ISSN:
1432-1017
Keywords:
Neurones
;
Ca2+ channels
;
Temperature
;
Patch-clamp
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract The temperature dependence of high voltage activated Ca2+ channels has been investigated in cultured dorsal root ganglion neurones from chick embryos, using the cell-attached patch-clamp technique. The dihydropyridine sensitive L-type Ca2+ channel had a conductance of 23 pS, with 110 mM Ba2+ as charge carrier and in the presence of 3 μM Bay K 8644. When the temperature was raised from 15 to 30 °C, the unitary channel current amplitude increased, with Q10 value equal to 1.4. The rising phase of the averaged single-channel current became faster, with Q10 value 2.7, whereas the decay phase showed a lower temperature sensitivity. Channel open probability decreased according to an exponential distribution of open and closed times. A second type of Ca2+ channel was identified, which was DHP-insensitive and had a lower conductance with a mean value equal to 13 pS. For the current amplitude, the Q10 value was 1.3. Both activation and inactivation kinetics were strongly accelerated by an increase in temperature. The corresponding time constants gave Q10 values equal to 5.9 for activation, and 2.0 for inactivation. Peak channel open probability was highly sensitive to a change in temperature, with a Q10 value of 1.6. Finally, in ω-conotoxin GVIA pre-treated neurones, a non-inactivating DHP-insensitive Ca2+ channel with the lowest unitary conductance (10 pS) and a much lower temperature dependence was recorded. Single-channel current was increased by heating, with Q10 value 1.3, whereas the channel kinetics were almost unaffected by temperature. Our data are consistent with the assumption that the different temperature dependence of the Ca2+ channel behaviours may be explained by separate gating processes of three types of Ca2+ channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01007610
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