PUBLICATION
Flumazenil-insensitive benzodiazepine binding sites in GABAA receptors contribute to benzodiazepine-induced immobility in zebrafish larvae
- Authors
- Cao, Y., Yan, H., Yu, G., Su, R.
- ID
- ZDB-PUB-191108-33
- Date
- 2019
- Source
- Life sciences 239: 117033 (Journal)
- Registered Authors
- Keywords
- GABA(A) receptor, benzodiazepine, immobility, nonclassical binding site, zebrafish
- MeSH Terms
-
- Animals
- Azides/pharmacology
- Benzodiazepines/metabolism*
- Benzodiazepines/pharmacology*
- Benzodiazepines/toxicity
- Bicuculline/pharmacology
- Binding Sites/drug effects
- Clonazepam/pharmacology
- Dose-Response Relationship, Drug
- Female
- Flumazenil/pharmacology*
- Flumazenil/toxicity
- GABA Antagonists/pharmacology
- GABA Modulators/pharmacology*
- GABA Modulators/toxicity
- Larva
- Male
- Motor Activity/drug effects*
- Receptors, GABA-A/drug effects*
- Zebrafish
- PubMed
- 31697950 Full text @ Life Sci.
Citation
Cao, Y., Yan, H., Yu, G., Su, R. (2019) Flumazenil-insensitive benzodiazepine binding sites in GABAA receptors contribute to benzodiazepine-induced immobility in zebrafish larvae. Life sciences. 239:117033.
Abstract
Aims Benzodiazepines (BZDs) produce various pharmacological actions by binding to and allosterically regulating GABAA receptors. Several in vitro studies have demonstrated diazepam, the prototypic BZD, produces a high-dose action that cannot be countered with the classical BZD-binding site antagonist flumazenil. Here, we investigate the existence and behavioral relevance of non-classical BZD binding sites in zebrafish larvae.
Main methods Zebrafish larvae were treated with a series of BZDs alone or combined with flumazenil, bicuculline (a non-selective GABAA receptor antagonist), or RO 15-4513 (a general BZD antagonist and a proposed antagonist interacting with α+/β- interfaces in α4/6/β3δ receptors), and their locomotor activities and behavioral phenotypes were recorded.
Key findings Diazepam-induced hypolocomotion (sedation-like state) at low doses (10 and 20 mg L-1) was effectively antagonized by flumazenil or bicuculline, while diazepam-induced immobility (anesthesia-like state) at higher dose (30 mg L-1) was prevented by bicuculline (3 mg L-1) but not flumazenil, even at doses up to 150 mg L-1. Ro 15-4513 also failed to efficiently antagonize diazepam-induced immobility. Immobility induced by high dose of another 1,4-BZD, clonazepam, was also resistant to flumazenil.
Significance These results provide direct in vivo evidence for non-classical BZD-binding sites, which may be located at the second transmembrane domain of GABAA receptors and contribute to BZD-induced anesthesia.
Genes / Markers
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Orthology
Engineered Foreign Genes
Mapping