l-Stepholidine increases the frequency of sEPSC via the activation of D1 dopamine signaling pathway in rat prelimbic cortical neurons

Tetrahydroprotoberberines: A Novel Source of Pharmacotherapies for Substance Use Disorders?

Tetrahydroprotoberberines (THPBs) are a class of compounds that target both dopamine D1 and D2 families of receptors, making them attractive candidates for treating substance use disorder (SUD). The binding of some THPBs to serotonin and adrenergic receptors, in addition to dopamine receptors, gives rise to complex pharmacological profiles. Significant progress has been made over the last decade in examining these compounds for their therapeutic potential. Here, we evaluate recent discoveries relating to the neural mechanism and therapeutic effects of THPBs, focusing on compounds that have shown promise in animal models of SUD and preliminary clinical studies. Advancements in structure-activity relationship studies and in silico modeling of THPB binding to dopamine receptors have facilitated the synthesis of novel THPBs with enhanced therapeutic properties and provide insights regarding use of the THPB scaffold to serve as a template for innovative drug designs.

L-Stepholidine rescues memory deficit and synaptic plasticity in models of Alzheimer's disease via activating dopamine D1 receptor/PKA signaling pathway

It is accepted that amyloid β-derived diffusible ligands (ADDLs) have a prominent role in triggering the early cognitive deficits that constitute Alzheimer's disease (AD). However, there is still no effective treatment for preventing or reversing the progression of the disease. Targeting α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor trafficking and its regulation is a new strategy for AD early treatment. Here we investigate the effect and mechanism of L-Stepholidine (L-SPD), which elicits dopamine D1-type receptor agonistic activity, while acting as D2-type receptor antagonist on cognition and synaptic plasticity in amyloid precursor protein (APP) and presenilin 1 (PS1) double-transgenic (APP/PS1) mice, and hippocampal cultures or slices treated with ADDLs. L-SPD could improve the hippocampus-dependent memory, surface expression of glutamate receptor A (GluA1)-containing AMPA receptors and spine density in hippocampus of APP/PS1 transgenic mice. L-SPD not only rescued decreased phosphorylation and surface expression of GluA1 in hippocampal cultures but also protected the long-term potentiation in hippocampal slices induced by ADDLs. Protein kinase A (PKA) agonist Sp-cAMPS or D1-type receptor agonist SKF81297 had similar effects, whereas PKA antagonist Rp-cAMPS or D1-type receptor antagonist SCH23390 abolished the effect of L-SPD on GluA1 trafficking. This was mediated mainly by PKA, which could phosphorylate serine residue at 845 of the GluA1. L-SPD may be explored as a potential therapeutic drug for AD through a mechanism that improves AMPA receptor trafficking and synaptic plasticity via activating D1/PKA signaling pathway.

Design, synthesis and evaluation of benzo[a]thieno[3,2-g]quinolizines as novel l-SPD derivatives possessing dopamine D1, D2 and serotonin 5-HT1A multiple action profiles

A novel scaffold derived from l-SPD with a substituted thiophene group in the D ring were designed, synthesized, and evaluated for their binding affinities at dopamine (D1, D2 and D3) and serotonin (5-HT1A and 5-HT2A) receptors. Most of the tetracyclic compounds exhibited higher affinities for D2 and 5-HT1A receptors than l-SPD, while compound 23 e showed the highest Ki value of 7.54 nM at D2 receptor which was 14 times more potent than l-SPD. Additionally, compounds 23 d and 23 e were more potent than l-SPD at D3 receptor. According to the functional assays, 23 d and 23 e were demonstrated as full antagonists at D1 and D2 receptors and full agonists at 5-HT1A receptor. Since the combination of D2 antagonism and 5-HT1A agonism is considered effective in treating both the positive and negative symptoms of schizophrenia, these novel compounds are implicated as potential therapeutic agents.

