Glutamate receptor-mediated calcium responses in acutely isolated hippocampal astrocytes.
GFAP(+) cells were acutely isolated from the hippocampi of 1-10 day old rats, and the intracellular calcium responses to L-glutamate, ATP, and 5-HT were studied in single cells. Eighty-two percent of such cells responded to glutamate, 20% of them responded to ATP, and none responded to 5-HT. The same cells that failed to respond to ATP and 5-HT often responded to glutamate. These proportions of cells responding to glutamate and ATP are very similar to those reported for GFAP(+) astrocytes in hippocampal slices (Porter and McCarthy, 1995a,b). After culturing for 1-2 days in serum-containing medium, 60% of such acutely isolated cells responded to either glutamate or ATP, and 5% to 5-HT. After 1 week in culture, the percentage of cells responding to glutamate remained essentially the same (62%) but the percentages of cells responding to ATP and 5-HT increased to 92% and 62%, respectively. These percentages were very close to the results obtained from primary hippocampal astrocyte cultures prepared from 1 day old rats and cultured for 1-2 weeks in vitro. Pharmacological characterization showed that the Ca2+ responses of acutely isolated hippocampal astrocytes from P1-10 rats was due to activation of a group I metabotropic glutamate receptor. The calcium responses to ATP and 5-HT in acutely isolated cells that were then cultured were mediated by P2y and 5-HT2A receptors, respectively. These data show that, like cortical astrocytes (Kimelberg et al., 1997), GFAP(+) astrocytes cultured from the hippocampi of young rats showed marked differences in receptor expression compared to their acutely isolated counterparts. Also, since the astrocytes acutely isolated from these 2 different brain regions showed qualitatively the same responses for the 3 receptors selected, it indicates a degree of homogeneity of receptor expression for astrocytes from these 2 brain regions.
Cai
Z
Z
Department of Pharmacology and Neuroscience, Albany Medical College, New York 12208, USA.
Kimelberg
H K
HK
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003952:Diagnostic Imaging; D004594:Electrophysiology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism
D005904:Glial Fibrillary Acidic Protein; D011500:Protein Synthesis Inhibitors; D017470:Receptors, Glutamate; D012701:Serotonin; D000255:Adenosine Triphosphate; D003513:Cycloheximide; D002118:Calcium