Increased sensitivity to psychomotor effects of ketamine enantiomers in the Wistar-Kyoto depression model.
Study Goal
The researchers aimed to compare the behavioral effects of R- and S-ketamine in a clinically relevant treatment protocol, focusing on both therapeutic and undesirable psychomotor effects in a depression model and control animals.
Results Summary
S-ketamine showed stronger acute psychomotor effects than R-ketamine, with Wistar-Kyoto rats (depression model) being more sensitive to these effects. Repeated treatment led to sensitization to locomotor stimulation and tolerance to ataxic effects, but no persistent changes were observed.
Population
Wistar-Kyoto rats (depression model) and Wistar rats (control).
Effective Dosage
10 mg/kg
Duration
Not explicitly stated (repeated treatment protocol).
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
S-ketamine | increase | acute psychomotor effects | Wistar-Kyoto rats and Wistar rats | - | has stronger acute psychomotor effects | #1 |
S-ketamine | increase | locomotor stimulating effects | Wistar-Kyoto rats and Wistar rats | - | sensitization to locomotor stimulating effects develops | #2 |
S-ketamine | decrease | ataxic effects | Wistar-Kyoto rats and Wistar rats | - | tolerance to ataxic effects develops | #3 |
ketamine treatments | no change | working memory, anxiety, and behavioral despair | Wistar-Kyoto rats and Wistar rats | - | found no persistent changes | #4 |
ketamine | increase | negative side effects | depressed patients | - | depressed patients would be more prone to negative side effects | #5 |
ketamine | decrease | side effects | depressed patients | - | tolerance to side effects may develop | #6 |
Ketamine, a fast-acting antidepressant, is a racemic mixture, composed of equal amounts of R- and S-ketamine. Preclinical studies are comparing them to better understand their role in therapeutic and undesirable effects. An important research gap is that studies do not use long clinically relevant protocols to compare the desired and undesired effects of ketamine enantiomers in modeled and control animals. In our preclinical study, we explored the behavioral effects of R- and S-ketamine at 10 mg/kg in clinically relevant treatment protocol using Wistar-Kyoto rats as a depression model and Wistar rats as a control. Undesirable psychomotor effects were evaluated with locomotor stimulation and sensitization, ataxia, and stereotypy. Persistent effects associated with therapeutic outcomes were evaluated by measuring working memory, anxiety, and behavioral despair. We found that S-ketamine has stronger acute psychomotor effects compared to R-ketamine and that Wistar-Kyoto rats are more sensitive to these effects compared to Wistar rats. After repeated treatment, sensitization to locomotor stimulating effects, and tolerance to ataxic effects of S-ketamine develops. We found no persistent changes due to ketamine treatments. Taken together, our results may indicate that depressed patients would be more prone to negative side effects of ketamine, compared to healthy controls. However, after repeated treatment, tolerance to side effects may develop and make the treatment more tolerable. Future preclinical and clinical studies are needed to address neurobiological mechanisms and clinical relevance of higher sensitivity to the psychomotor effects of ketamine, and the development of tolerance to psychomotor effects of ketamine in depressed individuals.