Somatodendritic 5-hydroxytryptamine1A (5-HT1A) autoreceptor function in major depression as assessed using the shift in electroencephalographic frequency spectrum with buspirone

Efficacy of Buspirone Augmentation of Escitalopram in Patients with Major Depressive Disorder with and without Atypical Features: A Randomized, 8 Week, Multicenter, Open-Label Clinical Trial

OBJECTIVE

This study investigated the treatment response and cognitive enhancement effects of buspirone augmentation of escitalopram in patients with major depressive disorder (MDD), according to atypical feature subtypes of MDD.

METHODS

An 8 week, randomized, parallel-controlled, open-label study was conducted. The Columbia Atypical Depression Diagnostic Scale was administered to evaluate atypical features. Patients were assigned randomly to the buspirone augmentation or non-buspirone groups. Symptom severity and cognitive function were evaluated using the 17-item Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale, Beck Depression Inventory, Beck Anxiety Inventory, digit span test, word fluency test, and Trail Making Tests A and B.

RESULTS

A total of 89 patients were recruited. There were no significant differences in the measures between the groups; however, among the MDD patients without atypical features, the digit span and word fluency tests were improved by treatment. In the MDD patients without atypical features, the buspirone augmentation group showed a significant improvement on the digit span test compared to the non-buspirone group.

CONCLUSION

Buspirone augmentation did not demonstrate significant benefits in MDD patients; however, buspirone augmentation showed greater efficacy for the improvement of cognitive function in MDD patients without atypical features. Our study suggests that atypical features are an important factor for cognitive enhancement in buspirone augmentation treatment in patients with MDD.

Overcoming Resistance to Selective Serotonin Reuptake Inhibitors: Targeting Serotonin, Serotonin-1A Receptors and Adult Neuroplasticity

Major depressive disorder (MDD) is the most prevalent mental illness contributing to global disease burden. Selective serotonin (5-HT) reuptake inhibitors (SSRIs) are the first-line treatment for MDD, but are only fully effective in 30% of patients and require weeks before improvement may be seen. About 30% of SSRI-resistant patients may respond to augmentation or switching to another antidepressant, often selected by trial and error. Hence a better understanding of the causes of SSRI resistance is needed to provide models for optimizing treatment. Since SSRIs enhance 5-HT, in this review we discuss new findings on the circuitry, development and function of the 5-HT system in modulating behavior, and on how 5-HT neuronal activity is regulated. We focus on the 5-HT1A autoreceptor, which controls 5-HT activity, and the 5-HT1A heteroreceptor that mediates 5-HT actions. A series of mice models now implicate increased levels of 5-HT1A autoreceptors in SSRI resistance, and the requirement of hippocampal 5-HT1A heteroreceptor for neurogenic and behavioral response to SSRIs. We also present clinical data that show promise for identifying biomarkers of 5-HT activity, 5-HT1A regulation and regional changes in brain activity in MDD patients that may provide biomarkers for tailored interventions to overcome or bypass resistance to SSRI treatment. We identify a series of potential strategies including inhibiting 5-HT auto-inhibition, stimulating 5-HT1A heteroreceptors, other monoamine systems, or cortical stimulation to overcome SSRI resistance.

Increased functional coupling of 5-HT1A autoreceptors to GIRK channels in Tph2-/- mice

Firing activity of serotonergic neurons is under regulatory control by somatodendritic 5-HT_1A autoreceptors (5-HT_1AARs). Enhanced 5-HT_1AAR functioning may cause decreased serotonergic signaling in brain and has thereby been implicated in the etiology of mood and anxiety disorders. Tryptophan hydroxylase-2 knockout (Tph2^-/-) mice exhibit sensitization of 5-HT_1A agonist-induced inhibition of serotonergic neuron firing and thus represents a unique animal model of enhanced 5-HT_1AAR functioning. To elucidate the mechanisms underlying 5-HT_1AAR supersensitivity in Tph2^-/- mice, we characterized the activation of G protein-coupled inwardly-rectifying potassium (GIRK) conductance by the 5-HT_1A receptor agonist 5-carboxamidotryptamine using whole-cell recordings from serotonergic neurons in dorsal raphe nucleus. Tph2^-/- mice exhibited a mean twofold leftward shift of the agonist concentration-response curve (p < 0.001) whereas the maximal response, proportional to the 5-HT_1AAR number, was not different (p = 0.42) compared to Tph2^+/- and Tph2^+/+ littermates. No differences were found in the basal inwardly-rectifying potassium conductance, determined in the absence of agonist, (p = 0.80) nor in total GIRK conductance activated by intracellular application of GTP-γ-S (p = 0.69). These findings indicate increased functional coupling of 5-HT_1AARs to GIRK channels in Tph2^-/- mice without a concomitant increase in 5-HT_1AARs and/or GIRK channel density. In addition, no changes were found in α₁-adrenergic facilitation of firing (p = 0.72) indicating lack of adaptive changes Tph2^-/- mice. 5-HT_1AAR supersensitivity may represents a previously unrecognized cause of serotonergic system hypofunction and associated disorders and provides a possible explanation for conflicting results on the correlation between 5-HT_1AAR density and depression in clinical imaging studies.

Modified Suanzaorentang Had the Treatment Effect for Generalized Anxiety Disorder for the First 4 Weeks of Paroxetine Medication: A Pragmatic Randomized Controlled Study

Background. Paroxetine does not show satisfactory therapeutic effect for generalized anxiety disorder (GAD) patients for the first 2–4 weeks of medication. Diazepam is always concurrently used although it has some shortcomings such as physical dependence and withdrawal reactions. In this study, we aimed to identify whether modified Suanzaorentang (MSZRT), a combined Chinese formula including Suanzaorentang (SZRT) and Zhizichitang (ZZCT), could control the anxiety of GAD for the first 4 weeks of paroxetine medication. Methods. 156 GAD patients were randomized to the treatment of paroxetine, paroxetine-diazepam, or paroxetine-MSZRT for 4 weeks. Hamilton Anxiety Scale (HAMA) Test and Self-Rating Anxiety Scale (SAS) Test were determined each week as the evaluation of clinical efficacy. Adverse events (AEs) were also closely observed by performing the Treatment Emergent Symptom Scale (TESS) Test. Results. Both paroxetine-MSZRT and paroxetine-diazepam decreased more HAMA and SAS total scores than paroxetine from weeks 1 to 3. Paroxetine-MSZRT as well as paroxetine-diazepam had an obviously higher onset rate than paroxetine in each week. After 4 weeks' treatment, the overall effectiveness rate in the paroxetine-MSZRT group (90.00%) was obviously higher than those of the paroxetine group (74.42%) but did not significantly differ from the paroxetine-diazepam group (93.88%). Conclusion. MSZRT had the treatment effect for GAD when paroxetine was used for the first 4 weeks.