Studies Of Effects Of Psychological Stress On The Expression Of Metallothioneins In Brain And The Related Mechanisms

The present studies were conducted to evaluate the effects of psychological stress on the expression of metallothioneins in different domains of brain in Wistar rats. And the regulating roles of metal zinc to play in the expression of metallothioneins were also explored, both in brain and in cultured hippocampus neurons.The animal model of psychological stress was developed by restraint. The Wistar rats were randomly assigned to four groups as follows: control group and three stress groups that received restraint treatment one, two or four weeks respectively. The results suggested that restraint stress can impair the normal histology of hippocampus and its biological functions. Compared with the control group, the stressed rats have increased contents of metallothioneins in cerebrum and hippocampus. And the levels of MT-lmRNA and MT-3mRNA were also elevated significantly in hippocampus. Furthermore, there is positive relationship between the expression of metallothioneins and the period of stress. To evaluate the effects of zinc on the expression of metallothioneins in different domains of brain, the rats were fed with different contents of zinc forages. The results indicated that zinc-deficient rats have a low level of metallothioneins in hippocampus, ar chipallium, cortex and diencephalons, whereas the metallothioneins' expression in zinc-deficient stressed rats was increased dramatically. The levels of plasma glucocorticoids, interleukin-6, interleukin-1 and nitric oxide were increased obviously in stressed rats.The neurons of hippocampus were cultured for 24h with glucocorticoids to produce the stress model of cells. It showed that the metallothioneins' expression in stressed cells was enhanced clearly in contrast to that of non-stressed cells. We got the zinc-deficient cells by adding TPEN, a zinc-specialized chelator, to culture medium. The results showed that the expression of metallothioneins decreased in zinc-deficient hippocampal neurons.Above all, psychological stress can enhance the expression of metallothioneins in brain of rats. Metal zinc is one of the important factors to regulate metallothioneins' production, and its functions may be correlated with glucocorticoids, cytokines and nitric oxide in the procedure. The nutritional status of zinc may be very crucial in the reply of body to psychological stress, and zinc deficiency can impair the body's adaptation to stress.