The contractile response to acetylcholine (ACh) of the isolated duodenum from the restraint and water immersion stressed (RWIS) mouse was found to be enhanced by the stress for 1 hr and reach a maximum in 3 hr stress followed by a decrease. It was clarified that this rise in the response is not due to the change in the affinity to ACh but due to the increase of the intrinsic activity. The contractile response to KCl was augmented only when concentration of KCl was high, while the response to BaCl₂ was little enhanced in the stressed animal. The relaxing response to noradrenaline (NA) of the isolated duodenum from rat, on the other hand, was reduced by the stress. Such reduced response to NA was observed to be more marked than the enhanced response to ACh in the vas deferens isolated from the stressed animal. The pretreatment to the RWIS mouse with either antiadrenergic or cholinergic drugs resulted in the clear-cut blockade of the enhancement of response to ACh of the isolated duodenum from this animal. These results contrasted to the effects on the reduced response to ACh of the isolated duodenum from the SART stressed (repeated cold stressed) mouse. The pre-administration of psychotropic drugs showed marked suppression on the enhancement of response of the duodenum of the RWIS animal, though there was a quantitative difference between the RWIS and SART animals. The pretreatment with a neurosedative, Neurotropin^[○!R](NSP) was also found to show similarly marked suppressive action. From these results, it was considered that the duodenum and the vas deferens of the RWIS animal are in the state of the sympathicotonia, namely partial sympathicotonia.