The brain was sectioned down to the level of the piriform cortex, and 12 alternate 30-micron sections were taken through it.
For cell counts, three anatomical regions of layer II of the piriform cortex on each side of the brain were selected, as this location has previously been described as being a particularly vulnerable area of the developing brain for anesthetic-induced neurotoxic injury .
This 60,000 [micro][m.sup.2] grid was placed over each of the six preassigned areas (i.e., I-VI) of layer II of the piriform cortex, and the total number of granule cells seen under regular light in each of these field areas was counted, that is, six separate grid areas were counted along the piriform cortex, each of 60,000 [micro][m.sup.2] area.
Since six segments of piriform were counted in each brain section, the total volume of the piriform cortex analyzed per brain section was 10,800,000 [micro][m.sup.3].
Hence, using measured cell counts, mean [+ or -] SEM values were calculated for each brain with the results expressed as the (a) total cell count per piriform cortex and (b) total eosinophilic cells per piriform cortex.
Total cell counts were calculated for layer II of the piriform cortex of each of the drug-treated animals, and a mean [+ or -] SEM value was calculated for each study group.
Mean values were generated for each of the study groups for the number of dying cells per piriform cortex, and drug groups were compared to controls.
The piriform cortex receives input from the olfactory bulb and sends efferents to the hippocampus via the entorhinal cortex.
Strikingly, the same protocols did not induce long-term information storage in the form of synaptic plasticity in the piriform cortex.
The scientists wondered whether the piriform cortex needs to be instructed to create a long-term memory.
To demonstrate central action of EOX, c-Fos labeled by immunofluorescence was performed showing activation of olfactory bulb, piriform cortex, and periaqueductal gray (PAG).
Treatment Dose Olfactory bulb (mg/kg) Vehicle -- 3.5 [+ or -] 0.6 EOX 12.5 11.7 [+ or -] 2.6 EOX 25 22.0 [+ or -] 5.4 (a) EOX 50 25.7 [+ or -] 6.4 (b) Treatment FOS positive cells Periaqueductal gray Piriform cortex Vehicle 3.0 [+ or -] 1.4 4.2 [+ or -] 1.3 EOX 8.0 [+ or -] 1.7 23.7 [+ or -] 5.2 (a) EOX 29.5 [+ or -] 3.6 (b) 28.7 [+ or -] 1.1 (b) EOX 34.0 [+ or -] 9.4 (b) 19.2 [+ or -] 3.6 (a) n = 4, per group; values represent mean [+ or -] S.E.M.