The hypoglycaemic effect of 5-hydroxytryptophan.

1 In nialamide-treated mice, L-5-hydroxytryptophan produced a dose-dependent hypoglycaemic response which was independent of whether the animals had been fed or fasted.2 This response was accompanied by a head-twitching response which was also dose-dependent.3 The hypoglycaemic response was not accompanied by an elevation in plasma immunoreactive insulin levels and was fully manifest in alloxan diabetic animals.4 5-Hydroxytryptophan did not increase the in vitro glucose uptake of adipose tissue or skeletal muscle, either on incubation of the tissues in contact with the drug or on incubation of tissues removed from mice injected with the drug.5 Both the hypoglycaemic and head-twitching responses were prevented by pretreatment with methysergide or cyproheptadine and augmented by mepyramine treatment.