Effects Of Restraint Water-immersion Stress (RWIS) On Fos Expression In The Spinal Cord And Brainstem In Rats

The rat under restraint water-immersion stress(RWIS) is widely used to study the stress-induced gastric ulcer and to find the medicine that can cure this disease. The results of many experiments indicated that the RWIS-induced gastric ulcer was mostly due to the hyperactivity of parasympathetic that control the stomach while other stresses induced the enhancement of hypothalamo-pituitary-adrenocortical axis (HPA axis) and sympathetic-adrenomedullar (SA). Parasympathetic nerve innervating the stomach is the vagal nerve which are largely from dorsal motor nucleus of the vagus (DMV) and partly from nucleus ambiguus (NA).As the center of parasympathetic preganglionic, NA, DMV and nucleus of solitary tract (NTS) all regulate gastric motility. However, there are no unanimous standpoints about the excited or inhibitory effects of NA, DMV and NTS on the gastric motility by now. To clarify the effects of the three nucleus on gastric motility, our research group has electrically stimulated them respectively and found that they all inhibited gastric motility. Whether excitement of neuron body or excitement of passed fibres conduced to these inhibiting results was unclear. So, in this study, we observed the Fos expression in each neuro-neucleus of the spinal cords and brainstems of rats following RWIS under different times, to discuss the relation between this stress and the excitement of neuro-neucleus in the spinal cords and brainstems of rats.The study included two parts, the experimentⅠa nd the experimentⅡ.The experimentⅠ: the rats were randomly devided into five experimental groups, four rats in each group. In conscious rats, the stress was controlled by employing the RWIS by 0min, 30min, 60min, 120min and 180min respectively. After heart perfusion, the spinal cord and brainstem were removed, and post-fixed overnight, then coronally sliced into 25μm thick of each piece. We used c-Fos immunohistochemistry to characterize neuronal activation of spinal cord and brainstem. There were very few signals for Fos-like immunoreactivities in the spinal cord and brainstem of unstressed rats. But RWIS could induced remarkable c-Fos expression in many parts(NTS, DMV, AP, SubP, LC, PBN, CGO, LRT-PC, et al) of spinal cord and brainstem, furthermore, the number of c-Fos positive nucleus and the intensity of c-Fos expression were different among each parts of the spinal cord and brainstem. Resumptively, the levels of c-Fos expression increased during the beginning time of RWIS and reached a maximum at 60min of stress. But to each nerval nucleus, it is not completely consistent. Fos expression decreased following a long stress time.The experimentⅡ: after bilateral vagotomy beneath diaphragm, rats suffered RWIS for 180min. Then the expression of c-Fos was detected by immunohistochemistry. We found that the Fos expression cut down in brainstem of the rats but boost up in spinal cord of the same rats.The results of this study indicate that RWIS could induced remarkable c-Fos expression in spinal anterior horn and posterior horn and brainstem, the levels of c-Fos expression increased during the beginning time of RWIS and reached a maximum at about 60min of stress. But after bilateral vagotomy beneath diaphragm, Fos expression cut down in brainstem but boost up in spinal cord of rats that suffered RWIS for 180min.