Effects of chronic postnatal opioid receptor blockade by naltrexone upon proliferation capacity in the prenatally X-irradiated brain of the rat.
We recently reported that in rats prenatally X-irradiated on gestation day 14 with 1 Gy, postnatal chronic application of the opioid antagonist naltrexone (NX) led to a remarkable growth spurt of the microencephalic brain. In the present study we present histological and autoradiographic results found in the subependymal layer (SEL) of the forebrain lateral ventricles. NX led to an intermittent augmentation of the mitotic index of the X-irradiated brains within a postnatal observation period of 24 weeks. The most conspicuous finding was transient hyperplasia of the SEL at 4-6 weeks of age which occurred in close proximity to an intact ependymal lining. Districts of the lateral ventricles which were denuded from ependyme and where the rest of the ependymal layer (EL) was dislocated peripherally showed upon NX treatment a long-lasting SEL hyperplasia with a tendency towards dysplasia. These results revealed that repair proliferation of embryotoxic X-irradiation is normally under strong control by the opioid system. If that system, which exerts a suppressing effect upon glial growth, is blocked by NX, prominent hyperplastic reactions occur which may be useful for repairing the lesion pattern.
Schmahl
W
W
Department of Pathology, Gesellschaft für Strahlen-und Umweltforschung mbh Müchen, Neuherberg, West Germany.
Miaskowski
U
U
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000473:pathology / Q000528:radiation effects; D002455:Cell Division / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D008297:Male; D009271:Naltrexone / Q000494:pharmacology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects* / Q000528:radiation effects
D011957:Receptors, Opioid; D009271:Naltrexone