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Electrically evoked dendritic pH transients in rat cerebellar Purkinje cells
Author(s) -
Willoughby Debbie,
Schwiening Christof J.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.027508
Subject(s) - depolarization , chemistry , biophysics , soma , intracellular ph , extracellular , calcium , biochemistry , neuroscience , biology , organic chemistry
Our aim was to test the hypothesis that depolarization‐induced intracellular pH (pH i ) shifts in restricted regions (dendrites) of mammalian neurones might be larger and faster than those previously reported from the cell soma. We used confocal imaging of the pH‐sensitive dye, HPTS, to measure pH changes in both the soma and dendrites of whole‐cell patch‐clamped rat cerebellar Purkinje cells. In the absence of added CO 2 ‐HCO 3 − , depolarization to +20 mV for 1 s caused large (≈0.14 pH units) and fast dendritic acid shifts, whilst the somatic acidifications were significantly smaller (≈0.06 pH units) and slower. The pH i shifts were smaller in the presence of 5 % CO 2 ‐25 m m HCO 3 − ‐buffered saline (≈0.08 pH units in the dendrites and ≈0.03 pH units in the soma), although a clear spatiotemporal heterogeneity remained. Acetazolamide (50 μM) doubled the size of the dendritic acid shifts in the presence of CO 2 ‐HCO 3 − , indicating carbonic anhydrase activity. Removal of extracellular calcium or addition of the calcium channel blocker lanthanum (0.5 m m ) inhibited the depolarization‐evoked acid shifts. We investigated more physiological pH i changes by evoking modest bursts of action potentials (≈10 s duration) in CO 2 ‐HCO 3 − ‐buffered saline. Such neuronal firing induced an acidification of ≈0.11 pH units in the fine dendritic regions, but only ≈0.03 pH units in the soma. There was considerable variation in the size of the pH i shifts between cells, with dendritic acid shifts as large as 0.2‐0.3 pH units following a 10 s burst of action potentials in some Purkinje cells. We postulate that these large dendritic pH i changes (pH microdomains) might act as important signals in synaptic function.