The reactions of bilateral adrenalectomy (14 days) on the rat glial fibrillary acidic-immunoreactive elements of the third ventricular ependyma and adjacent neuropil were analyzed using histological, immunohistochemical and morphometric methods. Bilateral adrenalectomy led to a drastic increase in the number of immunoreactive elements located in the neuropil adjacent to the third ventricle and the optic chiasm when compared to normal and sham-operated animals (p < 0.05). By contrast, the adrenalectomized animals receiving corticosterone showed the same characteristics and morphometric values as those found in normal and sham-operated animals. The results show that the participation of the adrenal gland in astroglial responses should be taken into account.