ZFIN ID: ZDB-PUB-051012-10
Characterization of Opioid-Binding Sites in Zebrafish Brain
Gonzalez-Nuñez, V., Barrallo, A., Traynor, J.R., and Rodriguez, R.E.
Date: 2006
Source: The Journal of pharmacology and experimental therapeutics   316(2): 900-904 (Journal)
Registered Authors: Barrallo Gimeno, Alejandro, González Nuñez, Veronica, Rodriguez, Raquel E.
Keywords: none
MeSH Terms:
  • Animals
  • Benzomorphans/pharmacology*
  • Binding, Competitive*
  • Brain/drug effects
  • Brain/metabolism*
  • Diprenorphine/pharmacology*
  • Female
  • In Vitro Techniques
  • Ligands
  • Male
  • Narcotic Antagonists/pharmacology*
  • Radioligand Assay
  • Receptors, Opioid/metabolism*
  • Zebrafish
PubMed: 16207834 Full text @ J. Pharmacol. Exp. Ther.
The pharmacological profile of opioid-binding sites in zebrafish brain homogenates has been studied using radiolabelled binding techniques. The non-selective antagonist [(3)H]-diprenorphine binds with high affinity (KD = 0.27 +/- 0.08 nM and a Bmax = 212 +/- 14.3 fmol /mg protein), displaying two different binding sites with affinities of KD1= 0.08 +/- 0.02 nM and KD2= 17.8 +/- 9.18 nM. The non-selective agonist [(3)H]-bremazocine also binds with high affinity to zebrafish brain membranes, but only displays one single binding site with a KD= 1.1 +/- 0.09 nM and a Bmax = 705 +/- 19.3 fmol/mg protein. Competition binding assays using [(3)H]-diprenorphine and several unlabelled ligands were performed. The synthetic selective agonists for mammalian opioid receptors DPDPE, DAMGO and U69,593 failed to effectively displace [(3)H]-diprenorphine binding, while non-selective ligands and the endogenous opioid peptides such as dynorphin A showed good affinities in the nanomolar range, although several of the endogenous peptides only displaced approximately 50% of the specifically bound [(3)H]-diprenorphine. Our results provide evidence that, although the selective synthetic compounds for mammalian receptors do not fully recognise the opioid binding sites in zebrafish brain, the activity of the endogenous zebrafish opioid system might not significantly differ from that displayed by the mammalian opioid system. Hence the study of zebrafish opioid activity may contribute to an understanding of endogenous opioid systems in higher vertebrates.