Induction of c-fos and interleukin-2 genes expression in the central nervous system following stressor stimuli

An injection of 5% mustard in vegetable oil, an injection of vegetable oil and needle prick into a rat leg gastrocnemius muscle were selected as stressor stimuli. Expression of c-fos mRNA and interleukin-2 (IL-2) mRNA was measured using digoxigenin labeled cDNA probe. C-fos-like proteins were determined by an immunochemical method with anti-c-fos polyclonal antibodies. Thirty min after the injection of 5% mustard in vegetable oil, c-fos mRNA synthesis was shown in the sacral segments of the spinal cord. Many c-fos mRNA labeled cells were noted also in the hypothalamus (paraventricular nucleus, dorsomedial nucleus, and the lateral hypothalamic area), thalamus, hippocampus, nucleus caudatum, sensori-motor zone of the brain cortex and the amygdaloid complex. Expression of c-fos-like proteins was shown after the injection of vegetable oil and 5% mustard in vegetable oil (within 2 h) in the spinal cord structures, the maximum quantity of the labeled cells was found in the I and II sacral segments (in the superficial lamina of the gray matter of the dorsal horns in the ipsilateral side), the minimum in the IV and V lumbar segments (in the intermediate zone of the gray matter at the level of the central canal). When c-fos-like proteins expression were analyzed in the CNS, c-fos-labeled cells were detected in the same structures where c-fos mRNA was also shown. The IL-2 mRNA synthesis was shown within 2 h after the stimulus in the same brain structures as c-fos mRNA. It is always difficult to destinguish the effect of stress as sensory stimuli or as general stimuli. The c-fos immunoreactivity appeared mostly in the contralateral side of the hypothalamus, therefore maybe in our investigation the mechanism of sensory stimuli mostly results in the changes that have been obtained. The information of applied stimuli arrived in the spinal cord, and is transmitted to the brain where it activates certain brain structures inducing c-fos and IL-2 genes expression. The most important conclusion is that the used stress stimuli induced not only c-fos gene but also IL-2 gene expression in the brain. The synthesis of both mRNA takes place in the same brain structures.