In:
Journal of Neurophysiology, American Physiological Society, Vol. 96, No. 5 ( 2006-11), p. 2342-2353
Abstract:
The Ca 2+ -dependent slow afterhyperpolarization (AHP) is an important determinant of neuronal excitability. Although it is established that modest changes in extracellular pH (pH o ) modulate the slow AHP, the relative contributions of changes in the priming Ca 2+ signal and intracellular pH (pH i ) to this effect remain poorly defined. To gain a better understanding of the modulation of the slow AHP by changes in pH o , we performed simultaneous recordings of intracellular free calcium concentration ([Ca 2+ ] i ), pH i , and the slow AHP in cultured rat hippocampal neurons coloaded with the Ca 2+ - and pH-sensitive fluorophores fura-2 and SNARF-5F, respectively, and whole cell patch-clamped using the perforated patch technique. Decreasing pH o from 7.2 to 6.5 lowered pH i , reduced the magnitude of depolarization-evoked [Ca 2+ ] i transients, and inhibited the subsequent slow AHP; opposite effects were observed when pH o was increased from 7.2 to 7.5. Although decreases and increases in pH i (at a constant pH o ) reduced and augmented, respectively, the slow AHP in the absence of marked changes in preceding [Ca 2+ ] i transients, the inhibition of the slow AHP by decreases in pH o was correlated with low pH o -dependent reductions in [Ca 2+ ] i transients rather than the decreases in pH i that accompanied the decreases in pH o . In contrast, high pH o -induced increases in the slow AHP were correlated with the accompanying increases in pH i rather than high pH o -dependent increases in [Ca 2+ ] i transients. The results indicate that changes in pH o modulate the slow AHP in a manner that depends on the direction of the pH o change and substantiate a role for changes in pH i in modulating the slow AHP during changes in pH o .
Type of Medium:
Online Resource
ISSN:
0022-3077
,
1522-1598
DOI:
10.1152/jn.01269.2005
RVK:
XA 10000 ; XA 552555
Language:
English
Publisher:
American Physiological Society
Publication Date:
2006
detail.hit.zdb_id:
80161-6
detail.hit.zdb_id:
1467889-5
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