Motor abnormalities and changes in the noradrenaline content and the cytoarchitecture of developing cerebellum following X-irradiation at birth.
We have studied the developmental time-course of changes in the noradrenaline (NA) content of cerebellum (CE), cytoarchitecture of the cerebellar cortex, and motor abnormalities induced by the exposure of the cephalic end of rats to a single dose (5 Gy) of X-irradiation immediately after birth. At all ages examined, i.e., from postnatal (PN) d 5 to 90, CE from exposed animals show a marked atrophy, with an agranular cortex that has lost its layered structure. Purkinje cells are scattered at all depths in the cortex, and their primary dendrite is randomly oriented. The motor syndrome includes dystonia-like movements, a fine tremor, and an ataxic gait. Being progressive, the abnormal movements are evident from PN d 10, and fully developed by d 30. On the other hand, no differences in cerebellar NA content between X-irradiated rats and age-matched nonirradiated controls were detected from PN d 5 to 60. However, at PN d 90 a significant increase in NA content of CE from exposed animals is found when compared to either age-matched controls (+36%, p < 0.01), or data from irradiated rats obtained at PN d 5 to 60 (p < 0.01). These results indicate a temporal dissociation between the motor and cytoarchitectural abnormalities and the increase in cerebellar NA content produced by a single dose of X-rays at birth. The late increase in cerebellar NA content might represent a compensatory response of noradrenergic terminals to an altered information flow out of the cerebellar cortex induced by the ionizing noxa.
Guelman
L R
LR
Departamento de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Zieher
L M
LM
Ríos
H
H
Mayo
J
J
Dopico
A M
AM
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001522:Behavior, Animal / Q000528:radiation effects; D002525:Cerebellar Cortex / Q000473:pathology / Q000528:radiation effects; D002531:Cerebellum / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D005260:Female; D008297:Male; D009069:Movement Disorders / Q000209:etiology* / Q000503:physiopathology; D009638:Norepinephrine / Q000378:metabolism*; D009929:Organ Size / Q000528:radiation effects; D011689:Purkinje Cells / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D014965:X-Rays
D009638:Norepinephrine