Study of the biochemical processing of the biowarning information through the hypothalamu

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This study was designed to study the dynamic changes in serotonin (5HT) and noradrenaline (NA) levels during the stressful stimuli, and have reached the following conclusions in rats. (1) Immobilization-stress caused anorexia in conjunction with an immediate increase in thehypothalamic 5HT release. Injection of 5HT receptor antagonist significantly reduced the immobilization-induced anorexia, suggesting that the hypothalamic serotonergic ystem is activated during stress and 5HT is an inhibitory transmitter in feeding behavior. (2) Immobilization elevated NA levels in the medial prefrontal cortex (PFC). Pre-injection of a benzodiazepine receptor agonist, diazepam, significantly attenuated the immobilization-induced NA release, while the injection of an anxiogenic compound, FG7142, facilitated it in non-stressed condition. Thus the stressfull stimuli activate the NA system in the medial PFC which may be modulated by an activation of the benzodiazepine receptors in the brain. (3) Immobilization-stress rapidly increased NA levels of spleen in conjunction with the suppression of natural killer (NK) cytotoxicity. Both theincreased levelsof NA ad he suppresion of NK cytotoxicity were significantly attenuated after surgical denervation of the splenic sympathetic nerve, indicating that immobilization-induced suppression of splenic N/K cytotoxicity was mediated predominantly through enhanced activity of the splenic sympathetic nerve..These results suggest that both 5HT and NA may act asneurotransmitters and/or neuromodlators which regulate biowarning processes in the living body.