Enzyme changes in the rat facial nucleus following a conditioning lesion.
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.
D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D005154:Facial Nerve / Q000201:enzymology* / Q000502:physiology; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D008297:Male; D009416:Nerve Regeneration; D009708:Nucleotidases / Q000378:metabolism; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D000110:Acetylcholinesterase; D009708:Nucleotidases