Figure 1.

Experimental design. (A) Rat brain viewed from above. Cortical spreading depression (CSD) was elicited in the right frontal cortex with a brief needle stab, and propagated into the right somatosensory cortex monitored by a glass microelectrode recording electrocorticographic (ECoG) activity. Using the same microelectrode, we recorded local field potentials (LFPs) evoked by a bipolar stimulation electrode placed in the contralateral somatosensory cortex. Baseline and evoked changes in cerebral blood flow (CBF) were recorded by laser Doppler flowmetry (LDF), while tissue oxygenation (tpO₂) was recorded using a Clark-type polarographic glass microelectrode. (B) Cerebral metabolic rate of oxygen (CMRO₂) was calculated offline from simultaneous measurements of CBF and tpO₂. Evoked CBF, tpO₂, and CMRO₂ responses were defined as area under curve (AUC) from stimulation onset to peak value. Evoked LFP responses were defined by their peak amplitude. (C) The experimental protocol started with recordings of evoked responses (trains lasting 1 second of 1, 6, and 20 Hz stimulation, repeated three times). Topical application of drug (cyclosporine A (CsA), FK506, NIM811, or FK506+NIM811) followed. Incubation lasted for minimum 30 minutes before repeating evoked responses as stated above. CSD was elicited and between 20 to 60 minutes after CSD-evoked responses were repeated again. Changes in ongoing CBF and CMRO₂ were evaluated both during the hyperemia phase (‘early changes') and during the oligemia phase (‘prolonged changes'). The effects of vasoconstrictor U46619 were tested in separate experiments (protocol not shown in this figure).