c-Fos expression in the central nervous system elicited by phrenic nerve stimulation

Phrenic nerve afferents (PNa) have been shown to activate neurons in the sp inal cord, brain stem, and forebrain regions. The c-Fos technique has been widely used as a method to identify neuronal regions activated by afferent stimulation. This technique was used to identify central neural areas activ ated by PNa. The right phrenic nerve of urethane-anesthetized rats was stim ulated in the thorax. The spinal cord and brain were sectioned and stained for c-Fos expression. Labeled neurons were found in the dorsal horn laminae I and II of the C-3-C-5 spinal cord ipsilateral to the site of PNa stimula tion. c-Fos-labeled neurons were found bilaterally in the medial subnuclei of the nucleus of the solitary tract, rostral ventral respiratory group, an d ventrolateral medullary reticular formation. c-Fos-labeled neurons were f ound bilaterally in the paraventricular and supraoptic hypothalamic nuclei, in the paraventricular thalamic nucleus, and in the central nucleus of the amygdala. The presence of c-Fos suggests that these neurons are involved i n PNa information processing and a component of the central mechanisms regu lating respiratory function.