Mechanism of painful breast induced by cold stimulus Yoshinori ITOH (Nagoya) Dept. of Physiol., Nagoya Univ, Sch, of Med., Nagoya, Japan Abstract Cold colic pain response was first mentioned in Kinkiyoryaku, a famous classic of chinese medicine. I had defined it as durable, severe, abdominal pain induced by cold stintulus and cured by warming on the basis of the text and a clinical case. The characteristics of the cases which satisfied the criteria were as follows. (1) Woman of ovarian hypofunction has a tendency to be attacked episodically related to cold stimulus, cold adaptation and menstruation. (2) There is a latency from the onset or end of cold stimulus to the beginning of the abdominal pain. (3) Lower abdomen has a lower threshold of the response than the upper abdomen. (4) The characteristics of the abdominal pain suggest that they arise from severe contraction of smooth muscles of gastrointestinal canal or uterus. I collected four cases of painful breast induced by cold, and speculated that a cold stressor released oxytocin and vasopressin from the posterior lobe and they caused painful contraction of mammary myoepithelium. The characteristics of cold colic response suggest that oxytocin and vasopressin cause painful contraction of uterus or gastrointestinal canal. Therefore, I speculate that both cold colic pain response and painful breast induced by cold have a common mechanism. That is, cold stressor releases oxytocin and vasopressin from the posterior lobe, and these hormones cause painful contraction of mammary myoepithelium and smooth muscles of uterus and gastrointestinal canal. Usually, painful breast and abdominal pain do not coexist. This organ selection seems to depend on local factors. Locally applied cold stimulus facillitate contraction of the organ. Stretch of myoepithelium by stored milk lowers the threshold of pain caused by the contraction. And uterus is apt to contract during postpartum and postmenstrual period.
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