A preparation and fixation technique suitable for quantitative immunohistochemistry and autoradiography of human brain tissue

The enzymatic changes in the facial nucleus of the rat occurring after single nerve transection were compared with those after double lesion. In a first operation the left facial nerve was transected and 2 weeks later, both the left and the right facial nerves were axotomized. The double or “conditioning” lesion produced a complex pattern of changes that differed from those after a single lesion. Three enzymes were investigated both biochemically and histochemically. Acetylcholinesterase is representative of the group of transmitter-related enzymes which in general showed a decrease after a single lesion. The hexose monophosphate shunt enzymes, represented here by glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, are known to increase in the perikaryon. 5′-Nucleotidase is a marker enzyme for the perineuronal satellite glia which also increase in number during chromatolysis. The following results were obtained: (i) In comparison with the single-lesion side the conditioning-lesion side exhibited less activity of the pentose phosphate shunt enzymes on days 7 and 12 after the second operation. On the conditioning-lesion side the amount of enzyme per perikaryon was higher on days 1 and 3, approximately the same on day 7, and less on day 12 compared with the single-lesion side. (ii) The conditioning-lesion side displayed a more pronounced decrease of acetylcholinesterase. (iii) 5′-Nucleotidase increased again after a second axotomy and reached the same level of activity as after a single lesion. These data suggest that a conditioning lesion does not simply amplify the ongoing axonal reaction of the cells in a linear fashion, but that it leads to a complex response. The data are in favor of a shorter initial delay prior to the axonal outgrowth which occurs after a conditioning lesion. However, our data could not explain an enhancement of axonal outgrowth velocity after the second operation.