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

Abstract

One of the best known crustacean hormones is the crustacean hyperglycemic hormone (CHH). However, the mechanisms involved in hormone release in these animals 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 glycemic values (C. granulata and O. limosus) and CHH levels (O. limosus) were determined after 2 h in either submerged animals or animals exposed to atmospheric 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 increased from 6.1 to 43.3 and 11.4 mg/100 ml in submerged animals and from 5.7 to 55.2 and 22.5 mg/100 ml in air-exposed animals after treatment with serotonin and fluoxetine, respectively. In O. limosus the increases were from 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 serotonin and fluoxetine, respectively. Serotonin and fluoxetine also caused a significant 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.

Role of biogenic amines and cHH in the crustacean hyperglycemic stress response

“…Moreover, cHH release increases as a function of 5-HT concentration in vivo, and a similar trend was reported in an in vitro system by Escamilla-Chimal et al (2002). In O. limosus, injection of 5-HT caused a significant increase of the circulating level of cHH (Santos et al, 2001).…”

“…Serotonin (5-HT; 5-hydroxytryptamine) is well known as a neurotransmitter in crustaceans on several grounds, and its levels have been measured in the nervous system and hemolymph of various crustacean species (Elofsson et al, 1982;Laxmyr, 1984;Kulkarni and Fingerman, 1992), thus suggesting a possible role as a neurohormone (Rodrigues-Soza et al, 1997). Serotonin has long been known to have a potent hyperglycemic effect in several crustacean species (Bauchau and Mengeot, 1966;Keller and Beyer, 1968;Lee et al, 2000;Lorenzon et al, 1999Lorenzon et al, , 2004aSantos et al, 2001). Lee et al (2001) confirmed the role of 5-HT in mediating the release of cHH.…”

“…Lee et al (2001) confirmed the role of 5-HT in mediating the release of cHH. In the crayfish Orconectes limosus, injection of 5-HT caused a significant increase in the circulating level of cHH (Santos et al, 2001). In P. clarkii, cHH release increased as a dose-related function of 5-HT concentration (Escamilla-Chimal et al, 2002).…”

“…Hyperglycemia is a typical response of many aquatic animals to pollutants. In crustaceans, increased circulating cHH and hyperglycemia are reported to appear during exposure to several environmental stressors (Durand et al, 2000;Lorenzon et al, 1997Lorenzon et al, , 2002Lorenzon et al, , 2004bSantos et al, 2001) in intact, but not eyestalkless animals, suggesting a cHH-mediated response (Fingerman et al, 1981;Reddy et al, 1994Reddy et al, , 1996Lorenzon et al, 2000). In the crab Cancer pagurus, emersion induced an increase in the hemolymph cHH after 4·h (Webster, 1996).…”

Physiological and agonistic behavioural response of Procambarus clarkii to an acoustic stimulus

“…In aquatic animals, hyperglycaemia is a typical stress response to harmful physical and chemical environmental changes, including hypoxia and exposure to air during commercial transport (Spicer et al, 1990;Zou et al, 1996;Kuo and Yang, 1999;Morris and Olivier, 1999;Durand et al, 2000;Speed et al, 2001). Hyperglycaemia has been associated with increased circulating CHH titres (Lorenzon et al, 1997;Lorenzon et al, 2002;Durand et al, 2000;Santos et al, 2001), and has been used as an index to assess CHH activity and environmental stress (Webster, 1996;Bergmann et al, 2001;Toullec et al, 2002). Accordingly, in P. clarkii in the present study, acoustic stress led to a significant increase (P<0.01) in haemolymph glucose levels.…”