Bilateral gliosis in unilaterally lesioned septohippocampal system: Changes in GFAP immunoreactivity and content

Abstract

Unilateral damage to the lateral fimbria led to a bilateral gliosis in the septum and hippocampus. The gliosis was manifested by an increase in GFAP staining, accompanied by an increased number of glial fibrillary acidic protein (GFAP)(+) cells and GFAP content; the latter however was not visible in the contralateral septum. In general, the contralateral reaction appeared weaker than the ipsilateral one. The pattern of contralateral increase in GFAP-immunoreactivity (IR) matched almost exactly that observed on the ipsilateral side in the hippocampus (the most evident increase was seen in the oriens and pyramidal layers of cornu Ammonis 3 and in polymorphic area of gyrus dentatus). In the septum the bilateral increase in GFAP-IR was mainly visible in the dorsolateral quadrant of the structure; however in the ipsilateral side it spread over the whole half of the structure. The astrocytic responses in the septum and hippocampus were not equivalent: they differed mainly with regard to the increase of GFAP(+) cells (over 300% of control in the anterior part of the septum and only about 120% in the dorsal hippocampus). The differences between the percentage increases of other gliotic indices: GFAP-IR and GFAP content. Various possibilities that may account for the occurrence of contralateral gliosis are discussed, the most plausible being the contribution of interhemispheric and intraseptal links and the action of some diffusible agents. We suggest that bilateral gliosis may have an impact on compensatory postlesion processes, possibly by providing trophic support to impaired neurons.

Retinal Laser Burn-Induced Neuropathy Leads to Substance P-Dependent Loss of Ocular Immune Privilege

“…The fact that the increase in NK1-R in the contralateral eye followed the appearance of NK1-R in the burned eye suggests that the burn initiated the neuronal signal. This observation is consistent with other reports that show a unilateral injury to the CNS leads to a bilateral response (39, 40). …”

Contralateral response of macrophages and astrocytes to injury in the cerebral hemisphere of 6‐day‐old rat following prenatal gamma irradiation

“…It is rather well documented that the response to unilateral brain injury is reflected by reactive changes within contralateral regions (Jegliński et al, 1995;Peinado et al, 1998). However, determinants of the contralateral response still need to be recognised in detail.…”

“…Apart from extensive experimental documentation of the tissue response within areas adjacent to the lesion site, there is growing evidence of reactive changes occurring at relatively much longer distances (Hajos et al, 1990;Jegliński et al, 1995;Peinado et al, 1998). Degeneration of interhemispheric neural connections following a focal injury of the cerebral hemisphere can evoke glial responses of contralateral locations.…”

Glial responses to steroids as markers of brain aging

“…Thus, injury or disease may account for the high interindividual variability in GFAP levels from the same brain region in aged humans (Harpin et al, 1990). However, differences in the intensity, distribution, and, in some instances, duration of astrogliosis suggest a differentiated rather than a stereotypic response to different stimuli (Norton et al, 1992;Laping et al, 1994d;Jelinski et al, 1995). Furthermore, an increase in GFAP gene expression in the brain of aged humans was found to be independent of neuropathology .…”