Effect of intermaxillary fixation (IMF) on rat brain noradrenaline turnover

Abstract

This study was carried out to investigate the effects of intermaxillary fixation (IMF) on noradrenalin (NA) release in the rat brain regions by measuring a major metabolite of brain NA, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO₄) levels in the regions and plasma corticosterone levels. Male Wistar rats were anesthetized with pentobarbital and IMF was performed. Control rats were only anesthetized.
The rats were decapitated 4h, 12h, and 24h after IMF. Weights of spleen, thymus, and adrenal gland were measured only in the rats with or without IMF at 24h. Levels of MHPG-SO₄ in the IMF rats were significantly increased in the LC region (4h, 24h), hypothalamus (4h, 12h, 24h), cerebral cortex (4h, 12h, 24h), amygdala (4h, 12h), hippocampus (4h), pons +med. oblongata excluding the LC (4h, 12h, 24h), and midbrain (12h, 24h) as compared to those of the respective control rats. Plasma corticosterone levels were significantly increased by IMF throughout the courses of time. Organ weights in the IMF rats were significantly decreased in the thymus and spleen, and significantly increased in the adrenal glands. These results suggest that IMF could be stressfull for the rats and activates the central NA neuronal system.