Molecular and pharmacological properties of GABA-rho subunits from white perch retina

J Neurobiol. 1998 Nov 5;37(2):305-20. doi: 10.1002/(sici)1097-4695(19981105)37:2<305::aid-neu9>;2-6.


Five gamma-aminobutyric acid (GABA)-rho subunits were cloned from a white perch retinal cDNA library and expressed in Xenopus oocytes. The deduced amino acid sequences indicated that all are highly homologous to the GABA-rho subunits cloned from mammalian retinas; two clones (perch-rho 1A and perch-rho 1B) were in the rho 1 family, two (perch-rho 2A and perch-rho 2B) were in the rho 2 family, and one clone has been tentatively identified as a perch-rho 3 subunit. When expressed in Xenopus oocytes, all but one of the subunits (rho 3) formed functional homooligomeric receptors. However, the receptors expressed by each of the GABA-rho subunits displayed unique response properties that distinguished one from the other. For example, receptors formed by perch-rho 1B subunits were more sensitive to GABA than the receptors formed by other GABA-rho subunits, the dose-response curves for the various receptors revealed different Hill coefficients, and there were differences in the kinetics of the GABA-induced currents. In addition, the GABA-mediated current-voltage curve for rho 2 receptors was approximately linear, whereas the responses from rho 1 receptors showed outward rectification. A further division in the properties of the GABA-rho subunits was revealed in their responses to imidazole-4-acetic acid (I4AA); the drug behaved as an antagonist on A-type rho receptors and a partial agonist on the B-type rho receptors. These results suggest that there is a large diversity of GABAC receptors in the vertebrate retina, probably formed by homooligomeric and heterooligomeric combinations of GABA rho subunits, that exhibit different functional properties.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cloning, Molecular
  • Female
  • GABA Antagonists / pharmacology
  • Gene Library
  • Kinetics
  • Molecular Sequence Data
  • Oocytes / metabolism
  • Perches / metabolism*
  • Picrotoxin / pharmacology
  • Receptors, GABA-A / classification
  • Retina / chemistry*
  • Sequence Homology, Amino Acid
  • Xenopus
  • Zinc / pharmacology
  • gamma-Aminobutyric Acid / chemistry
  • gamma-Aminobutyric Acid / pharmacology*


  • GABA Antagonists
  • Receptors, GABA-A
  • Picrotoxin
  • gamma-Aminobutyric Acid
  • Zinc

Associated data

  • GENBANK/AF101034
  • GENBANK/AF101035
  • GENBANK/AF101036
  • GENBANK/AF101037