Functional compartmentalisation and regulation of postsynaptic Ca2+ transients in inhibitory interneurons

Information processing within neural circuits depends largely on the dynamic interactions between the principal cells and inhibitory interneurons. It is further determined by the efficacy of synaptic transmission between individual circuit elements, which is in turn tightly regulated by changes in network activity to allow for numerous adaptations to occur at a single synapse. Intracellular calcium (Ca2+) is a crucial factor in the regulation of synaptic efficacy in neuronal networks. Evidence from high-resolution imaging studies has revealed the intricacies of how Ca2+ signalling is organised in the dendrites of different cell types. Inhibitory interneurons exhibit a variety of postsynaptic Ca2+ mechanisms, which are recruited by distinct activity patterns and are responsible for the formation of functionally segregated dendritic Ca2+ microdomains. Furthermore, postsynaptic Ca2+ signals in these cells not only contribute to the induction of synaptic plasticity but also may themselves undergo different forms of plastic modifications, depending on the activity level. This compartmentalised regulation of postsynaptic Ca2+ signalling may have a significant impact on the induction of synaptic plasticity and on single-interneuron and network computations.