Associative synaptic plasticity in GABAergic interneurons of the rat dentate gyrus

The dentate gyrus (DG) is a sub-region of the hippocampus which is important for memory formation and storage in the brain. It comprises two major classes of neurons called granule cells (GCs), the local principal cells and the interneurons which receive sensory information from the entorhinal cortex (EC). The GCs contain glutamate as neurotransmitter and excite the postsynaptic cells whereas the interneurons release GABA and inhibit the target cells. While the GCs are abundant in number and transmit the processed information to CA3 via mossy fibres (MFs), the interneurons determine when and where the information flows through the principal cell network. To understand how information is processed in DG, it is paramount to understand the role of interneurons in the network in detail. Moreover, disruption of this basal transmission set-up forms the basis of many neurological disorders. For example, reduced inhibition on GCs is implicated in epilepsy. Treatment/prevention of such diseases also necessitates better understanding of the role of inhibition in DG. While greater degree of knowledge exists on how interneurons inhibit GCs, how they are activated by afferent inputs is not clear. Hence, the present work is primarily focussed on studying the physiology behind synaptic activation of interneurons by afferent excitatory inputs in DG. The results obtained might help in studying the causes of pathological conditions of DG in addition to elucidating the circuit mechanisms of information processing.