Calcium responses mediated by type 2 IP3-receptors are required for osmotic volume regulation of retinal glial cells in mice.
Prevention of osmotic swelling of retinal glial (Müller) cells is required to avoid detrimental decreases in the extracellular space volume during intense neuronal activity. Here, we show that glial cells in slices of the wildtype mouse retina maintain the volume of their somata constant up to approximately 4 min of perfusion with a hypoosmolar solution. However, calcium chelation with BAPTA/AM induced a rapid swelling of glial cell bodies. In glial cells of retinas from inositol-1,4,5-trisphosphate-receptor type 2-deficient (IP(3)R2(-/-)) mice, hypotonic conditions caused swelling of the cell bodies without delay. Exogenous ATP (acting at P2Y(1) receptors) prevented the swelling of glial cells in retinal slices from wildtype but not from IP(3)R2(-/-) mice. Müller cells from IP(3)R2(-/-) mice displayed a strongly reduced amplitude of the ATP-evoked calcium responses as compared to cells from wildtype mice. It is concluded that endogenous calcium signaling mediated by IP(3)R2 is required for the osmotic volume regulation of retinal glial cells.
Paul Flechsig Institute of Brain Research, University of Leipzig, 04109 Leipzig, Germany.
Stephan
S
Lipp
Antje
A
Wurm
Thomas
T
Pannicke
Peter
P
Wiedemann
Andreas
A
Reichenbach
Ju
J
Chen
Andreas
A
Bringmann
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D048429:Cell Size; D007038:Hypotonic Solutions; D007150:Immunohistochemistry; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009457:Neuroglia / Q000378:metabolism*; D009924:Organ Culture Techniques; D009995:Osmosis / Q000502:physiology; D012160:Retina / Q000166:cytology / Q000378:metabolism*
D007038:Hypotonic Solutions; D053496:Inositol 1,4,5-Trisphosphate Receptors; D000255:Adenosine Triphosphate