Receptor and transporter binding and activity profiles of albiflorin extracted from Radix paeoniae Alba.

Albiflorin, a traditional Chinese herb, is a main component of Radix paeoniae Alba, which has been used for the treatment of depressive disorders since ancient times. However, the mechanism of the antidepressant effect of albiflorin is poorly understood. Thus, we explored the binding profile of albiflorin at neurotransmitter receptors and transporters. We also characterised the in vivo effect of albiflorin on monoaminergic systems by using microanalysis to determine the extracellular levels of serotonin (5-HT) and norepinephrine (NE) in the hypothalamus of freely moving rats administered albiflorin. We found that albiflorin inhibited the uptake of 5-HT and NE and displayed robust binding affinities for the transporters of both neurotransmitters. By contrast, albiflorin (10 µM) showed no significant affinity to a wide array of central nervous system receptors. The results of our in vivo microdialysis studies showed that administration of albiflorin (3.5, 7.0, 14.0 mg/kg) significantly increased extracellular concentrations of 5-HT and NE in the hypothalamus of freely moving rats. Overall, the current study showed that albiflorin is a novel 5-HT and NE reuptake inhibitor with high selectivity.

The antidepressant-like pharmacological profile of Yuanzhi-1, a novel serotonin, norepinephrine and dopamine reuptake inhibitor.

Triple reuptake inhibitors that block dopamine transporters (DATs), norepinephrine transporters (NETs), and serotonin transporters (SERTs) are being developed as a new class of antidepressants that might have better efficacy and fewer side effects than traditional antidepressants. In this study, we performed in vitro binding and uptake assays as well as in vivo behavioural tests to assess the pharmacological properties and antidepressant-like efficacy of Yuanzhi-1. In vitro, Yuanzhi-1 had a high affinity for SERTs, NETs, and DATs prepared from rat brain tissue (Ki=3.95, 4.52 and 0.87nM, respectively) and recombinant cells (Ki=2.87, 6.86 and 1.03nM, respectively). Moreover, Yuanzhi-1 potently inhibited the uptake of serotonin (5-hydroxytryptamine; 5-HT), norepinephrine (NE) and dopamine (DA) into rat brain synaptosomes (Ki=2.12, 4.85 and 1.08nM, respectively) and recombinant cells (Ki=1.65, 5.32 and 0.68nM, respectively). In vivo, Yuanzhi-1 decreased immobility in a dose-dependent manner, which was shown among rats via the forced-swim test (FST) and mice via the tail-suspension test (TST). The results observed in the behavioural tests did not appear to result from the stimulation of locomotor activity. Repeated Yuanzhi-1 treatment (2.5, 5 or 10mg/kg) significantly reversed depression-like behaviours in chronically stressed rats, including reduced sucrose preference, decreased locomotor activity, and prolonged time to begin eating. Furthermore, in vivo microdialysis studies showed that 5- and 10-mg/kg administrations of Yuanzhi-1 significantly increased the extracellular concentrations of 5-HT, NE and DA in the frontal cortices of freely moving rats. Therefore, Yuanzhi-1 might represent a novel triple reuptake inhibitor and possess antidepressant-like activity.

The discovery of Yuanzhi-1, a triterpenoid saponin derived from the traditional Chinese medicine, has antidepressant-like activity.

Yuanzhi, the dried root of Polygala tenuifolia Willd., is a well-known traditional Chinese medicine used for its sedative, antipsychotic, cognitive improving, neuroprotective, and antidepressant effects. The present study was designed to screen and identify the antidepressant-like effect of six triterpenoid saponin components derived from Yuanzhi (Yuanzhi-1 to Yuanzhi-6) using in vitro radioligand receptor binding assays and in vivo behavioral tests. Yuanzhi-1, -3, -5 and -6 were shown to have antidepressant-like activity in the tail suspension test and forced swim test in mice, with no stimulant effect on locomotor activity. The minimal effective dose of Yuanzhi-1 (2.5 mg/kg) was lower than that of duloxetine (5mg/kg), a serotonin and norepinephrine reuptake inhibitor commonly used in the treatment of depression. Yuanzhi-1 (1 nM) had a high affinity for serotonin, norepinephrine and dopamine transporters. Acute toxicity tests indicated that the LD50 of Yuanzhi-1 (86.5mg/kg) was similar to that of duloxetine (73.2 mg/kg). These findings demonstrate that Yuanzhi-1 has a potential to be a novel triple monoamine reuptake inhibitor of antidepressant-like activity.

The discovery of 071031B, a novel serotonin and noradrenaline reuptake inhibitor.

Depression is a severe mood disorder with increasing morbidity and suicidality, while the current therapy is not satisfactory. Serotonin and noradrenaline reuptake inhibitors (SNRIs) have been reported to have higher efficacy and/or faster acting rate than commonly used antidepressants. The present study was designed to screen the potential SNRIs, using in vitro radioligand receptor binding assays and in vivo animal tests, and introduced the discovery of 071031B. In the tail suspension test and forced swimming test in mice, six compounds (071017S, 071026W, 071031A, 071031B, 080307A and 080307B) showed robust antidepressant activity, without stimulant effect on the locomotor activity or other side effects, and the minimal effective dose of 071017S, 071026W, 071031A and 071031B was less than that of duloxetine; in vitro binding tests indicated that 071031B had high affinity to both serotonin transporter and noradrenaline transporter with similar inhibitory rates to duloxetine at 1 and 100 nM; acute toxicity test indicated that the LD50 value of 071031B was similar to that of duloxetine. These findings demonstrated that this integrated system, combining high throughput screening technology and in vivo animal tests, is effective to screen potential monoamine reuptake inhibitors fast and accurately; 071031B is expected to be a novel serotonin and noradrenaline reuptake inhibitor for its robust antidepressant activity and transporter affinity.

The extracts of Fructus Akebiae, a preparation containing 90% of the active ingredient hederagenin: serotonin, norepinephrine and dopamine reuptake inhibitor.

Fructus Akebiae is a traditional Chinese herbal extract that has been used for the treatment of depressive disorders in China. Previous studies demonstrated that Fructus Akebiae extracts (FAE) displayed a potent antidepressant-like activity in animal behavior tests and found that the specific active ingredient from the extracts of Fructus Akebiae is hederagenin. However, the underlying mechanism is unknown. Here we provide evidences that FAE enhances the signaling of central monoamines via inhibition of the reuptake of the extracellular monoamines including serotonin (5-HT), norepinephrine (NE) and dopamine (DA). In rat brain membrane preparations and HEK293 cells transfected with human serotonin transporter (SERT), NE transporter (NET) and DA transporter (DAT), we found that FAE displayed marked affinity to rat and cloned human monoamine transporters in ex vivo and in vitro experiments, using competitive radio ligand binding assay. In uptake assays using rat synaptosomes and transfected cells, FAE was found to significantly inhibit all three monoamine transporters in a dose- and time-dependent manner, with a comparable or better potency to their corresponding specific inhibitors. In contrast, FAE (10 µM), showed no significant affinity to a variety array of receptors tested from CNS. In support of our uptake data, in vivo microdialysis studies showed that administration of FAE (12.6, 25, 50 mg/kg) significantly increased extracellular concentrations of 5-HT, NE and DA in frontal cortex of freely moving rats. Taken together, our current study showed for the first time that FAE is a novel triple inhibitor of monoamine transporters, which may be one the mechanisms of its antidepressant activity.