Abstract
Using in vitro brain slices of hippocampus and cortex, neuronal oscillations in the frequency range of 30–80 Hz (gamma frequency oscillations) can be induced by a number of pharmacological manipulations. The most routinely used is the bath application of the broad-spectrum glutamate receptor agonist, kainic acid. In the hippocampus, work using transgenic kainate receptor knockout mice have revealed information about the specific subunit composition of the kainate receptor implicated in the generation and maintenance of the gamma frequency oscillation. However, there is a paucity of such detail regarding gamma frequency oscillation in the cortex. Using specific pharmacological agonists and antagonists for the kainate receptor, we have set out to examine the contribution of kainate receptor subtypes to gamma frequency oscillation in the entorhinal cortex. The findings presented demonstrate that in contrast to the hippocampus, kainate receptors containing the GLUK5 subunit are critically important for the generation and maintenance of gamma frequency oscillation in the entorhinal cortex. Future work will concentrate on determining the exact nature of the cellular expression of kainate receptors in the entorhinal cortex.
Highlights
KARs are made up of various combinations of five subunits: GLUK5, GLUK6, GLUK7, KA1, and KA2 [1, 2] which are abundantly expressed in the neocortex [3]
We have demonstrated that GLUK5-containing KARs are important for the maintenance of gamma frequency oscillations in the MEC
The selective activation of GLUK5containing KARs can induce persistent gamma frequency oscillations in the MEC. We demonstrate that it is the specific activation of homomeric GLUK5-containing KARs that is important for the generation of gamma frequency oscillations in the MEC
Summary
KARs are made up of various combinations of five subunits: GLUK5, GLUK6, GLUK7, KA1, and KA2 [1, 2] which are abundantly expressed in the neocortex [3] These subunits make up tetramers of either homomeric or heteromeric assemblies, with GLUK5–7 being able to form functional homomeric receptors [1, 4]. Cortical gamma oscillations are important in higher brain functions, such as learning, memory, and cognition [17,18,19], as well as processing of sensorimotor information [15, 16, 20] In carrying out these functions, cortical gamma oscillations are implicated in various central processes, including long-term potentiation (LTP) and synaptic plasticity [21], with important roles in temporal regulation of neuronal activity
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