Abstracts

Rationale: Intrinsic optical signal (IOS) imaging is useful tool to investigate neural activity. IOS imaging can observe brain metabolic change, such as hemodynamic change, noninvasively. In this study, we measured the alteration of cerebral blood flow (CBF) during afterdischarge (AD) induced by acute kindling of the rat hippocampus to reveal the progression of epileptic activity. Methods: We performed all experiments under appropriate conditions in accordance with the Guide for Animal Experimentation at Soka University. Five adult male Sprague-Dawley rats (250-500 g, Japan SLC Inc., Hamamatsu, Japan) were used. Under deeply anesthesia, we delivered stimulations (1 msec biphasic pulse, 50 Hz, 1 sec) with suprathreshold intensity for AD at 20-min intervals to the right hippocampus. Digitalizing of each AD was performed with sampling frequency of 1 kHz by Power 1401 (CED, Cambridge, England). The kindling stimulations were performed at least 15 times. Images were obtained from the bilateral hemisphere using a CCD camera (Rolera EM-C<+>2<+>; Q imaging, Surrey, Canada). The cortex was illuminated with filtered light from a tungsten-halogen light source (KTS-150-RSVS; Kenko, Hidaka, Japan). The 586nm, which is an isosbestic wavelength for oxyhemoglobin and deoxyhemoglobin, transmission filter was used. Results: In acute situation, rats could produce progressive increment of AD duration. In many case, CBF increased a few seconds later of kindling stimulation. Its CBF alteration maintained in proportion as duration of AD. Additionally, alteration of CBF on afterdicharge was observed bilaterally. Conclusions: It is suggested that metaboric change on afterdischarge might occur bilaterally and accompany change of local filed potentials.