1. Electrical and Pharmacological Stimuli Reveal a Greater Susceptibility for CA3 Network Excitability in Hippocampal Slices from Aged vs. Adult Fischer 344 Rats
Daniel J. Kanak 2 3 ;Ryan T. Jones 2 ;Ashish Tokhi 2 ;Amy L. Willingham 2 ;Hitten P. Zaveri 4 ;Gregory M. Rose ;Peter R. Patrylo ;
1 Department of Anatomy, Southern Illinois School of Medicine Carbondale, IL USA ; 2 Department of Physiology, Southern Illinois School of Medicine Carbondale, IL USA ; 3 Center for Integrated Research in Cognitive and Neural Sciences, Southern Illinois School of Medicine Carbondale, IL USA ; 4 Department of Neurology, Yale University New Haven, CT USA ;
Figure 4 Effects of 200 nM kainate on CA3 network excitability Exposure to 200 nM KA modulated field potential activity in different ways in slices from aged and adult rats. A Epileptiform bursts persisted throughout the wash-in of 200 nM KA in the slight majority of slices from aged rats. Traces are truncated epileptiform bursts recorded in 100 and 200 nM KA in a slice from an aged rat. B The time-frequency pseudo-color plot shows the time course of DC-50 Hz normalized power spectral density 0–1, 1-min time steps, color coded blue to red from the experiment used in the illustration in panel A. Peak power remained concentrated at low frequencies 5 Hz associated with the rhythmicity of epileptiform bursts. C Conversely, 200 nM KA abolished epileptiform activity in the majority of slices from adult rats. Field potential responses in this subset of slices were also variable: the suppression of epileptiform bursts could be followed by unsynchronized activity arrow marked ‘1’, synchronous theta oscillations arrow marked ‘2’, or synchronous gamma oscillations arrow marked ‘3’. For clarity, a single truncated burst recorded from an adult slice in 100 nM KA is shown as the initial condition for the three types of response . D Similar to B, the time course of DC-50 Hz normalized power spectral density during wash-in of 200 nM KA is shown for a slice from an adult rat in which peak power transitioned from low frequencies associated with epileptiform bursts to higher frequencies 25–30 Hz associated with gamma oscillations. Overall, slices from aged rats were significantly less likely than adults to exhibit a suppression of “pathological” network activity i.e., epileptiform bursts that was followed by a transition to the more “physiological” theta and gamma oscillations p = 0.044, Fisher’s exact test.
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