Decrease of ACh response in isolated duodenum from SART stressed (repeated cold stressed) mice

Abstract

ACh response in the isolated duodenum from SART stressed (repeated cold stressed) mice was remarkably decreased in comparison to normal mice 5 days after onset of loading SART stress, and maximal contraction in SART stress mice duodenum was about 37% of that in non-stressed mice. Pilocarpine and KCl responses were also considerably decreased, but BaCl₂ response was much the same as in the controls. Thus, the contraction system of the muscle is apparently not damaged by SART stress. Though body weights decreased, the daily intake of food increased in SART stressed mice. Length of small intestine from SART stressed mice was much the same as in controls, but wet weights of small intestines were larger than in controls. Autonomic agonists, antagonists, tranquilizers and other drugs were given intraperitoneally to mice once daily during SART stress, and the ACh responses in the isolated duodenum were investigated. Pretreatment with adrenergic and anticholinergic drugs inhibited the decrease of ACh response, but antiadrenergic and cholinergic drugs had no effects. Pretreatment with tranquilizers such as reserpine, chlorpromazine, carpipramine and imipramine inhibited the decrease of ACh response in the isolated duodenum, but diazepam, meprobamate and benadryl had no influence. Pretreatment of neurotropin, a neurosedative had good inhibitory effects. Our results suggest that SART stressed mice may be in a state of unbalance regarding sympathetic and parasym pathetic nerves, particularly with regard to abnormal tension in the parasympathetic nervous system, in part of the duodenum. Pretreatment with most of the above drugs had no influence on loss of body weight in SART stressed mice while pretreatment with neurotropin inhibited body weight to a considerable extent.