YANG, P.-F.; WANG, H.-Y.; LEE, C.-Y.*: Involvement of 5- hydroxytryptamine-enhanced release of crustacean hyperglycemic hormone in stress-induced hyperglycemia

The objectives of the present study were to investigate the effect of 5-hydroxytryptamine (5-HT) on the release of crustacean hyperglycemic hormone (CHH), and to determine if stress-induced hyperglycemia is mediated by 5-HT-enhanced CHH release. Eyestalk ganglia with intact X-organ/sinus gland complex were dissected from the crayfish “Procambarus clarkii” and incubated under various experimental conditions. The incubation media were then analyzed for the presence of released hyperglycemic factor using an in vivo bioassay. The results show that 5-HT enhanced the release of hyperglycemic factor in a dose-dependent manner. The stimulatory effect of 5-HT was significantly decreased by incubating eyestalk ganglia with 5-HT receptor antagonist (ketanserin or methysergide). Activity of the 5-HT-released hyperglycemic factor was reduced by absorption of incubation media with ALPHA-CHH serum, but not by pre-immune or ALPHA-5-HT serum. Furthermore, acute thermal stress (34�C) elicited hyperglycemic responses in animals acclimated to 24�C. The thermal stress-induced hyperglycemia was decreased in reserpine- (a 5-HT depletor) or ketanserin-treated animals. In summary, it is demonstrated that 5-HT enhances release of CHH that in turns elicits hyperglycemic responses. The 5-HT-enhanced CHH release is probably involved in stress-induced hyperglycemia.