Effect of chronic lead exposure in various doses on the pyramidal cell neurons of the developing cerebral cortex in young rats [light and electron microscopic study]

ABSTRACT

Lead represents a toxin which affects the developing nervous system with neuro-behavioural deficits. The present study was planned with the aim of studying the morphological changes that might occur in the cerebrum of the young rats in response to two different doses of the lead for 3 months, and discover whether these changes are reversible or irreversible. Fifty young albino rats, aged 4-5 weeks, were used in the present work. They are classified into 3 groups a control group [10 rats], group "A" [20 rats] received a low dose of lead acetate for 3 months, and group "B" [20 rats] received a high dose of lead acetate for 3 months. Ten rats of both groups "A" and "B" were sacrificed one month after the last given dose of lead [ie. recovery animals]. The cerebral cortex of the young rats of the group "A" showed that pyramidal cell neurons are little in number. Some of them are atrophic and other showed either degenerating mitochondria and dilated Golgi apparatus or ill-defined cytoplasmic organelles. Also, there is obvious perivascular oedema. In addition, most myelinated axons showed vacuolation of their myelin sheaths. The cerebral cortex of the young rats of the group "B" showed that most of the pyramidal cell neurons are distorted, with irregular nuclear membrane, proliferative endoplasmic reticulum, dilated Golgi apparatus and degenerating mitochondria. Also, wide-spread gliosis and extensive pericellular oedema were evident. Most myelinated axons showed vacuolation of myelin sheaths, and vacuolated or ill-defined axoplasm. The cerebral cortex of the recovery animals of the group "A" showed nearly complete recovery, while that of the group "B" showed incomplete recovery in the form of perivascular oedema and abnormal myelinated and non-myelinated axons