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Modulation of Ca 2+ ‐dependent currents in metabolically stressed cultured sensory neurones by intracellular photorelease of ATP
Author(s) -
Stapleton S.R.,
Bell B.A.,
Wootton J.F.,
Scott R.H.
Publication year - 1995
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1995.tb13261.x
Subject(s) - intracellular , biophysics , chemistry , adenosine , depolarization , biochemistry , adenosine triphosphate , biology
1 The whole cell recording technique was used to study high voltage‐activated Ca 2+ currents and Ca 2+ ‐activated Cl − tail currents from cultured neonatal dorsal root ganglion neurones of the rat which were metabolically stressed. The neurones were metabolically stressed with 2‐deoxy‐ d ‐glucose (5 m m ) for 30 min to 3 h. The aim of the project was to examine the actions of intracellular photorelease of ATP on the properties of Ca 2+ ‐dependent currents and determine if the effects of metabolic stress could be reversed. 2 The mean duration of Ca 2+ ‐activated Cl − tail currents was significantly increased by metabolic stress and this effect was reversed by intracellular photorelease of approximately 300 μ m ATP. Intracellular photolysis of ‘caged’ photolabile compounds was achieved with a xenon flash lamp. 3 Intracellular photorelease of ATP and adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) (about 40 μ m ) also accelerated the inactivation of high voltage‐activated Ca 2+ currents evoked by 500 ms depolarizing step commands from −90 mV to 0 mV. This effect was prevented by intracellular application of the calcineurin (protein phosphatase‐2B) inhibitor cyclosporin A (14 n m ) and cyclophihn A (50 n m ) either applied together or individually. In contrast the protein phosphatase 1 and 2A inhibitor, calyculin A, increased voltage‐activated Ca 2+ currents, but failed to prevent enhanced inactivation induced by intracellular photorelease of ATP. Intracellular photorelease of ATP had no effect on Ca 2+ currents recorded from control neurones which were not metabolically stressed and supplied with glucose and ATP in the extracellular and patch pipette solutions respectively. 4 In conclusion, intracellular photorelease of ATP increases the decay of Ca 2+ ‐activated Cl − tail currents in metabolically stressed neurones suggesting that the efficiency of intracellular Ca 2+ buffering was improved. Additionally, an ATP/cyclic AMP‐dependent component of high voltage‐activated Ca 2+ current inactivation which is mediated by calcineurin is revealed following photolysis of ‘caged’ ATP or cyclic AMP in metabolically stressed neurones.