Module 10: Figure gamma oscillatory mechanism
Hippocampal gamma oscillatory mechanism.
The inhibitory basket cell (red) and the excitatory CA3 pyramidal neuron (green) interact with each other to form a network oscillator that is tuned to generate gamma oscillations. The collateral axons of the CA3 neuron release glutamate that depolarizes the basket cell whose axon terminals innervate the CA3 neurons to releases GABA, which then acts on GABAA receptors (GABAARs) to induce the inhibitory postsynaptic potentials (IPSPs) which hyperpolarize the membrane to temporarily curtail the firing of the CA3 neurons. Operation of this self-contained network oscillator appears to be driven by a tonic excitatory drive that is activated by inputs from other brain regions such as the cholinergic innervation received from the septal cholinergic input that releases acetylcholine (ACh), which acts through muscarinic 1 receptors (M1Rs). These metabotropic receptors appear to act by stimulating channels (dashed box) to provide the pacemaker depolarizations that drive oscillatory activity. See the text for information on the different signalling mechanisms that control this network oscillator.