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This Article Full Text Full Text (PDF) All Versions of this Article: 581/2/529    most recent jphysiol.2006.125666v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Jonz, M. G. Articles by Barnes, S. Search for Related Content PubMed PubMed Citation Articles by Jonz, M. G. Articles by Barnes, S. Related Collections Neuroscience

¹ Department of Physiology and Biophysics, Dalhousie University, 5859 University Ave, Halifax, NS, B3H 4H7 Canada

Transient changes in extracellular pH (pH_o) occur in the retina and may have profound effects on neurotransmission and visual processing due to the pH sensitivity of ion channels. The present study characterized the effects of acidification on the activity of membrane ion channels in isolated horizontal cells (HCs) of the goldfish retina using whole-cell patch-clamp recording. Currents recorded from HCs were characterized by prominent inward rectification at potentials negative to –80 mV, a negative slope conductance between –70 and –40 mV, a sustained inward current, and outward rectification positive to 40 mV. Inward currents were identified as those of inward rectifier K⁺ (Kir) channels and Ca²⁺ channels by their sensitivity to 10 mM Cs⁺ or 20 µM Cd²⁺, respectively. Both of these currents were reduced when pH_o decreased from 7.8 to 6.8. Glutamate (1 mM)-activated currents were also identified, as were hemichannel currents that were enhanced by removal of extracellular Ca²⁺ and application of 1 mM quinidine. Both glutamate-activated and hemichannel currents were suppressed by a similar reduction of pH_o. When all of these H⁺-inhibited currents were blocked, a small, sustained inward current at –60 mV increased following a decrease in pH_o from 7.8 to 6.8. In addition, slope conductance between –70 and –20 mV increased during this acidification. Suppression of this H⁺-activated current by removal of extracellular Na⁺, and an extrapolated E_rev near E_Na, indicated that this current was carried predominantly by Na⁺ ions.

(Received 27 November 2006; accepted after revision 27 February 2007; first published online 1 March 2007)
Corresponding author M. G. Jonz: Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, K1N 6N5 Canada.  Email: mjonz{at}uottawa.ca