Sodium and calcium currents shape action potentials in immature mouse inner hair cells

• DOI: 10.1113/jphysiol.2003.043612
• Publication Date: 2003-08-26T00:49:10Z
• Authors: Walter Marcotti; Stuart L. Johnson; Alfons Rüsch; Corné J. Kros
• Keywords: 0301 basic medicine; Aging; Hair Cells, Auditory, Inner; Electric Conductivity; Action Potentials; Mice, Inbred Strains; Exocytosis; Sodium Channels; Mice; 03 medical and health sciences; Animals, Newborn; Reaction Time; Animals; Calcium; Calcium Channels

Before the onset of hearing at postnatal day 12, mouse inner hair cells (IHCs) produce spontaneous and evoked action potentials. These spikes are likely to induce neurotransmitter release onto auditory nerve fibres. Since immature IHCs express both alpha1D (Cav1.3) Ca2+ Na+ currents that activate near resting potential, we examined whether these two conductances involved in shaping Both had extremely rapid activation kinetics, followed by fast complete voltage-dependent inactivation for current, slower, partially Ca2+-dependent current. Only current is necessary induced potentials, 29 % lacked a The does, however, shorten time reach action-potential threshold, whereas mainly involved, together with K+ currents, determining speed size spikes. increased up end first week. After this, reduced about 30 its maximum persisted mature IHCs. was downregulated around hearing, when spiking also known disappear. Although observed as early embryonic 16.5, role generation only evident from just after birth, membrane potential became sufficiently negative remove sizeable fraction (half -71 mV). positively correlated developmental change frequency.