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Ca 2+ Mobilized by Caffeine from the Inositol 1,4,5‐Trisphosphate‐Insensitive Pool of Ca 2+ in Somatic Regions of Sympathetic Neurons Does Not Evoke [ 3 H]Norepinephrine Release
Author(s) -
Wakade Taruna D.,
Bhave Sanjiv V.,
Bhave Anjali,
Przywara Dennis A.,
Wakade Arun R.
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.tb04972.x
Subject(s) - caffeine , stimulation , inositol , endocrinology , muscarinic acetylcholine receptor , medicine , chemistry , inositol phosphate , serotonergic , receptor , biophysics , biology , serotonin , biochemistry
Abstract: The effects of electrical stimulation, muscarinic and serotonergic agonists, and caffeine on [ 3 H]inositol 1,4,5‐trisphosphate ([ 3 H]Ins(1,4,5)P 3 ) content, intracellular free Ca 2+ concentration ([Ca 2+ ] i ), and release of [ 3 H]norepinephrine ([ 3 H]NE) were studied in cultured sympathetic neurons. Neuronal cell body [Ca 2+ ] i was unaffected by muscarinic or serotonergic receptor stimulation, which significantly increased [ 3 H]Ins(1,4,5)P 3 content. Stimulation at 2 Hz and caffeine had no effect on [ 3 H]Ins(1,4,5)P 3 , but caused greater than two‐fold increase in [Ca 2+ ] i . Only 2‐Hz stimulation released [ 3 H]NE. Caffeine had no effect on the release. When [Ca 2+ ] i was measured in growth cones, only electrical stimulation produced an increase in [Ca 2+ ] i . The other agents had no effect on Ca 2+ at the terminal regions of the neurons. We conclude that Ins(1,4,5)P 3 ‐insensitive, but caffeine‐sensitive Ca 2+ stores in sympathetic neurons are located only in the cell body and are not coupled to [ 3 H]NE release.