Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCB288

Poster Communications

Distinct functional roles for different types of calcium channels in facilitation at mossy fiber to CA3 pyramidal cell synapses

S. Chamberland1, A. Evstratova1, K. Toth1

1. Universite Laval, Quebec City, Quebec, Canada.

Neurotransmitter release from presynaptic terminal is ensured by calcium entering through several types of VGCCs. Although the spatial distribution of distinct VGCCs impacts calcium dynamics and neurotransmitter release, the specific contribution of individual types of VGCCs to neurotransmitter release remains poorly defined. To dissect the roles of P/Q and N-types VGCCs, we used random-access two-photon calcium imaging, electrophysiology and electron microscopy. Our results show that P/Q- and N-types VGCCs support different calcium dynamics with specialized functions in triggering neurotransmitter release. First, bouton calcium imaging revealed that P/Q-type VGCCs contributed a larger but more spatially homogeneous fraction of calcium than N-type VGCCs. Consistent with a global calcium increase, blockade of P/Q-type VGCCs prevented the recruitment of additional release sites during trains of activity. This effect could be mimicked by EGTA-AM, indicating that P/Q-type VGCCs can be loosely-coupled to the sensor. In contrast, antagonizing N-type VGCCs decreased the overall amplitude of EPSCs but had no effect on short-term facilitation. Altogether, our results demonstrate the highly specialized roles of P/Q- and N-type VGCCs in neurotransmitter release. While N-type VGCCs are tightly-coupled to calcium sensor and provide local calcium elevations, P/Q-type VGCCs are well-suited to support global calcium elevations and promote the recruitment of additional release sites during trains of activity.

Where applicable, experiments conform with Society ethical requirements