IN-VIVO UPTAKE OF [H-3] NIMODIPINE INTO BRAIN DURING CORTICAL SPREADING DEPRESSION

We report autoradiographic measurements of the in vivo uptake of [H-3] nimodipine during the nonischemic depolarization of cortical spreading depression (CSD) in rat brain. [H-3]Nimodipine uptake in brain was de termined regionally in rats undergoing CSD (n = 8) and was significant ly increased in cortex (14 +/- 7%) and hippocampus (10 +/- 6%) on the stimulated side relative to the contralateral hemisphere when tom pare d with the same measurements in a control group (n = 8). A similar mea surement using tile physiologically inert radiotracer [C-14]iodoantipy rine to control for potential effects of CSD on radioligand distributi on showed a minimal increase (2.4 +/- 0.7%) of radiotracer uptake in c ortex after CSD. This increase was significantly less than that observ ed in the [H-3]nimodipine uptake studies. We hypothesize that increase d in vivo [H-3]nimodipine uptake in CSD identifies regions of depolari zation and thus infers activation of the L-type voltage sensitive calc ium channels.