Astroglial cell alteration caused by neurotoxins: immunohistochemical observations with antibodies to glial fibrillary acidic protein, laminin, and tyrosine hydroxylase.

Kainic acid or 6-hydroxydopamine (6-OHDA) was injected into rat striatum, and their effects on astrocytes, laminin, and catecholamine fibers were examined temporally by immunohistochemical methods in an attempt to understand the roles of reactive astrocytes and laminin on the restoration of central nervous tissue. Kainic acid injection caused a severe neuronal degeneration in the striatum but catecholamine fibers were spared with only transient loss of tyrosine hydroxylase immunoreactivity. Reactive astrocytes appeared around the lesioned area soon after the kainic acid injection, then migrated into that area, and finally covered the lesioned striatum. Laminin immunoreactivity was found only in the lesioned area before the migration of reactive astrocytes and disappeared when the area was covered by astrocytes. 6-OHDA injection, on the other hand, resulted in a severe degeneration of catecholamine fibers, but striatal neurons were mostly spared. From 7 to 28 days after injection, regenerating fibers were found to enter the affected region. In this period reactive astrocytes were seen in the affected region but were only slightly more numerous than those found in control (saline injected) striatum. Laminin-immunoreactive blood vessels seemed to show a distribution similar to that in control striatum. These observations indicate that reactive astrocytes may play an important role in areas of neuronal cell loss and that laminin may aid their migration into such areas. Laminin and reactive astrocytes may not, however, be essential for the regeneration of dopamine fibers.