Premium
Stimulation of Muscarinic Acetylcholine Receptors Increases Synaptosomal Free Calcium Concentration by Protein Kinase‐Dependent Opening of L‐Type Calcium Channels
Author(s) -
Boess Frank G.,
Balasubramanian M. K.,
Brammer Michael J.,
Campbell Iain C.
Publication year - 1990
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 - 10.1111/j.1471-4159.1990.tb08843.x
Subject(s) - carbachol , muscarinic acetylcholine receptor , chemistry , calcium , endocrinology , acetylcholine , protein kinase c , medicine , hexamethonium , synaptosome , stimulation , calcium channel blocker , biophysics , biology , biochemistry , receptor , kinase , organic chemistry
In synaptosomes prepared from rat cerebral cortex, free cytosolic calcium concentration ([Ca 2+ ] i ) was measured using the fluorescent dye fura‐2, Incubation of fura‐2‐loaded synaptosomes with carbachol increased [Ca 2+ ] i in a dose‐dependent manner (1–1,000 μ M ), with a maximum response of 22 × 2% at approximately 100 μ M and an EC 50 (calculated concentration producing 50% of the maximum response) of 30 μ M The effect of carbachol (100 μ M ) on [Ca 2+ ], was antagonised by atropine, but not by hexamethonium (10 μ M ). The calculated concentration of atropine needed for 50% inhibition (IC 50 ) was 260 n M. The rise in [Ca 2+ ] i produced by carbachol was reduced in the absence of extrasynaptosomal Ca 2+ and effectively blocked by the L‐type calcium channel blocker nifedipine (with an IC 50 of 29 n M ). The response to carbachol was reduced if the synaptosomes were preincubated with the protein kinase inhibitors H7 [1‐(5‐isoquinolinylsulfonyl)‐2‐methylpiperazine] (from 17% in the solvent control to 4%) and staurosporine (from 20% in the solvent control to 3%). These results show that stimulation of muscarinic acetylcholine receptors in synaptosomes increases [Ca 2+ ] i by protein kinase‐dependent activation of 1,4‐dihydropyridinesensitive calcium channels.