Related Experiment Videos
Allosteric modulation of [35S]TBPS-binding in the cerebral cortex of the rat during postnatal development
O Giorgi1, E Cancedda, D Lecca
1Department of Toxicology, University of Cagliari, Italy.
Insights
The study reveals how GABA-gated chloride channels develop in rat brains. GABA levels influence binding site density and affinity during early development, impacting receptor function.
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- The GABA-gated chloride channel is crucial for inhibitory neurotransmission in the central nervous system.
- Understanding its developmental trajectory is key to comprehending brain maturation and function.
Purpose of the Study:
- To investigate the ontogenesis of the GABA-gated chloride channel in the rat cerebral cortex.
- To examine the impact of endogenous GABA levels on [35S]TBPS binding site development.
Main Methods:
- Monitoring [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding parameters in rat cerebral cortex membranes at various postnatal ages (1-90 days).
- Comparing binding assays in unwashed membranes (reflecting endogenous GABA) versus washed membranes (with exogenous GABA).
Main Results:
- GABA-gated chloride channel binding site density increased significantly within 10 days post-birth, with a greater increase observed in washed membranes.
- The affinity of [35S]TBPS for binding sites remained constant in washed membranes but increased with age in unwashed membranes.
- Developmental changes in endogenous GABA content influenced [35S]TBPS binding site density and affinity.
Conclusions:
- Endogenous GABA levels play a significant role in modulating the developmental expression of GABA-gated chloride channels.
- These findings provide insights into the maturation of inhibitory neurotransmission during early brain development.
Abstract:
The ontogenesis of the GABA-gated Cl- channel was investigated in the cerebral cortex of the rat by monitoring the binding parameters of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) at intervals after birth (1-90 days). To investigate the influence of the developmental changes in the content of GABA on [35S]TBPS-binding, the assays were carried out in unwashed membranes, in which the concentration of GABA was dependent on its content in vivo, and in repeatedly washed membranes in the presence of defined concentrations of exogenous GABA. At birth, the density (Bmax) of [35S]TBPS-binding sites in unwashed membranes was similar to that found in well-washed membranes. However, in unwashed membranes, the number of [35S]TBPS-binding sites increased by two-fold within 10 days after birth whereas in washed membranes it increased by four-fold during the same period. The higher density of [35S]TBPS-binding sites in washed membranes as compared with the unwashed counterparts persisted throughout development. In unwashed membranes, the apparent Kd for [35S]TBPS-binding increased with age whereas in washed membranes the affinity of [35S]TBPS for its binding sites remained constant throughout development. The binding of [35S]TBPS to the GABA-gated Cl- channel is allosterically modulated by drugs acting on different sites of the GABAA receptor complex. Thus, GABA and diazepam decrease [35S]TBPS-binding whereas the GABAA receptor antagonist, bicuculline, and the inverse agonist for benzodiazepine receptors, 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylic acid methyl ester, increase it.(ABSTRACT TRUNCATED AT 250 WORDS)