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Rapid modulatory effect of estradiol on acetylcholine‐induced Ca 2+ signal is mediated through cyclic‐GMP cascade in LHRH‐releasing GT1‐7 cells
Author(s) -
Morales Araceli,
Díaz Mario,
Guelmes Pedro,
Marín Raquel,
Alonso Rafael
Publication year - 2005
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2005.04432.x
Subject(s) - acetylcholine , cascade , cyclic gmp , chemistry , medicine , endocrinology , biophysics , biology , nitric oxide , chromatography
Hypothalamic luteinizing hormone‐releasing hormone neurons (LHRH) form the final pathway for the central control of reproduction through the release of LHRH into the pituitary‐hypothalamic system. We previously found that LHRH‐producing GT1‐7 cells respond to acetylcholine (ACh) with an increase in intracellular calcium ([Ca 2+ ] i ) through activation of muscarinic receptors. This effect is acutely modulated by 17β‐estradiol in a manner compatible with specific membrane binding sites. Because increasing evidence suggests that second messengers are involved in the rapid action of estradiol, the aim of the present study was to identify the pathway underlying estrogen actions on ACh‐induced Ca 2+ signals. 8‐Bromoguanosine 3′,5′‐cyclic monophosphate (10 µ m ) and C‐type natriuretic peptide (10 µ m ) mimicked the effect of estradiol. On the contrary, neither dibutyryl cAMP (100 µ m ), forskolin (100 n m or 10 µ m ), or sodium nitroprusside (10 µ m ) induced any modification of [Ca 2+ ] i in response to ACh. The effect of estradiol on calcium transients was totally blocked by two different cGMP‐dependent protein kinase (PKG) inhibitors. In addition, phosphorylation of inositol 1,4,5‐triphosphate (IP 3 ) receptor was rapidly induced by estradiol but totally blocked when the cells were pretreated with a PKG inhibitor. We conclude that physiological concentrations of estradiol reduce ACh‐induced Ca 2+ transients via a mechanism involving a membrane‐associated guanylate cyclase, which finally induces a PKG‐dependent IP 3 receptor phosphorylation that modifies calcium release from the endoplasmic reticulum.