Experimetal Microneurosurgery of the Central and Peripheral Nervous System in the Study of the Neuronal and Glial Trophism and Plasticity

Abstract

Trauma and neurodegenerative diseases commit the nervous system. After an axotomy or nerve injury in the peripheral nervous system the regeneration of the nerve fibers and reinervation of the target are seen. In central nervous system these events are restrictive, however their occurrence are related to the state of glial reaction and the synthesis of neurotrophic factors. Basic fibroblast growth factor (bFGF) has been considered an important trophic factor for neurons and astrocytes of many central nervous system regions. In this study rats were submitted to one of following neurosurgery procedures: callosotomy, pyramidectomy or complete transection of hypoglossal nerve (XII). Sham operations were made in control animals. Seven days later animals were sacrificed and their brains processed for immunohistochemistry. Coronal sections were taken from the central nervous system and incubated with antisera against the glial fibrillary acidic protein (GFAP) or neurofilament (NF), markers for astrocyte and neuronal cell body and fibers, respectively, as well as with the antiserum against the bFGF. The degree of the labelling was quantified with computer assisted stereological methods. The analysis of the NF immunoreactivity revealed a disappearance of fibers in the white matter distal to the pyramidectomy and callosotomy, however no disappearance of NF immunoreactive neurons was found in the XII nucleus following axotomy. These changes was accompanied by a massive astrocytic reaction. The reactive astrocytes synthesized increased amounts of bFGF. These findings suggest that glial reaction synthesizing neurotrophic factors may influence the wound and repair after mechanical lesions of central nervous and subsequent neuronal trophism and plasticity which may be relevant to the regenerative process of the nervous tissu

Differential astroglial responses in the spinal cord of rats submitted to a sciatic nerve double crush treated with local injection of cultured Schwann cell suspension or lesioned spinal cord extract: implications on cell therapy for nerve repair

“…Astrocytes are the counterpart of SC in the central nervous system. Likewise, astrocytes in the brain and spinal cord react after injury by changing their shape and by producing neurotrophic factors and immunoregulatory molecules 27 . Initial action is to promote wound and repair, by eliminating injured neurons and axons, and also restoring brain barriers 29 .…”

“…As there is no local wound related to tissue disruption, astroglial activation in the central nervous system after nerve lesion is mainly involved in paracrine mechanisms favoring neuronal survival and fi ber outgrowth. It seems likely that the astroglial, centrally, and SC, peripherally, may cooperate in the process of nerve repair, however only recently this issue started to be investigated 8,27 . Actually, there are many publications concerning the responses of peripheral neurons following a nerve lesion, however, a detailed analysis of the retrograde signals leading subsequent activation of glial cells close to motor neuron perikarya and to terminals of sensory neurons is still lacking.…”