Abstracts

Rationale: Neuronal activity is coupled to cellular metabolism. The glycolytic inhibitor, 2-deoxy-D-glucose (2-DG), has been previously shown to have both acute anticonvulsant and chronic antiepileptic effects (Ann Neurol 65:435, 2009), but the underlying mechanisms remain to be elucidated. This study aimed to further investigate the action and mechanisms of 2-DG on neuronal activity at the membrane level (intrinsic excitability), neuronal level (spontaneous firing of individual neurons), and network level (population bursting). Methods: Hippocampal slices were prepared from 11-22 day-old Sprague-Dawley rats. Single or dual whole-cell recordings, extracellular field-potential recording, or simultaneous field potential and whole cell/cell-attached recordings were conducted in hippocampal CA3 and CA1 to assess the 2-DG action. Results: The effect of 2-DG on membrane excitability was examined in CA1 pyramidal cells. Intracellular application of 2-DG (10 mM) did not significantly alter membrane input resistance, action potential threshold, firing pattern or input-output relationship, as compared to that in simultaneously recorded neighboring neurons without intracellular 2-DG (p>0.05, n=7 pairs). The action of 2-DG on individual neuron firing was tested on spontaneous firing in CA3 pyramidal cells (n=6) and K+-or 4-aminopyridine (4-AP)-induced firing in CA1 neurons (n=4). Bath application of 10 mM 2-DG blocked both types of firing. Network bursts were induced in CA3 area by perfusing slices with Mg2+-free medium containing 50 M 4-AP. Bath application of 10 mM 2-DG completely and irreversibly abolished epileptiform bursts in nearly all slices after ~10 minutes (7 of 8 slices). Moreover, addition of downstream metabolites pyruvate (n=4) or phosphoenolpyruvate (PEP) plus ADP (n=6) did not prevent the 2-DG effects. Furthermore, in contrast to bath application, direct intracellular delivery of 2-DG into individual CA3 or CA1 neurons failed to block neuronal firing, indicating that these neurons may obtain energy from an extracellular source to maintain their activity. Finally, in this model, bath application of 10 mM 2-DG caused irreversible membrane depolarization in active neurons, which might indicate neuronal damage. Conclusions: These data suggest that neuronal activity is tightly coupled to metabolic states; glycolytic inhibition with 2-DG can effectively suppress epileptiform activity but may also lead to neuronal damage. The data also suggest that sustained neuronal firing requires an extracellular source of energy, presumably from glial cells. Funding: Supported by Johns Hopkins University Haller Distinguished Professorship startup funding to CES.