Nitric oxide in the penumbra of a focal cortical necrosis in rats.

After a focal cortical freezing lesion in rats, nitric oxide (NO) end products were studied with microdialysis in the extracellular space of the penumbra throughout the whole period of secondary expansion of the cortical necrosis (i.e. 24 h). Under baseline conditions, the dialysate concentration of nitrate (nitrite) was 1.8 +/- 0.78 microM (5.00 +/- 1.50 microM) in the sham-operated group and 2.28 +/- 0.62 microM (3.25 +/- 1.32 microM) in the trauma group. In animals of both groups, these parameters neither showed significant alterations within the observation period compared with baseline values nor between the groups at each individual study time point. After focal cortical trauma, NO does not mediate secondary necrosis expansion via the extracellular space.