{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2023,10,10]],"date-time":"2023-10-10T14:16:08Z","timestamp":1696947368942},"reference-count":16,"publisher":"American Physiological Society","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Neurophysiology"],"published-print":{"date-parts":[[2000,11,1]]},"abstract":"<jats:p> High-voltage\u2013activated calcium currents (HVA) of CA1 neurons are prominently attenuated following a switch from HEPES-buffered solution to one buffered with CO<jats:sub>2<\/jats:sub>\/HCO<jats:sub>3<\/jats:sub> <jats:sup>\u2212<\/jats:sup>. In the present study we investigated whether bicarbonate ions or the dissolved CO<jats:sub>2<\/jats:sub> induce this alteration in current characteristic. The study was carried out on freshly isolated CA1 neurons using the whole cell patch-clamp technique. Maximal calcium conductance and the mean peak amplitude of the currents showed a concentration-dependent decrease when cells were consecutively bathed in solutions containing increasing amounts of bicarbonate and CO<jats:sub>2<\/jats:sub>. This decrease is best described by the Hill equation, yielding a maximal attenuation of 69%, a half-maximal concentration (EC<jats:sub>50<\/jats:sub>) of 7.4 mM HCO<jats:sub>3<\/jats:sub> <jats:sup>\u2212<\/jats:sup>, and a Hill coefficient of 1.8. In parallel, the potentials of half-maximal activation ( V <jats:sub>h,a<\/jats:sub>) and inactivation ( V <jats:sub>h,i<\/jats:sub>) were linearly shifted in hyperpolarizing direction with a maximal shift, in the 10% CO<jats:sub>2<\/jats:sub>\/37 mM HCO<jats:sub>3<\/jats:sub> <jats:sup>\u2212<\/jats:sup> containing solution of 10 \u00b1 1 mV for V <jats:sub>h,a<\/jats:sub>( n = 23) and 17 \u00b1 1.4 mV for V <jats:sub>h,i<\/jats:sub> ( n = 18). When currents were evoked in solutions containing equal concentrations of bicarbonate but different amounts of CO<jats:sub>2<\/jats:sub>, only nonsignificant changes were observed, while marked alterations of the currents were induced when bicarbonate was changed and CO<jats:sub>2<\/jats:sub> held stable. The experiments suggest that bicarbonate is the modulating agent and not CO<jats:sub>2<\/jats:sub>. This bicarbonate-induced modulation may be of critical relevance for the excitation level of the CNS under pathological situation with altered concentration of this ion, such as hyperventilation and metabolic acidosis. <\/jats:p>","DOI":"10.1152\/jn.2000.84.5.2277","type":"journal-article","created":{"date-parts":[[2017,12,21]],"date-time":"2017-12-21T13:51:23Z","timestamp":1513864283000},"page":"2277-2283","source":"Crossref","is-referenced-by-count":5,"title":["Concentration Dependence of Bicarbonate-Induced Calcium Current Modulation"],"prefix":"10.1152","volume":"84","author":[{"given":"C.","family":"Bruehl","sequence":"first","affiliation":[{"name":"Department of Neurology, Heinrich-Heine-University, 40225 Duesseldorf, Germany; and"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"W. 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