Fos expression in neurons immunoreactive for neuronal nitric oxide synthase in the rat paraventricular nucleus after intraperitoneal injection of interleukin-1 beta

Double immunostaining for Fos and neuronal nitric oxide synthase (nNOS) was used to examine whether nNOS-immunoreactive neurons in the paraventricular hypothalamic nucleus (PVN) are activated to express Fos immunoreactivity b y intraperitoneal injection of interleukin-1 beta (IL-1 beta) in the rat. Q uantitative analysis revealed that some nNOS-positive PVN neurons are activ ated by IL-1 beta (4 mug/kg, i.p.) administration, but the majority of the IL-1 beta -activated PVN neurons do not express nNOS and are distributed ma inly in the parvocellular part of the PVN. (C) 2000 Elsevier Science Irelan d Ltd and the Japan Neuroscience Society. All rights reserved.