Associative Plasticity at Excitatory Synapses Facilitates Recruitment of Fast-Spiking Interneurons in the Dentate Gyrus

Sambandan, S., Sauer, J.-F., Vida, I. and Bartos, M. (2010) Associative Plasticity at Excitatory Synapses Facilitates Recruitment of Fast-Spiking Interneurons in the Dentate Gyrus. Journal of Neuroscience, 30(35), pp. 11826-11837. (doi: 10.1523/JNEUROSCI.2012-10.2010)

Abstract

Fast-spiking perisomatic-inhibitory interneurons (PIIs) receive convergent excitation and mediate both feedforward and feedback inhibition in cortical microcircuits. However, it remains poorly understood how convergent excitatory inputs recruit PIIs to produce precisely timed inhibition. Here, we analyzed the interaction of inputs from the entorhinal cortex [perforant path (PP)] and from local granule cells [mossy fibers (MFs)] onto PIIs in the rat dentate gyrus (DG). PP stimulation alone activates PIIs with low temporal precision. Interestingly, when PP and MFs are coactivated with a 10 ms delay, PIIs discharge with precise timing. Moreover, repeated coactivation of the two inputs induces associative long-term potentiation (LTP) at MF synapses. Under these conditions, a single potentiated MF input is sufficient to recruit PIIs in a reliable and highly precise manner to provide feedback inhibition. MF-LTP depends on the discharge of PIIs, indicating Hebbian plasticity. However, MF-LTP is preserved when NMDA receptors are blocked but depends on transmission through Ca2+-permeable AMPA receptors (AMPARs). PP-PII synapses, in contrast, lack Ca2+-permeable AMPARs and do not show plasticity on associative activation. Thus, precise recruitment of PIIs requires excitation through MF-PII synapses during feedforward activation. We propose that associative plasticity at these synapses is a central mechanism that adjusts inhibition levels to maintain sparse activity and to improve signal-to-noise ratio in the DG network.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Vida, Dr Imre
• Authors: Sambandan, S., Sauer, J.-F., Vida, I., and Bartos, M.
• College/School: College of Medical Veterinary and Life Sciences > School of Life Sciences
• Journal Name: Journal of Neuroscience
• ISSN: 0270-6474