Cholinergic responses in developing outer hair cells of the rat cochlea.
Acetylcholine-evoked currents were investigated using the conventional whole-cell patch-clamp recording technique in developing outer hair cells (OHCs). The cells were isolated from the rat cochlea at different stages of postnatal development ranging from day 4 (P4) to P30. Acetylcholine-evoked currents could be recorded at P6 and P8. At this developmental stage, the majority of OHCs displayed inward nicotinic-like currents near the resting membrane potential. These cholinergic currents zeroed near 0 mV, as expected for a non-selective cation current, and could be reversibly blocked by d-tubocurarine. At P12 and adult stage, the cholinergic response of OHCs switched to an outward current reversing near EK and displaying a bell shape peaking between -40 and -30 mV. This change in polarity of the acetylcholine response during postnatal development might be explained by progressive functional coupling between acetylcholine ionotropic receptors permeable to Ca2+ and nearby Ca(2+)-activated K+ channels at the synaptic pole of OHCs.
Dulon
D
D
Laboratoire d'Audiologie Expérimentale, INSERM et Université de Bordeaux II, Hôpital Pellegrin, France.
Lenoir
M
M
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D004525:Efferent Pathways / Q000187:drug effects; D005071:Evoked Potentials / Q000187:drug effects; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects* / Q000254:growth & development; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000187:drug effects*
D000109:Acetylcholine