Serotonergic regulation of blood glucose levels in the crayfish, Procambarus clarkii: site of action and receptor characterization.
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 eyestalk-ablated animals. Effects of several 5-HT receptor agonists and antagonists were examined. 5-CT, oxymetazoline (both 5-HT(1) receptor agonists) and alpha-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.
Lee
C Y
CY
Department of Biology, National Changhua University of Education, Changhua, Taiwan 50058, Republic of China. bicylee@cc.ncue.edu.tw
Yau
S M
SM
Liau
C S
CS
Huang
W J
WJ
D000818:Animals; D060829:Arthropod Proteins; D003400:Astacoidea / Q000378:metabolism*; D001786:Blood Glucose / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006943:Hyperglycemia / Q000139:chemically induced* / Q000378:metabolism; D007447:Invertebrate Hormones / Q000378:metabolism; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010109:Oxymetazoline / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
D060829:Arthropod Proteins; D001786:Blood Glucose; D007447:Invertebrate Hormones; D009419:Nerve Tissue Proteins; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C015947:hyperglycemic hormone, crustacean; D012701:Serotonin; D010109:Oxymetazoline