Effect of internal irradiation on the maturing Purkinje cells in the rat. A Golgi study

Continuous irradiation in utero is reported to produce mental retardation and gross abnormalities of the brain in the human. A few experimental studies conducted so far also report gross brain defects in animals exposed to continuous irradiation in utero. Despite the increasing use of nuclear energy for power and radioisotopes in medicine, there is hardly any literature available on the effect of continuous irradiation on the structural details of the developing brain. After intraperitoneal injections of different doses of 131I (8, 18 and 32 microCi) and 32P (10 microCi) in new-born rats on the 6th postnatal day, cerebella stained by Golgi techniques were cut sagittally and the sections were examined on the 10th, 15th and 21st postnatal days. In the animals injected with 18 and 32 microCi of 131I and 10 microCi of 32P a large number of Purkinje cells showed morphological alterations not seen in the control groups or in the groups injected with 8 microCi of 131I. The changes observed included persistence of the perisomatic processes beyond the 10th postnatal day, multiple primary dendrites, angulation of the primary dendrites, long segments of primary dendrites without branches and significantly reduced dendritic volume. The number of affected cells was less on the 21st postnatal day. The effective radiation dose estimated in these groups ranged from 15 to 26 rad. Since the rats irradiated with 6 rad had not shown such changes it is believed that there is a threshold dose of radiation beyond which only changes are perceptible at neuronal level.