Featured Finding Figure
The Cav2.1 (P/Q-) and Cav2.2 (N-type) voltage-gated calcium channels (VGCCs) play a predominant role in neurotransmitter release at central synapses, but their distribution is not uniform across different types of synapses. Although the functional significance of the differential distribution of N-type and P/Q-type VGCCs is poorly understood, distinct types of VGCCs appear to differentially affect synaptic properties. For example, P/Q-type VGCCs are located closer to release sites and are less affected by G-protein-mediated inhibition than are N-type VGCCs. Thus, P/Q-type VGCCs might be beneficial at synapses with high probability of release and precise timing of neurotransmission, such as the inhibitory inputs from parvalbumin-containing fastspiking interneurons (FSIs) to pyramidal cells (PCs) in the neocortex. To determine whether VGCCs types predominate at synapses from FSIs to PCs in rat prefrontal cortex, whole-cell paired recordings combined with intracellular labeling with biocytin and fluorescence immunohistochemistry for parvalbumin were performed in acute slices (top panel of figure). Bath application of the specific N-type VGCC blocker -conotoxin-GVIa (1 M) did not alter IPSP amplitude, failure rate or synaptic dynamics; in contrast, application of P/Q-type VGCC blocker -agatoxin-IVa (0.5 M) completely and irreversibly blocked neurotransmission (bottom panel of figure). These results indicate that P/Q-type VGCCs mediate the GABA release from parvalbumin-positive FSIs to PCs in the rat neocortex.
Zaitsev AV, Povysheva NV, Lewis DA, Krimer LS: P/Q-type, but N-type Ca2+ channels mediate GABA release from fast-spiking interneurons to pyramidal cells in rat prefrontal cortex. J Neurophysiology 97: 3567-3573, 2007.

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David A. Lewis, M.D. | Department of Psychiatry | University of Pittsburgh
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