PUBLICATION
Transporter-mediated GABA responses in horizontal and bipolar cells of zebrafish retina
- Authors
- Nelson, R., Bender, A.M., and Connaughton, V.P.
- ID
- ZDB-PUB-080501-4
- Date
- 2008
- Source
- Visual neuroscience 25(2): 155-165 (Journal)
- Registered Authors
- Connaughton, Victoria P.
- Keywords
- Outer plexiform layer, ATPase, GABA transporter, Baclofen, Glycine, Horizontal cell, Bipolar cell
- MeSH Terms
-
- Animals
- Dose-Response Relationship, Drug
- Electrophysiology
- GABA Agonists/pharmacology
- GABA Antagonists/pharmacology
- GABA Plasma Membrane Transport Proteins/physiology*
- Glutamic Acid/pharmacology
- In Vitro Techniques
- Membrane Potentials
- Muscimol/pharmacology
- Retinal Bipolar Cells/cytology
- Retinal Bipolar Cells/drug effects*
- Retinal Bipolar Cells/physiology*
- Retinal Horizontal Cells/cytology
- Retinal Horizontal Cells/drug effects*
- Retinal Horizontal Cells/physiology*
- Sodium Chloride/pharmacology
- Zebrafish/physiology*
- gamma-Aminobutyric Acid/administration & dosage
- gamma-Aminobutyric Acid/pharmacology*
- PubMed
- 18442438 Full text @ Vis. Neurosci.
Citation
Nelson, R., Bender, A.M., and Connaughton, V.P. (2008) Transporter-mediated GABA responses in horizontal and bipolar cells of zebrafish retina. Visual neuroscience. 25(2):155-165.
Abstract
GABA-mediated interactions between horizontal cells (HCs) and bipolar cells (BCs) transform signals within the image-processing circuitry of distal retina. To further understand this process, we have studied the GABA-driven membrane responses from isolated retinal neurons. Papain-dissociated retinal cells from adult zebrafish were exposed to GABAergic ligands while transmembrane potentials were monitored with a fluorescent voltage-sensitive dye (oxonol, DiBaC4(5)). In HCs hyperpolarizing, ionotropic GABA responses were almost never seen, nor were responses to baclofen or glycine. A GABA-induced depolarization followed by after hyperpolarization (dep/AHP) occurred in 38% of HCs. The median fluorescence increase (dep component) was 0.17 log units, about 22 mV. HC dep/AHP was not blocked by bicuculline or picrotoxin. Muscimol rarely evoked dep/AHP responses. In BCs picrotoxin sensitive, hyperpolarizing, ionotropic GABA and muscimol responses occurred in most cells. A picrotoxin insensitive dep/AHP response was seen in about 5% of BCs. The median fluorescence increase (dep component) was 0.18 log units, about 23 mV. Some BCs expressed both muscimol-induced hyperpolarizations and GABA-induced dep/AHP responses. For all cells, the pooled Hill fit to median dep amplitudes, in response to treatments with a GABA concentration series, gave an apparent k of 0.61 muM and an n of 1.1. The dep/AHP responses of all cells required both extracellular Na+ and Cl(-), as dep/AHP was blocked reversibly by Li+ substituted for Na+ and irreversibly by isethionate substituted for Cl(-). All cells with dep/AHP responses in zebrafish have the membrane physiology of neurons expressing GABA transporters. These cells likely accumulate GABA, a characteristic of GABAergic neurons. We suggest Na+ drives GABA into these cells, depolarizing the plasma membrane and triggering Na+, K+-dependent ATPase. The ATPase activity generates AHP. In addition to a GABA clearance function, these large-amplitude transporter responses may provide an outer plexiform layer GABA sensor mechanism.
Genes / Markers
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Orthology
Engineered Foreign Genes
Mapping