“Transient acetylcholinosis”. Cause of Chinese Restaurant syndrome

Both clinical data and biochemical findings in our stuidies suggest that the signs and symptoms following monosodium glutamate (MSG) ingestion represent “transient acetylcholinosis.” Dose-related reactions occurred in 14 volunteers after MSG ingestion on empty stomach, including numbness of neck, heaviness of eyelids and legs, lacrimation, headache, nausea, urgency of urination and defecation, drowsiness, substernal pressure, abdominal discomfort, palpitations and colicky pain. The protean nature of the symptoms, the mode of appearance and recovery, variations in severity, all were remarkably similar to the diffuse, evanescent action of acetylcholine (ACh). In 4 subjects primed with atropine, there was blockage of symptoms even though MSG dose was doubled. On the other hand, prostigmine ( 1 3 usual dose) given with MSG markedly6 exacerbated symptoms in 4 subjects tested. Others have shown that glutamate is a suitable substrate for ACh synthesis. In 10 subjects receiving 150 MSG/kg body wt., cholinesterase (ChE) was measured at 0, 20, 40, 60, 90, 150, and 180 minutes. At 60 min., there was a drop of 30% below baseline. A significantly sharper drop was observed when prostigmine was administered simultaneously with MSG. On the other hand, control tests with histidine showed no fluctuation beyond 5%. Following infusion of ACh into a dog, the pattern of ChE activity was strikingly similar to that observed in man following MSG ingestion. Clinical response to ACh also paralleled human symptoms, except for severity. In 2 infants with Down's Syndrome, ChE chnages after MSG also followed the pattern seen in adult volunteers. Juding by this criterion infants do develop Chinese Restaurant Syndrome following MSG ingestion.