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Published on: August 20, 2020
Memory extinction requires gene expression in rat hippocampus
Monica R Vianna1, Lionel Muller Igaz, Adriana S Coitinho
1Centro de Memória, Departamento de Bioqui;mica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, 90035-003, RS, Porto Alegre, Brazil. mrmvianna@yahoo.com <mrmvianna@yahoo.com>
Insights
Gene transcription and protein synthesis are crucial for memory extinction in rats. Inhibiting these processes during initial retrieval prevents the loss of conditioned avoidance responses.
Area of Science:
- Neuroscience
- Molecular Biology
- Behavioral Science
Background:
- Inhibitory avoidance learning is a key model for studying memory.
- Extinction of learned responses involves new learning and synaptic plasticity.
Purpose of the Study:
- To investigate the molecular mechanisms underlying the extinction of conditioned responses.
- To determine the role of gene transcription and protein synthesis in memory extinction.
Main Methods:
- Rats underwent inhibitory avoidance training and extinction trials.
- Infusions of gene transcription inhibitors (DRB, alpha-amanitin) and a protein synthesis inhibitor (anisomycin) were administered into the dorsal hippocampus.
- Behavioral responses, general activity, and anxiety levels were assessed.
Main Results:
- Inhibitors of gene transcription and protein synthesis blocked the extinction of the conditioned response.
- These effects were observed when drugs were administered before the first extinction trial, but not hours after.
- Drug treatments did not affect memory retrieval, general activity, or anxiety.
Conclusions:
- Gene transcription and protein synthesis are essential for the process of memory extinction.
- These molecular processes are required during the initial phase of extinction retrieval.
- The findings support the role of new synaptic associations in memory extinction.
Abstract:
Rats with cannulae in the dorsal CA1 region of the hippocampus were trained in one-trial step-down inhibitory avoidance, and submitted to four consecutive daily test sessions without the footshock. This produced extinction of the conditioned response in control animals. The bilateral infusion into the CA1 region of the dorsal hippocampus of two different inhibitors of gene transcription, DRB (80 microg/side) or alpha-amanitin (25 pg/side), or of the protein synthesis inhibitor, anisomycin (80 microg/side) blocked extinction of the CR. The treatments were effective when given 15 min before, but not 1 or 3h after the first test session. Retrieval itself was not affected by the drugs. The treatments did not affect general activity in an open field or anxiety levels measured in an elevated plus maze. The data indicate that gene transcription and protein synthesis are necessary at the time of the first test session in order to generate extinction. These requirements are to be expected from learning that involves new synaptic associations.
