A Novel Approach to Study Gamma-Band Coherence in Ex Vivo Hippocampal Slices from a Mouse Model of Bipolar Disorder

Oscillations play crucial roles in many cognitive processes such as memory formation and attention. GABAergic interneurons can synchronize neuronal activity leading to gamma oscillations (30-60 Hz). Abnormalities in oscillatory activity in the hippocampus have been implicated in the pathology of some mental health disorders including schizophrenia and bipolar disorder, however the neurobiological mechanism underlying these abnormal oscillations are not yet fully understood. We set out to develop a reliable approach to study gamma oscillations in ex vivo hippocampal preparations using perforated microelectrode arrays. Perforated microelectrode arrays allow for the simultaneous measurement of electrical activity at multiple sites while allowing solutions to pass through the brain section. We obtained extracellular electrophysiological recordings from acute sections of mouse hippocampus situated on a 60-channel, perforated microelectrode arrays (pMEAs). Bath application of kainate rapidly induced and maintained oscillatory activity in the CA1 and CA3 regions of the hippocampus. Kainate-induced oscillations were quickly abolished by the GABAA receptor antagonist, bicuculline. Furthermore, we employed this approach on a mouse model of bipolar disorder. Sections prepared from mutant mice exhibited an increase in the coherence of gamma power within CA1 despite a reduction in gamma-band power.