Differentially distributed IP3 receptors and Ca2+ signaling in rod bipolar cells.
OBJECTIVE
Inositol (1,4,5)-trisphosphate receptors (IP3Rs) contribute substantially to cytosolic free calcium ion (Ca2+) concentration transients and thereby modulate neuronal function. The present study was undertaken to determine the contribution of IP3Rs to the function of rod bipolar cells in the retina.


METHODS
Immunoreactivity for IP3Rs in rod bipolar cells from mouse retinas was detected by immunocytochemical methods. Intracellular Ca2+ concentrations were optically recorded in acutely isolated rod bipolar cells, and biophysical properties of IP3Rs were analyzed with single channel electrophysiology.


RESULTS
The distribution of IP3R isoforms was correlated with cytosolic Ca2+ transients induced by activation of group I metabotropic glutamate receptors (mGluRs) and with biophysical properties of differentially expressed IP3Rs.


CONCLUSIONS
The differential distribution of IP3Rs is used by rod bipolar cells to convey Ca2+ signals that are distinct in their duration, amplitude, and kinetics at the subcellular level, and that serve the functions of individual subcellular compartments. IP3R-mediated Ca2+ signaling indicates a potential mechanism for the adaptation of the ON-pathway of vision and for coincidence and threshold detection in retinal neurons.
Koulen
Peter
P
Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas 76107-2699, USA. pkoulen@hsc.unt.edu
Wei
Jiao
J
Madry
Christian
C
Liu
Jiyuan
J
Nixon
Everett
E
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D004594:Electrophysiology; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007395:Interneurons / Q000378:metabolism*; D051379:Mice; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology*
D015220:Calcium Channels; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D018094:Receptors, Metabotropic Glutamate; D002118:Calcium