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Intracellular Ca 2+ Stores Regulate Muscarinic Receptor Stimulation of Phospholipase C in Cerebellar Granule Cells
Author(s) -
Masgrau Roser,
Servitja JoanMarc,
Sarri Elisabet,
Young Kenneth W.,
Nahorski Stefan R.,
Picatoste Fernando
Publication year - 2000
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2000.740818.x
Subject(s) - muscarinic acetylcholine receptor , stimulation , chemistry , intracellular , microbiology and biotechnology , granule cell , granule (geology) , neuroscience , cerebellum , receptor , biophysics , endocrinology , biology , central nervous system , biochemistry , paleontology , dentate gyrus
Muscarinic receptor activation of phosphoinositide phospholipase C (PLC) has been examined in rat cerebellar granule cells under conditions that modify intracellular Ca 2+ stores. Exposure of cells to medium devoid of Ca 2+ for various times reduced carbachol stimulation of PLC with a substantial loss (88%) seen at 30 min. A progressive recovery of responses was observed following the reexposure of cells to Ca 2+ ‐containing medium (1.3 m M ). However, these changes did not appear to result exclusively from changes in the cytosolic Ca 2+ concentration ([Ca 2+ ] i ), which decreased to a lower steady level (∼25 n M decrease in 1‐3 min after extracellular omission) and rapidly returned (within 1 min) to control values when extracellular Ca 2+ was restored. Only after loading of the intracellular Ca 2+ stores through a transient 1‐min depolarization of cerebellar granule cells with 40 m M KCl, followed by washing in nondepolarizing buffer, was carbachol able to mobilize intracellular Ca 2+ . However, the same treatment resulted in an 80% enhancement of carbachol activation of PLC. In other experiments, partial depletion of the Ca 2+ stores by pretreatment of cells with thapsigargin and caffeine resulted in an inhibition (18 and 52%, respectively) of the PLC response. Furthermore, chelation of cytosolic Ca 2+ with BAPTA/AM did not influence muscarinic activation of PLC in either the control or predepolarized cells. These conditions, however, inhibited both the increase in [Ca 2+ ] i and the PLC activation elicited by 40 m M KCl and abolished carbachol‐induced intracellular Ca 2+ release in predepolarized cells. Overall, these results suggest that muscarinic receptor activation of PLC in cerebellar granule cells can be modulated by changes in the loading state of the Ca 2+ stores.