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Updated: Mar 29, 2026
Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices
Published on: April 5, 2016
G Protein-Gated K+ Channel Ablation in Forebrain Pyramidal Neurons Selectively Impairs Fear Learning
Nicole C Victoria1, Ezequiel Marron Fernandez de Velasco1, Olga Ostrovskaya2
1Departments of Pharmacologyand Neuroscience, University of Minnesota, Minneapolis, Minnesota.
Background:
Cognitive dysfunction occurs in many debilitating conditions including Alzheimer's disease, Down syndrome, schizophrenia, and mood disorders. The dorsal hippocampus is a critical locus of cognitive processes linked to spatial and contextual learning. G protein-gated inwardly rectifying potassium ion (GIRK/Kir3) channels, which mediate the postsynaptic inhibitory effect of many neurotransmitters, have been implicated in hippocampal-dependent cognition. Available evidence, however, derives primarily from constitutive gain-of-function models that lack cellular specificity.
Methods:
We used constitutive and neuron-specific gene ablation models targeting an integral subunit of neuronal GIRK channels (GIRK2) to probe the impact of GIRK channels on associative learning and memory.
Results:
Constitutive Girk2-/- mice exhibited a striking deficit in hippocampal-dependent (contextual) and hippocampal-independent (cue) fear conditioning. Mice lacking GIRK2 in gamma-aminobutyric acid neurons (GAD-Cre:Girk2flox/flox mice) exhibited a clear deficit in GIRK-dependent signaling in dorsal hippocampal gamma-aminobutyric acid neurons but no evident behavioral phenotype. Mice lacking GIRK2 in forebrain pyramidal neurons (CaMKII-Cre(+):Girk2flox/flox mice) exhibited diminished GIRK-dependent signaling in dorsal, but not ventral, hippocampal pyramidal neurons. CaMKII-Cre(+):Girk2flox/flox mice also displayed a selective impairment in contextual fear conditioning, as both cue fear and spatial learning were intact in these mice. Finally, loss of GIRK2 in forebrain pyramidal neurons correlated with enhanced long-term depression and blunted depotentiation of long-term potentiation at the Schaffer collateral/cornu ammonis 1 synapse in the dorsal hippocampus.
Conclusions:
Our data suggest that GIRK channels in dorsal hippocampal pyramidal neurons are necessary for normal learning involving aversive stimuli and support the contention that dysregulation of GIRK-dependent signaling may underlie cognitive dysfunction in some disorders.
