L-DOPA improves extinction memory retrieval after successful fear extinction.
- 2019-06-26
- Psychopharmacology 236(12)
- A M V Gerlicher
- O Tüscher
- R Kalisch
- PubMed: 31243481
- DOI: 10.1007/s00213-019-05301-4
Study Design
- Type
- Randomized Controlled Trial (RCT)
- Sample size
- n = 79
- Population
- healthy male adults (experiment 1: 79, experiment 2: 32)
- Methods
- double-blind, randomized and placebo-controlled experiments comprising fear conditioning (day 1), extinction followed by administration of 150 mg L-DOPA or placebo (day 2), and a memory test (day 3)
- Blinding
- Double-blind
- Duration
- 3 days
- Funding
- Unclear
Rationale
A promising strategy to prevent a return of fear after exposure-based therapy in anxiety disorders is to pharmacologically enhance the extinction memory consolidation presumed to occur after exposure. Accumulating evidence suggests that the effect of a number of pharmacological consolidation enhancers depends on a successful fear reduction during exposure. Here, we employed the dopamine precursor L-DOPA to clarify whether its documented potential to enhance extinction memory consolidation is dependent on successful fear extinction.Methods
In two double-blind, randomized and placebo-controlled experiments (experiment 1: N = 79, experiment 2: N = 32) comprising fear conditioning (day 1), extinction followed by administration of 150 mg L-DOPA or placebo (day 2) and a memory test (day 3) in healthy male adults, conditioned responses were assessed as differential skin conductance responses. We tested whether the effect of L-DOPA on conditioned responses at test depended on conditioned responses at the end of extinction in an experiment with a short (10 trials, experiment 1) and long (25 trials, experiment 2) extinction session.Results
In both experiments, the effect of L-DOPA was dependent on conditioned responses at the end of extinction. That is, post-extinction L-DOPA compared to placebo administration reduced conditioned responses at test only in participants showing a complete reduction of conditioned fear at the end of extinction.Conclusion
The results support the potential use of L-DOPA as a pharmacological adjunct to exposure treatment, but point towards a common boundary condition for pharmacological consolidation enhancers: a successful reduction of fear in the exposure session.Research Insights
post-extinction L-DOPA compared to placebo administration reduced conditioned responses at test only in participants showing a complete reduction of conditioned fear at the end of extinction.
- Effect
- Beneficial
- Effect size
- Small
- Dose
- 150 mg