Presynaptic CaV2.1 calcium dependent facilitation is essential for faithful auditory information transfer

Abstract

Activity-dependent modulation of presynaptic voltage-gated Ca2+ channels (CaV2) regulates Ca2+ influx to control neuronal circuit output. Although CaV2.1 can undergo robust Ca2+ dependent facilitation (CDF), whether it occurs in native central nervous system neuronal circuits is disputed. Accurate auditory information processing requires precise and reliable synaptic transmission at high activity rates in the auditory brainstem. To determine if CaV2.1 CDF is a key regulator of high-fidelity synaptic transmission, we expressed CaV2.1 splice variants capable (CaV2.1 37a) or incapable (CaV2.1 37b) of CDF at the calyx of Held presynaptic terminal in the auditory brainstem. We found no difference in basal CaV2.1 currents or synaptic transmission. However, CaV2.1 37b terminals lacked CDF, synaptic facilitation and had a decreased reliability and precision of postsynaptic action-potential firing. Additionally, the Wave III amplitude of the auditory brainstem responses was reduced. We propose that CaV2.1 CDF is essential for accurate auditory information processing.