Optical imaging of neural activity in a rat hippocampal slice in an ischemia-like condition

Abstract

We visualized neural activity evoked by stimulating Schaffer collaterals in the CA1 regions in a rat hippocampal slice preparation, and anlayzed the effect of exposure to an ischemia-like condition at room temperature. We recorded also field potentials from the nearby pyramidal cell layer. Optical signals revealed propagation of action potentials in the molecular/radiatum layers in both directions from the stimulated site, followed by activation of pyramidal/oriens layers, and at the later phase spread to more lateral regions. In an ischemia-like condition in which oxygen and glucose were removed from the perfusing fluid, population spikes and/or slow potentials gradually reduced and disappeared, while optical signals remained only at the stimulation locus. When the perfusate solution was switched to the normal fluid within 10 min population spikes and the optical signals restored to the control level after 15-30 min. These observations demonstrated that generation of neural activities in Schaffer collaterals are the most resistive, but that synaptic transmissions are very sensitive to ischemia-like condition.