Glial repair in an insect central nervous system: effects of surgical lesioning.

Surgical lesioning of central nervous connectives in the cockroach (Periplaneta americana (L.], although causing only local glial damage, resulted in complex and prolonged cellular changes. An early response to mechanical disruption was the appearance of granule-containing cells within the damaged perineurium, among adjacent, undamaged, perineurial cells, and between glial processes deep within the connectives. These cells, which were strikingly similar to hemocytes, were clearly involved in phagocytic activity and persisted in the damaged regions for more than a month after lesioning. There was only a slow restoration of organized perineurial glia and re-establishment of the blood-brain barrier, as indicated by the exclusion of an extracellular tracer, ionic lanthanum. These observations contrast with the speedy, ordered repair of the neuroglia observed following selective glial disruption and suggest that undamaged axons and/or the extracellular matrix exert a profound influence on the mechanisms of glial repair.