Reduced IP3 sensitivity of IP3 receptor in Purkinje neurons.
The inositol 1,4,5-trisphosphate receptor (IP3R) is highly expressed in Purkinje neurons (PNs) and is thought to be essential for the induction of long-term depression at parallel-fiber-PN synapses. Here, by imaging the fluorescence intensity of the low-affinity Ca2+ indicator inside the Ca2+ stores in the permeabilized single PNs, we analyzed the kinetics of Ca2+ release via the IP3R in controlled cytoplasmic environments. The rate of Ca2+ release is dependent on the IP3 concentration with an EC50 of 25.8 microM, which is > 20-fold greater than that of the IP3R in the isolated preparations or in peripheral cells. This property would be advantageous in inducing the release of Ca2+ in a localized space adjacent to the site of synaptic inputs.
Fujiwara
A
A
Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Japan.
Hirose
K
K
Yamazawa
T
T
Iino
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D003712:Dendrites / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism* / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D051379:Mice; D008813:Mice, Inbred ICR; D011689:Purkinje Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*
D015220:Calcium Channels; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium