Activity-dependent compartmentalized regulation of dendritic Ca2+ signaling in hippocampal interneurons.

Activity-dependent regulation of synaptic inputs in neurons is controlled by highly compartmentalized and dynamic dendritic calcium signaling. Among multiple Ca(2+) mechanisms operating in neuronal dendrites, voltage-sensitive Ca(2+) channels (VSCCs) represent a major source of Ca(2+) influx; however, their use-dependent implication, regulation, and function in different types of central neurons remain widely unknown. Using two-photon microscopy to probe Ca(2+) signaling in dendrites of hippocampal oriens/alveus interneurons, we found that intense synaptic activity or local activation of mGluR5 induced long-lasting potentiation of action potential evoked Ca(2+) transients. This potentiation of dendritic Ca(2+) signaling required mGluR5-induced intracellular Ca(2+) release and PKC activation and was expressed as a selective compartmentalized potentiation of L-type VSCCs. Thus, in addition to mGluR1a-dependent synaptic plasticity, hippocampal interneurons in the feedback inhibitory circuit demonstrate a novel form of mGluR5-induced dendritic plasticity. Given an implication of L-type VSCCs in the induction of Hebbian LTP at interneuron excitatory synapses, their activity-dependent regulation may represent a powerful mechanism for regulating synaptic plasticity.