Metabotropic glutamate receptors in acutely isolated hippocampal astrocytes: Developmental changes of mGluR5 mRNA and functional expression

✍ Scribed by Zhaohui Cai; Gary P. Schools; Harold K. Kimelberg

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 347 KB
• Volume: 29
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/(sici)1098-1136(20000101)29:1<70::aid-glia7>3.0.co;2-v

✦ Synopsis

We previously found that 82% of glial fibrillary acidic protein (GFAP)positive hippocampal astrocytes acutely isolated from P1-10 rats responded to glutamate (Glu) with transient intracellular calcium increases via activation of a Group I metabotropic glutamate receptor (mGluR). Fewer cells responded to ATP and none to serotonin (5-HT). In this study we asked the question whether hippocampal astrocytes in older animals retain this relative pattern of expression. We have found that 77% of GFAP (ϩ) cells from P11-20 rats responded to 50 µM Glu, 43% to ATP, and none to 5-HT. Thirty-three percent of GFAP (ϩ) cells from P25-35 rats responded to Glu, 12% to ATP and 3% to 5-HT. In the case of the responses to Glu, pharmacological characterization and single-cell RT-PCR data confirmed that these responses were mediated by the mGluR5 subtype of group I mGluRs. Also, fewer (36%) GFAP mRNA (ϩ) cells from P25-35 rats expressed detectable mGluR5 mRNA than those from P11-20 rats (77%). This number essentially corresponds to the number of GFAP(ϩ) showing a Ca 2ϩ response to Glu. Both mGluR5a and b were expressed with equal frequency in cells from P11-20 rats, but the b form predominated in cells from older animals. Overall, our studies show that expression of mGluR5 in hippocampal astrocytes decreases with increasing age and the ''a'' splice variant declines to a greater extent than the ''b'' splice variant, corresponding to the developmental changes shown in total tissue for mGluR5.