Immunohistochemical Study for Expression of cFos-like Protein Induced by Acute Hypotension in Rat Brain

ABSTRACT

BACKGROUND: It has been well known that cFos protein, one of the immediate-early gene proteins, was a cellular marker to characterize physiological or anatomical property of neural networks in mammalian brain. The purpose of this study was to evaluate quantitative change of cFos protein expression in rat brain nuclei concerned with regulation of blood pressure according to severity of hypotension and compare the spatial pattern of cFos between hemorrhagic hypotension and non-hemorrhagic hypotension elicited by vasodilatation. METHODS: The mean blood pressure (MBP) in the femoral artery was recorded by using pressure transducer and polygraph. Nitroprusside was injected into the femoral vein with constant flow rate by means of osmotic pump in which the dosage was 5microgram Per kg a minute. Immunohistochemical staining was Performed by using conventional ABC method to visualize cFos-like immunoreactive (cFLI) neurons in many brain nuclei and FLI cells were counted by image analyser. RESULTS: Mild hemorrhage group with MBP of 70-80 mmHg showed significant increase of cFLI expression in the paraventricular nuclei and supraoptic nuclei. In contrast, severe hemorrhage group with MBP of 50 mmHg increased significantly cFLI expression in the rostral ventrolateral medulla, periventricular thalamic nucleus, central gray matter, medial vestibular nuclei as well as the nuclei seen in mild hemorrhage group. Nitroprusside induced hypotension exhibited a similar spatial pattern of ctrl expression to severe hemorrhage group. CONCLUSION: These results suggest that severe reduction of blood pressure induces expression of cFLI neurons in the neural network systems that control vital organs.