title: 5-HT receptors as novel targets for optimizing pigmentary responses in dorsal skin melanophores of frog, Hoplobatrachus tigerinus.
abstract: OBJECTIVE
  Biochemical identification of 5-HT has revealed similar projection patterns across vertebrates. In CNS, 5-HT regulates major physiological functions but its peripheral functions are still emerging. The pharmacology of 5-HT is mediated by a diverse range of receptors that trigger different responses. Interestingly, 5-HT receptors have been detected in pigment cells indicating their role in skin pigmentation. Hence, we investigated the role of this monoaminergic system in amphibian pigment cells, melanophores, to further our understanding of its role in pigmentation biology together with its evolutionary significance.
  
  
  METHODS
  Pharmacological profiling of 5-HT receptors was achieved using potent/selective agonists and antagonists. In vitro responses of melanophores were examined by Mean Melanophores Size Index assay. The melanophores of lower vertebrates are highly sensitive to external stimuli. The immediate cellular responses to drugs were defined in terms of pigment translocation within the cells.
  
  
  RESULTS
  5-HT exerted strong concentration-dependent pigment dispersion at threshold dose of 1 × 10(-6) g·mL(-1). Specific 5-HT(1) and 5-HT(2) receptor agonists, sumatriptan and myristicin. also induced dose-dependent dispersion. Yohimbine and metergoline synergistically antagonized sumatriptan-mediated dispersion, whereas trazodone partially blocked myristicin-induced dispersion. Conversely, 5-HT(3) and 5-HT(4) receptor agonists, 1 (3 chlorophenyl) biguanide (1,3 CPB) and 5-methoxytryptamine (5-MT), caused a dose-dependent pigment aggregation. The aggregatory effect of 1,3 CPB was completely blocked by ondansetron, whereas L-lysine partially blocked the effect of 5-MT.
  
  
  CONCLUSIONS
  The results suggest that 5-HT-induced physiological effects are mediated via distinct classes of receptors, which possibly participate in the modulation of pigmentary responses in amphibian.
authors: Department of Biotechnology, Saifia College of Science, Bhopal, India. drshariqueali@yahoo.co.in
authors: Sharique A
authors: SA
authors: Ali
authors: Saima
authors: S
authors: Salim
authors: Tarandeep
authors: T
authors: Sahni
authors: Jaya
authors: J
authors: Peter
authors: Ayesha S
authors: AS
authors: Ali
mesh_terms: D000818:Animals; D001001:Anura; D008547:Melanophores / Q000187:drug effects* / Q000378:metabolism*; D058990:Molecular Targeted Therapy; D010860:Pigments, Biological / Q000378:metabolism; D011985:Receptors, Serotonin / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D012867:Skin / Q000187:drug effects* / Q000378:metabolism*; D012880:Skin Pigmentation / Q000187:drug effects* / Q000502:physiology*
chemical_list: D010860:Pigments, Biological; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin