Premium
Effects of metabolic blockers on Ca 2+ ‐dependent currents in cultured sensory neurones from neonatal rats
Author(s) -
Stapleton S.R.,
Scott R.H.,
Bell B.A.
Publication year - 1994
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.1476-5381.1994.tb14023.x
Subject(s) - sensory system , neuroscience , chemistry , endocrinology , medicine , biology
1 The whole cell variant of the patch clamp technique was used to record high voltage‐activated Ca 2+ currents and Ca 2+ ‐activated Cl − tail currents from cultured neonatal rat dorsal root ganglion neurones. The aim of the project was to use these currents as physiological indices of intracellular Ca 2+ regulation under control conditions and in the presence of metabolic inhibitors. 2 Carbonyl cyanide p ‐trifluoromethoxyphenylhydrazone (5 μ m ) and sodium cyanide (1 μ m ) inhibited Ca 2+ currents within 20 s, even when ATP was present in the patch pipette solution, suggesting a direct action on Ca 2+ channels. These metabolic inhibitors did not affect Ca 2+ current ‘run down’ or inactivation kinetics. 3 Cultured neonatal dorsal root ganglion neurones of the rat were relatively insensitive to the removal of glucose and ATP from the recording solutions for up to 3 h. These data suggest that the Ca 2+ homeostatic mechanisms in these cells are highly resistant to metabolic insult. 4 However 2‐deoxy‐ d ‐glucose (5 mM) in the extracellular recording medium with no ATP or glucose present did prolong the deactivation time of Ca 2+ ‐activated Cl − tail currents and increase the total charge flow following activation of a 500 ms voltage‐activated Ca 2+ current. This effect was prevented by inclusion of d ‐fructose 1,6‐diphosphate (500 μ m ) in the patch pipette solution. 5 We conclude that some agents used to induce chemical hypoxia, such as carbonyl cyanide p ‐trifluoromethoxyphenylhydrazone and sodium cyanide, may interact directly with voltage‐activated Ca 2+ channels and are therefore not appropriate for use in studying disturbed neuronal Ca 2+ homeostasis. However, the use of 2‐deoxy‐ d ‐glucose in the absence of glucose and ATP does represent a model of disturbed Ca 2+ homeostasis in cultured dorsal root ganglion neurones. In this study we have combined the whole cell recording technique with cultured neurones under conditions which produce a degree of metabolic stress as reflected by prolonged Ca 2+ ‐activated Cl − tail currents. The reduced efficiency of handling of intracellular Ca 2+ loads may be an important factor contributing to the onset of neuronal damage during hypoxia and ischaemia.