Distribution of GABA(C)-like responses among acutely dissociated rat retinal neurons

Vis Neurosci. Jan-Feb 1999;16(1):179-90. doi: 10.1017/s0952523899161133.

Abstract

GABAergic responses of acutely dissociated rat retinal neurons, including both bipolar cells (BCs) and other, morphologically round cells (RCs), were assayed with the fluorescent (FL), voltage-sensitive probe oxonol DiBaC4(5). Using intensified video microscopy and simultaneous recording, GABA responses were identified in one-third of cells in a typical microscope field; of these 85% hyperpolarized (0.05-0.3 log unit FL decreases) while the remainder depolarized (0.05-0.2 log unit FL increases). GABA-sensitive cells were also TACA-sensitive (trans-4-Aminocrotonic acid), and these ligands appeared interchangeable in ability to evoke responses. In RCs, an asymmetric co-responsive pattern was observed between GABA- and muscimol-evoked events. Muscimol-sensitive RCs responded well to GABA, but not all GABA-sensitive RCs responded to muscimol. In GABA-sensitive BCs, muscimol responses were typically weak or absent. Few BCs or RCs responded to CACA (cis-4-Aminocrotonic acid). Bicuculline-resistant GABA responses occurred in approximately 80% of GABA-responsive RCs and BCs. Both bicuculline-sensitive (GABA(A)-like) and bicuculline-insensitive (GABAc-like) responses were resistant to picrotoxin. Although a small minority of GABA-sensitive cells hyperpolarized in response to R(+)baclofen, bicuculline-insensitive responses were not antagonized by 2-hydroxysaclofen, and were abolished in low [Cl-]o. Results suggested (1) that bicuculline-insensitive, Cl(-)-dependent, GABAc-like responses were broadly distributed and predominant among dissociated rat retinal neurons; (2) that muscimol was a particularly weak agonist for rat retinal BCs; and (3) that oxonol was a sensitive probe for retinal GABA responses.

MeSH terms

  • Animals
  • Barbiturates / metabolism
  • Fluorescent Dyes / metabolism
  • GABA Agonists / pharmacology
  • GABA Antagonists / pharmacology
  • Interneurons / metabolism
  • Isoxazoles / metabolism
  • Neurons / drug effects
  • Neurons / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA / metabolism
  • Retina / drug effects
  • Retina / metabolism*
  • gamma-Aminobutyric Acid / metabolism*

Substances

  • Barbiturates
  • Fluorescent Dyes
  • GABA Agonists
  • GABA Antagonists
  • Isoxazoles
  • Receptors, GABA
  • bis(1,3-dibutylbarbiturate)trimethine oxonol
  • gamma-Aminobutyric Acid