Role of GirK Channels in Long-Term Potentiation of Synaptic Inhibition in an In Vivo Mouse Model of Early Amyloid- Pathology.

Imbalances of excitatory/inhibitory synaptic transmission occur early in the pathogenesis of Alzheimer's disease (AD), leading to hippocampal hyperexcitability and causing synaptic, network, and cognitive dysfunctions. G-protein-gated potassium (GirK) channels play a key role in the control of neuronal excitability, contributing to inhibitory signaling. Here, we evaluate the relationship between GirK channel activity and inhibitory hippocampal functionality in vivo. In a non-transgenic mouse model of AD, field postsynaptic potentials (fPSPs) from the CA3⁻CA1 synapse in the dorsal hippocampus were recorded in freely moving mice. Intracerebroventricular (ICV) injections of amyloid- (A) or GirK channel modulators impaired ionotropic (GABA-mediated fPSPs) and metabotropic (GirK-mediated fPSPs) inhibitory signaling and disrupted the potentiation of synaptic inhibition. However, the activation of GirK channels prevented A-induced changes in GABA components. Our data shows, for the first time, the presence of long-term potentiation (LTP) for both the GABA and GirK-mediated inhibitory postsynaptic responses in vivo. In addition, our results support the importance of an accurate level of GirK-dependent signaling for dorsal hippocampal performance in early amyloid pathology models by controlling the excess of excitation that disrupts synaptic plasticity processes.