PT  - JOURNAL ARTICLE
AU  - Olivier Camiré
AU  - Lisa Topolnik
TI  - Dendritic Calcium Nonlinearities Switch the Direction of Synaptic Plasticity in Fast-Spiking Interneurons
AID  - 10.1523/JNEUROSCI.2253-13.2014
DP  - 2014 Mar 12
TA  - The Journal of Neuroscience
PG  - 3864--3877
VI  - 34
IP  - 11
4099  - http://www.jneurosci.org/content/34/11/3864.short
4100  - http://www.jneurosci.org/content/34/11/3864.full
SO  - J. Neurosci.2014 Mar 12; 34
AB  - Postsynaptic calcium (Ca2+) nonlinearities allow neuronal coincidence detection and site-specific plasticity. Whether such events exist in dendrites of interneurons and play a role in regulation of synaptic efficacy remains unknown. Here, we used a combination of whole-cell patch-clamp recordings and two-photon Ca2+ imaging to reveal Ca2+ nonlinearities associated with synaptic integration in dendrites of mouse hippocampal CA1 fast-spiking interneurons. Local stimulation of distal dendritic branches within stratum oriens/alveus elicited fast Ca2+ transients, which showed a steep sigmoidal relationship to stimulus intensity. Supralinear Ca2+ events required Ca2+ entry through AMPA receptors with a subsequent Ca2+ release from internal stores. To investigate the functional significance of supralinear Ca2+ signals, we examined activity-dependent fluctuations in transmission efficacy triggered by Ca2+ signals of different amplitudes at excitatory synapses of interneurons. Subthreshold theta-burst stimulation (TBS) produced small amplitude postsynaptic Ca2+ transients and triggered long-term potentiation. In contrast, the suprathreshold TBS, which was associated with the generation of supralinear Ca2+ events, triggered long-term depression. Blocking group I/II metabotropic glutamate receptors (mGluRs) during suprathreshold TBS resulted in a slight reduction of supralinear Ca2+ events and induction of short-term depression. In contrast, blocking internal stores and supralinear Ca2+ signals during suprathreshold TBS switched the direction of plasticity from depression back to potentiation. These data reveal a novel type of supralinear Ca2+ events at synapses lacking the GluA2 AMPA subtype of glutamate receptors and demonstrate a general mechanism by which Ca2+-permeable AMPA receptors, together with internal stores and mGluRs, control the direction of plasticity at interneuron excitatory synapses.