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 determined regionally in rats undergoing CSD (n = 8) and was significantly increased in cortex (14 +/- 7%) and hippocampus (10 +/- 6%) on the stimulated side relative to the contralateral hemisphere when tom pared with the same measurements in a control group (n = 8). A similar measurement using the physiologically inert radiotracer [C-14]iodoantipyrine to control for potential effects of CSD on radioligand distribution showed a minimal increase (2.4 +/- 0.7%) of radiotracer uptake in cortex after CSD. This increase was significantly less than that observed in the [H-3]nimodipine uptake studies. We hypothesize that increased in vivo [H-3]nimodipine uptake in CSD identifies regions of depolarization and thus infers activation of the L-type voltage sensitive calcium channels.