Elicitation interval dependent spatiotemporal evolution of cortical spreading depression waves revealed by optical intrinsic signal imaging

Abstract

This study aimed to investigate the variation of propagation patterns of successive cortical spreading depression (CSD) waves induced by K⁺ or pinprick in rat cortex. In the K⁺ induction group, 18 Sprague-Dawley rats under α-chloralose/urethane anesthesia were used to elicit CSD by 1 M KCl solution in the frontal cortex. Optical intrinsic signal imaging (OISI) at an isosbestic point of hemoglobin (550 nm) was applied to examine regional cerebral blood volume (CBV) changes in the parieto-occipital cortex. In 6 of the 18 rats, OISI was performed in conjunction with DC potential recording of the cortex. The results of this group were reported previously. In the pinprick group, 6 rats were used to induce CSD by pinprick with 8 min interval, and the other 6 rats were pricked with 4 min. CBV changes during CSD appeared as repetitive propagation of wave-like hyperemia at a speed of 3.7±0.4 mm/min, which was characterized by a significant negative peak (-14.3±3.2%) in the reflectance signal. Except for the first CSD wave, the following waves don't spread fully in the observed cortex all the time and they might abort in the medial area. Independent on the stimulation of pinprick or K+, a short interval of the current CSD to the last CSD no more than 4 min would induce the current CSD be partially propagated. For the first time, the data reveals the time-varying propagation patterns of CSD waves might be affected by the interval between CSD waves. The results suggest that the propagation patterns of a series of CSD waves are time-varying in different regions of rat cortex, and the variation is related to the interval between CSD waves.