Effects of serotonin and fluoxetine on blood glucose regulation in two decapod species

of the best known crustacean hormones is the crustacean hyperglycemic hormo ne (CHH). However, the mechanisms involved in hormone release in these anim als are poorly understood, and thus constitute the central objective of the present study. Different groups of crustaceans belonging to diverse taxa ( Chasmagnathus granulata, a grapsid crab and Orconectes limosus, an astacid) were injected with serotonin, fluoxetine, or a mixture of both, and glycem ic values (C. granulata and O. limosus) and CHH levels (O. limosus) were de termined after 2 h in either submerged animals or animals exposed to atmosp heric air. Both serotonin and fluoxetine caused significant hyperglycemia ( P<0.05) after injection into the blood sinus of the two species, an effect enhanced after exposure to atmospheric air. In C. granulata blood glucose i ncreased from 6.1 to 43.3 and 11.4 mg/100 mi in submerged animals and from 5.7 to 55.2 and 22.5 mg/100 mi in air-exposed animals after treatment with serotonin and fluoxetine, respectively. In O. limosus the increases were fr om 1.2 to 59.7 and 135.2 mg/100 ml in submerged animals and from 2.5 to 200 .3 and 193.6 mg/100 ml in air-exposed animals after treatment with serotoni n and fluoxetine, respectively. Serotonin and fluoxetine also caused a sign ificant increase in the circulating levels of CHH in O. limosus, from 11.9 to 43 and 45.7 fmol/ml in submerged animals and from 13.2 to 32.6 and 45.7 fmol/ml in air-exposed animals, respectively, thus confirming their action as neuroregulators in these invertebrates.