the pmGR1 probe). In 1-day-old rats, the steady state levels of mRNA were higher in the hypothalamus and olfactory bulb, with intermediate levels in the cerebellum and low levels in the hippocampus and cerebral cortex. In the olfactory bulb, hypothalamus, and cerebral cortex, the expression of mGluR mRNA remained constant at 8 and 30 days of postnatal life. In contrast, in the cerebellum and hippocampus, mRNA levels increased progressively with age. There was no correlation between levels of mGluR mRNA and stimulation of polyphosphoinositide hydrolysis by 1-aminocyclopentane-1S,3R-dicarboxylic acid (trans-ACPD), which was much greater in brain slices from 8-day-old rats and was nearly absent in the adult cerebellum and olfactory bulb, where we have found the highest levels of mRNA. In addition, mGluR mRNA was detectable in cultured cerebellar granule cells but not in cultured neurons from cerebral hemispheres or in cultured astrocytes, which responded to trans-ACPD with an increased formation of [3H]inositol monophosphate. The discrepancies between levels of mGluR mRNA detected with the pmGR1 probe and trans-ACPD-stimulated polyphosphoinositide hydrolysis suggest either that different subtypes of mGluRs exist or that mRNA levels are not critical for the dynamic changes in the activity of mGluRs during development.
Insights
Metabotropic glutamate receptor (mGluR) mRNA levels change during rat development, with distinct patterns in different brain regions. These mRNA levels do not correlate with receptor activity, suggesting complex regulation.
Area of Science:
- Neuroscience
- Molecular Biology
- Developmental Biology
Background:
- Metabotropic glutamate receptors (mGluRs) are crucial for synaptic plasticity and neurotransmission.
- Understanding the developmental expression of mGluRs is key to deciphering their role in brain maturation.
- Previous studies have indicated regional and temporal variations in mGluR function.
Purpose of the Study:
- To investigate the developmental expression patterns of metabotropic glutamate receptor (mGluR) mRNA in the rat brain.
- To examine the correlation between mGluR mRNA levels and the functional activity of these receptors during postnatal development.
- To identify specific cell types expressing mGluR mRNA in the developing brain.
Main Methods:
- Northern blot analysis using a specific cDNA probe (pmGR1) to quantify mGluR mRNA levels.
- Measurement of polyphosphoinositide hydrolysis stimulated by trans-ACPD in brain slices and cultured cells.
- Analysis of mGluR mRNA expression in cultured cerebellar granule cells, cerebral neurons, and astrocytes.
Main Results:
- mGluR mRNA levels were highest in the hypothalamus and olfactory bulb in 1-day-old rats, decreasing in other regions like the hippocampus and cerebral cortex.
- mRNA levels increased with age in the cerebellum and hippocampus, while remaining constant in the olfactory bulb, hypothalamus, and cerebral cortex.
- No correlation was found between mGluR mRNA levels and trans-ACPD-stimulated polyphosphoinositide hydrolysis, with activity peaking at 8 days and declining in adults.
Conclusions:
- Developmental expression of mGluR mRNA shows distinct regional and temporal profiles in the rat brain.
- Discrepancies between mRNA levels and receptor activity suggest the existence of different mGluR subtypes or post-transcriptional regulation.
- mRNA levels alone may not determine the dynamic changes in mGluR activity during brain development.