Ischemic preconditioning (IPC) via
protein kinase C epsilon (PKCɛ) activation induces neuroprotection against lethal
ischemia.
Brain-derived neurotrophic factor (
BDNF) is a pro-survival signaling molecule that modulates synaptic plasticity and neurogenesis. Interestingly,
BDNF mRNA expression increases after IPC. In this study, we investigated whether IPC or pharmacological preconditioning (PKCɛ activation) promoted
BDNF-induced neuroprotection, if neuroprotection by IPC or PKCɛ activation altered neuronal excitability, and whether these changes were
BDNF-mediated. We used both in vitro (hippocampal organotypic cultures and cortical neuronal-glial cocultures) and in vivo (acute hippocampal slices 48 hours after preconditioning) models of IPC or PKCɛ activation.
BDNF protein expression increased 24 to 48 hours after preconditioning, where inhibition of the
BDNF Trk receptors abolished neuroprotection against
oxygen and
glucose deprivation (OGD) in vitro. In addition, there was a significant decrease in neuronal firing frequency and increase in threshold potential 48 hours after preconditioning in vivo, where this threshold modulation was dependent on
BDNF activation of Trk receptors in excitatory cortical neurons. In addition, 48 hours after PKCɛ activation in vivo, the onset of anoxic depolarization during OGD was significantly delayed in hippocampal slices. Overall, these results suggest that after IPC or PKCɛ activation, there are
BDNF-dependent electrophysiologic modifications that lead to neuroprotection.