Propagation of epileptiform events across the corpus callosum in a cingulate cortical slice preparation

• Published in: PloS one 2012-02, Vol.7 (2), p.e31415-e31415
• Main Authors: Walker, Jeffrey, Storch, Gregory, Quach-Wong, Bonnie, Sonnenfeld, Julian, Aaron, Gloster
• Format: Article
• Language: English
• Subjects: Animals; Axons; Axons - drug effects; Axons - physiology; Behavior; Bicuculline; Bicuculline - pharmacology; Biology; Brain; Brain slice preparation; Calcium - metabolism; Cerebral hemispheres; Chloride; Corpus callosum; Corpus Callosum - drug effects; Corpus Callosum - physiopathology; Cortex; Diagnostic Imaging; Dizocilpine; Dizocilpine Maleate - pharmacology; Epilepsy; Epilepsy - physiopathology; Extracellular Space - drug effects; Extracellular Space - physiology; Female; GABA; Glutamic acid receptors (ionotropic); Gyrus Cinguli - drug effects; Gyrus Cinguli - physiopathology; Hemispheres; In Vitro Techniques; Inhibitory Postsynaptic Potentials - drug effects; Magnesium; Magnesium - pharmacology; Male; Medicine; Mice; Microinjections; Models, Neurological; N-Methyl-D-aspartic acid receptors; Neural networks; Neurons; Neurosciences; Perfusion; Potassium; Propagation; Sodium; Solutions; Sucrose; Walker, Jeffrey; γ-Aminobutyric acid
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0031415

We report on a novel mouse in vitro brain slice preparation that contains intact callosal axons connecting anterior cingulate cortices (ACC). Callosal connections are demonstrated by the ability to regularly record epileptiform events between hemispheres (bilateral events). That the correlation of these events depends on the callosum is demonstrated by the bisection of the callosum in vitro. Epileptiform events are evoked with four different methods: (1) bath application of bicuculline (a GABA-A antagonist); (2) bicuculline+MK801 (an NMDA receptor antagonist), (3) a zero magnesium extracellular solution (0Mg); (4) focal application of bicuculline to a single cortical hemisphere. Significant increases in the number of epileptiform events, as well as increases in the ratio of bilateral events to unilateral events, are observed during bath applications of bicuculline, but not during applications of bicuculline+MK-801. Long ictal-like events (defined as events >20 seconds) are only observed in 0Mg. Whole cell patch clamp recordings of single neurons reveal strong feedforward inhibition during focal epileptiform events in the contralateral hemisphere. Within the ACC, we find differences between the rostral areas of ACC vs. caudal ACC in terms of connectivity between hemispheres, with the caudal regions demonstrating shorter interhemispheric latencies. The morphologies of many patch clamped neurons show callosally-spanning axons, again demonstrating intact callosal circuits in this in vitro preparation.