Interferon-gamma-responsive neuronal sites in the normal rat brain: Receptor protein distribution and cell activation revealed by Fos induction

Constitutive expression of the interferon-gamma receptor protein (IFN-gamma R), and the distribution of cells in which Fos, a marker of cell activatio n, is induced by intracerebroventricular administration of IFN-gamma, were studied in the rat brain by immunohistochemistry, IFN-gamma R immunopositiv ity was found in neuronal elements, which exhibited a selective distributio n being concentrated in the piriform and entorhinal cortex, midline thalamu s and medial hypothalamic structures, brainstem nociceptive relays (includi ng the periaqueductal gray, the parabrachial nuclei and the caudal part of the spinal trigeminal nuclei), and circumventricular organs such as the med ian eminence and area postrema. IFN-gamma-induced Fos expression mostly cor responded to neuronal sites of receptor distribution. Because of its topogr aphical distribution, it is suggested that activation of the IFN-gamma R in neurons may play a role to limit spread of infections in the brain and, in concert with other proinflammatory cytokines, to modulate adaptive respons es to an antigen challenge mediated by the central nervous system. (C) 2000 Elsevier Science Inc.