Serotonergic regulation of blood glucose levels in the crayfish,Procambarus clarkii: Site of action and receptor characterization
✍ Scribed by Lee, Chi-Ying; Yau, Shiou-Mei; Liau, Ching-Sheyen; Huang, Wen-Jr
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 145 KB
- Volume
- 286
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
The present study investigated the site of action of 5-hydroxytryptamine (5-HT) and pharmacologically characterized the receptors involved in regulating blood glucose levels in the crayfish, Procambarus clarkii. Injection of 5-HT into intact animals increased glucose levels in a dose-dependent manner. In contrast, 5-HT failed to elicit a hyperglycemic response in eyestalkablated animals. Effects of several 5-HT receptor agonists and antagonists were examined. 5-CT, oxymetazoline (both 5-HT 1 receptor agonists) and α-methyl-5-HT (a 5-HT 2 receptor agonist), but not 1-phenylbiguanide, m-CPBG (both 5-HT 3 receptor agonists), or RS 67333 (a 5-HT 4 receptor agonist), induced hyperglycemic responses in a dose-dependent manner. In addition, 8-OH-DPAT (a 5-HT 1A receptor agonist), L-694,247 (a 5-HT 1B/1D receptor agonist), and DOI (a 5-HT 2A receptor agonist) were effective in significantly increasing the glucose levels, whereas both BW 723C86 (a 5-HT 2B receptor agonist) and m-CPP (a 5-HT 2C receptor agonist) were ineffective. Finally, ketanserin (a 5-HT 2A receptor antagonist), but not p-MPPF (a 5-HT 1A receptor antagonist), GR 55562 (a 5-HT 1B/1D receptor antagonist), SB 206553 (a 5-HT 2B/2C receptor antagonist), or tropisetron (a 5-HT 3 receptor antagonist), was able to block 5-HT-induced hyperglycemia. The combined results support the hypothesis that 5-HT exerts its hyperglycemic effect by enhancing the release of hyperglycemic factor(s) from the eyestalks, and suggest that 5 HT-induced hyperglycemia is mediated by 5-HT 1 -and 5-HT 2 -like receptors.