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Memory modulation by brain benzodiazepines
I Izquierdo1, J H Medina, C Da-Cunha
1Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil.
Summary
Endogenous benzodiazepines and GABA-A systems in the brain down-regulate memory consolidation. Blocking these systems post-training enhances memory retention for habituation and avoidance learning.
Area of Science:
- Neuroscience
- Memory Consolidation
- Neuropharmacology
Background:
- Post-training memory processes are regulated by benzodiazepine/GABA-A systems in the amygdala, septum, and hippocampus.
- Decreased benzodiazepine-like immunoreactivity during learning suggests endogenous benzodiazepine release.
- Memory retention is modulated by these neurochemical systems.
Purpose of the Study:
- To investigate the role of endogenous benzodiazepine/GABA-A systems in memory down-regulation.
- To elucidate the mechanism of action of these systems in the amygdala.
- To determine the impact of modulating these systems on memory retention.
Main Methods:
- Microinjection of benzodiazepine antagonist flumazenil into the hippocampus and amygdala.
- Administration of GABA-A receptor modulators (muscimol, picrotoxin, Ro5-4864) in the amygdala.
- Utilizing habituation and avoidance learning paradigms in rodents.
Main Results:
- Post-training flumazenil administration enhanced retention of habituation and avoidance learning.
- Endogenous benzodiazepine release increased GABA-A receptor sensitivity to muscimol in the amygdala.
- Blocking GABA-A receptors with picrotoxin or Ro5-4864 post-training enhanced memory retention.
Conclusions:
- Endogenous benzodiazepine/GABA-A mechanisms down-regulate memory consolidation in the amygdala, septum, and hippocampus.
- These memory-down-regulating systems are activated by task-associated anxiety and stress.
- Memory lability during consolidation is a consequence of the brain's response to stress.