Characterization of acid-sensitive ion channels in freshly isolated rat brain neurons

Transient proton-activated currents induced by rapid shifts of the extracellular pH from 7.4 to ≤6.8 were recorded in different neurons freshly isolated from rat brain (hypoglossal motoneurons, cerebellar Purkinje cells, striatal giant cholinergic interneurons, hippocampal interneurons, CA1 pyramidal neurons and cortical pyramidal neurons) using whole-cell patch clamp technique. Responses of hippocampal CA1 pyramidal neurons were weak (100–300 pA) in contrast to other types of neurons (1–3 nA). Sensitivity of neurons to rapid acidification varied from pH 50 6.4 in hypoglossal motoneurons to 4.9 in hippocampal interneurons. Proton-activated currents were blocked by amiloride (IC 50 varied from 3.6 to 9.5 μM). Reversal potential of the currents was close to E Na, indicating that the currents are carried by sodium ions. The data obtained suggest that the proton-activated currents in the neurons studied are mediated by acid-sensitive ion channels. Strong acidification (pH