Altered synaptic synchrony in motor nerve terminals lacking P/Q-calcium channels.

Abstract

The variance in synaptic delays among endplate potentials events (referred here as jitter) was measured to study the contribution of voltage dependent calcium channels to transmission synchronicity in neuromuscular synapses from wild type and alpha-1A knockout mice (i.e., lacking P/Q type calcium channels). Knockout synapses presented higher jitter values than wild type ones under a wide range of extracellular calcium concentration ([Ca2+]o) values. Accordingly, wild type synapses showed less synchronic neurotransmitter release when P/Q type calcium channels were partially blocked as well as under lower [Ca2+]o. In the knockout synapses, N-type calcium channels mediated neurotransmitter release in a more temporally precise way than the R-type ones. Our results suggest that the type of calcium channels mediating transmitter release influenced the degree of synaptic synchrony. Thus, these results provide insight on the mechanisms underlying several pathologies associated with P/Q type calcium channels.