INFRAORBITAL NERVE TRANSECTION AND WHISKER FOLLICLE REMOVAL IN ADULT RATS AFFECT MICROGLIA AND ASTROCYTES IN THE TRIGEMINAL BRAIN-STEM - A STUDY WITH LIPOCORTIN1-IMMUNOHISTOCHEMISTRY AND S100-BETA-IMMUNOHISTOCHEMISTRY

Transections of the infraorbital nerve in adult rats resulted in progr essive alterations of microglia identified by Lipocortin1 immunoreacti vity at the sites where the primary afferents terminate, i.e. in the t rigeminal brainstem sensory nuclei. Microglia proliferated three- to f our-fold. Their cell bodies enlarged and their processes thickened. Mi croglial responses were similar to the removal of whisker follicles. H owever. they were restricted to discrete nuclear subregions that match ed with the known whisker somatotopy. Astrocytes identified by S100 be ta immunoreactivity showed minor increases in size and in population d ensity. No microglial or astrocytic reactions were found in the second and third synaptic relays of the somatosensory pathway. Because both types of lesion reportedly lead to the reorganization of primary affer ents, our results establish the two experimental designs as valuable t ools to elucidate the role of microglia and Lipocortin1 in adult brain plasticity. (C) 1997 IBRO. Published by Elsevier Science Ltd.