Effect of the NMDA receptor partial agonist, d-cycloserine, on emotional processing and autobiographical memory

Can ketamine and other glutamate receptor modulators be considered entactogens?

Subanesthetic-dose ketamine has recently been reported to improve hedonic pleasures associated with social interactions and altruism in individuals with treatment-resistant depression. However, whether ketamine-among other glutamate receptor modulators-also improves empathy and/or prosocial behavior in humans remains unknown. Under a framework grounded in neurobiology that proposes that prosocial behavior is preceded by empathy, this systematic review sought to: (1) explore the entactogenic effects of glutamate receptor modulators observed in clinical trials (as either primary or secondary outcomes), and (2) synthesize the findings regarding which glutamate receptor modulators produce entactogenic effects. Thirty studies that included self-reported ratings, neuroimaging, and/or behavioral task outcomes met inclusion criteria suggesting potential entactogenic effects associated with ketamine and, to less convincing extent, d-cycloserine (DCS). The findings suggest that ketamine and DCS may modulate self- and other-perception, involving changes in activity in brain regions involved in empathetic concerns and mentalizing, the ability to understand one's own and others' thoughts and feelings. These findings may guide potential therapeutic interventions for neuropsychiatric conditions associated with impaired empathy and prosocial behavior, including mood disorders, neurodevelopmental disorders, psychotic disorders, and personality disorders.

Effect of single intravenous injection of esketamine on postpartum depression after labor analgesia and potential mechanisms: a randomized, double-blinded controlled trial

BACKGROUND

The study was designed to investigate effects of single intravenous injection of esketamine on the incidence of postpartum depression (PPD) after labor analgesia and explore the potential mechanisms.

METHODS

A total of 120 women who underwent labor analgesia by epidural analgesia pump were enrolled and divided into two groups randomly. Esketamine at a dose of 0.2 mg/kg was intravenously injected after fetal disengagement in the test group and placebo was administered in the control group. The occurrence of PPD and side effects after delivery were recorded. Some indicators related to stress and inflammation were measured before labor analgesia and at 24 h, 1 week, and 6 weeks after delivery in this study. Data were analyzed by independent t-test, repeated measures analysis of variance and Chi-square test in SPSS software (version 25.0). It was considered statistically significant since a p value less than 0.05.

RESULTS

The incidence of PPD was significantly decreased both for one week and six weeks after delivery by using of esketamine (3.4% vs. 15.3%, p = 0.004 and 5.2% vs. 18.6%, p = 0.006, respectively). There were also significant differences between the stress and inflammation-related indicators in different time points in this study, while the side effects for 48 h after delivery were similar between the two groups.

CONCLUSIONS

Single intravenous injection of esketamine after delivery in participants underwent labor analgesia can decrease the occurrence of postpartum depression for one week and six weeks after delivery, while the side effects were not increased. The antidepressant effects of esketamine may be related to the reduction of stress response and inflammation.

TRIAL REGISTRATION

The trial was registered at the Chinese Clinical Trial Registry on 5/30/2022 (CTRI registration number-ChiCTR2200060387). URL of registry: https://www.chictr.org.cn/bin/home .

A systematic review of the pharmacological modulation of autobiographical memory specificity

Background

Over-general autobiographical memory (AM) retrieval is proposed to have a causal role in the maintenance of psychological disorders like depression and PTSD. As such, the identification of drugs that modulate AM specificity may open up new avenues of research on pharmacological modeling and treatment of psychological disorders.

Aim

The current review summarizes randomized, placebo-controlled studies of acute pharmacological modulation of AM specificity.

Method

A systematic search was conducted of studies that examined the acute effects of pharmacological interventions on AM specificity in human volunteers (healthy and clinical participants) measured using the Autobiographical Memory Test.

Results

Seventeen studies were identified (986 total participants), of which 16 were judged to have low risk of bias. The presence and direction of effects varied across drugs and diagnostic status of participants (clinical vs. healthy volunteers). The most commonly studied drug-hydrocortisone-produced an overall impairment in AM specificity in healthy volunteers [g = -0.28, CI (-0.53, -0.03), p = 0.03], although improvements were reported in two studies of clinical participants. In general, studies of monoamine modulators reported no effect on specificity.

Conclusion

Pharmacological enhancement of AM specificity is inconsistent, although monaminergic modulators show little promise in this regard. Drugs that reduce AM specificity in healthy volunteers may be useful experimental-pharmacological tools that mimic an important transdiagnostic impairment in psychological disorders.

Systematic review registration

PROSPERO, identifier CRD42020199076, https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020199076.

Selective attention to emotional stimuli and emotion recognition in patients with major depression: The role of mineralocorticoid and glutamatergic NMDA receptors

BACKGROUND

Mineralocorticoid receptors (MR) are highly expressed in limbic brain areas and prefrontal cortex, which are closely related to selective attention to emotional stimuli and emotion recognition. Patients with major depressive disorder (MDD) show alterations in MR functioning and both cognitive processes. MR stimulation improves cognitive processes in MDD and leads to glutamate release that binds upon N-methyl-D-aspartate receptors (NMDA-R).

AIMS

We examined (1) whether MR stimulation has beneficial effects on selective attention to emotional stimuli and on emotion recognition and (2) whether these advantageous effects can be improved by simultaneous NMDA-R stimulation.

METHODS

We examined 116 MDD patients and 116 healthy controls matched for age (M = 34 years), sex (78% women), and education in the following conditions: no pharmacological stimulation (placebo), MR stimulation (0.4 mg fludrocortisone + placebo), NMDA-R stimulation (placebo + 250 mg D-cycloserine (DCS)), MR + NMDA-R stimulation (fludrocortisone + DCS). An emotional dot probe task and a facial emotion recognition task were used to measure selective attention to emotional stimuli and emotion recognition.

RESULTS

Patients with MDD and healthy individuals did not differ in task performance. MR stimulation had no effect on both cognitive processes in both groups. Across groups, NMDA-R stimulation had no effect on selective attention but showed a small effect on emotion recognition by increasing accuracy to recognize angry faces.

CONCLUSIONS

Relatively young unmedicated MDD patients showed no depression-related cognitive deficits compared with healthy controls. Separate MR and simultaneous MR and NMDA-R stimulation revealed no advantageous effects on cognition, but NMDA-R might be involved in emotion recognition.