Remote Astrocytic Response of Prefrontal Cortex Caused by the Lesions in the Nucleus Basalis of Meynert

The nucleus basalis of Meynert (nbM) was lesioned by injection of ibotenic acid and the prefrontal cortices were subjected to immunohistochemical and Western blot analysis for the expression of glial fibrillary acidic protein (GFAP). In some rats, vehicle was injected into the nbM and in others 6-hydroxydopamine (6-OHDA) was injected into the ventral tegmental area (VTA). Quantitative Western blot analysis revealed significantly greater immunoreactivity for GFAP in the prefrontal cortex of nbM-lesioned rats. Immunohistochemical examination revealed fibrous and hypertrophic GFAP-positive astrocytes even one day after surgery, and this reaction was stronger at three days after surgery. In contrast, GFAP-positive astrocytes were not observed in the brains of vehicle-injected or VTA-lesioned rats, even 21 days after surgery. The present results indicate that cortical astrocytes respond to cholinergic deafferentation. In addition, the expression of amyroid precursor protein (APP) in the reactive astrocytes were examined by immunohistochemical techniques with antibody against APP. The reaction of astrocytes was induced by the deposition of kainic acid (KA) on the dura or the infusion of ibotenic acid into the ipsilateral nbM. The expression of GFAP was observed in the cortical astrocytes induced by both treatment, but the expression of APP was observed only in the reactive astrocytes in the cortex injected with KA. This suggests that the reaction of astrocytes is heterogeneous dependent on the feature of the lesion