A preclinical assessment of d.l-govadine as a potential antipsychotic and cognitive enhancer

Tetrahydroprotoberberines (THPBs) are compounds derived from traditional Chinese medicine and increasing preclinical evidence suggests efficacy in treatment of a wide range of symptoms observed in schizophrenia. A receptor-binding profile of the THPB, d.l-govadine (d.l-Gov), reveals high affinity for dopamine and noradrenaline receptors, efficacy as a D2 receptor antagonist, brain penetrance in the 10-300 ng/g range, and thus motivated an assessment of the antipsychotic and pro-cognitive properties of this compound in the rat. Increased dopamine efflux in the prefrontal cortex and nucleus accumbens, measured by microdialysis, is observed following subcutaneous injection of the drug. d.l-Gov inhibits both conditioned avoidance responding (CAR) and amphetamine-induced locomotion (AIL) at lower doses than clozapine (CAR ED50: d.l-Gov 0.72 vs. clozapine 7.70 mg/kg; AIL ED50: d.l-Gov 1.70 vs. clozapine 4.27 mg/kg). Catalepsy is not detectable at low biologically relevant doses, but is observed at higher doses. Consistent with previous reports, acute d-amphetamine disrupts latent inhibition (LI) while a novel finding of enhanced LI is observed in sensitized animals. Treatment with d.l-Gov prior to conditioned stimulus (CS) pre-exposure restores LI to levels observed in controls in both sensitized animals and those treated acutely with d-amphetamine. Finally, possible pro-cognitive properties of d.l-Gov are assessed with the spatial delayed win-shift task. Subcutaneous injection of 1.0 mg/kg d.l-Gov failed to affect errors at a 30-min delay, but decreased errors observed at a 12-h delay. Collectively, these data provide the first evidence that d.l-Gov may have antipsychotic properties in conjunction with pro-cognitive effects, lending further support to the hypothesis that THPBs are a class of compounds which merit serious consideration as novel treatments for schizophrenia.

Evaluation of the antipsychotic effect of bi-acetylated l-stepholidine (l-SPD-A), a novel dopamine and serotonin receptor dual ligand

Bi-acetylated l-stepholidine (l-SPD-A), a novel derivate of l-stepholidine (l-SPD), possesses a pharmacological profile of D(1)/5-HT(1A) agonism and D(2) antagonism. In the present study, we examined the potential antipsychotic effect of l-SPD-A in a phencyclidine (PCP)-induced rat model of schizophrenia. Pretreatment with l-SPD-A blocked acute PCP-induced hyperlocomotion and reversed prepulse inhibition (PPI) deficits. Chronic l-SPD-A administration (i.p., 10mg/kg/day for 14 days) improved social interaction and novel object recognition impairments in rats that were pretreated with PCP (i.p., 5mg/kg/day for 14 days). Moreover, in a conditioned avoidance response (CAR) test, l-SPD-A, with either i.p. or oral administration, significantly decreased active avoidance without affecting the escape response of rats. Importantly, compared to that of the parent compound l-SPD, l-SPD-A showed stronger suppression of CARs. Lastly, using a [(35)S]GTPgammaS binding assay, we demonstrated that l-SPD-A improved impaired dopamine D(1) receptor function in the prefrontal cortex (PFC) in chronic PCP-treated rats. Taken together, these results indicate that l-SPD-A was not only effective against the hyperactivity, but also improved the sensorimotor gating deficit, social withdrawal and cognitive impairment in an animal model of schizophrenia. The present data suggest that l-SPD-A, a potential neurotransmitter stabilizer, is a promising novel candidate drug for the treatment of schizophrenia.

Neuroactive steroid dehydroepiandrosterone sulfate inhibits 5-hydroxytryptamine (5-HT)-evoked glutamate release via activation of sigma-1 receptors and then inhibition of 5-HT3 receptors in rat prelimbic cortex

Dehydroepiandrosterone sulfate (DHEAS) is one of the most important neuroactive steroids. The present study examined the effect of DHEAS on spontaneous and evoked glutamate release in the pyramidal cells of layers V and VI of the rat prelimbic cortex by using whole-cell patch-clamp recordings in slices and further investigated its mechanism. The results showed that DHEAS at 1 microM had no effect on spontaneous glutamate release but inhibited 5-hydroxytryptaime (5-HT)-evoked glutamate release. The concentration-response relationship of this effect of DHEAS was U-shaped with a maximum at 1 microM, and this inhibition seemed to have some extent of selectivity for the 5-HT-evoked glutamate release because it had no effects on high K(+)-, electrical stimulus-, and dopamine-evoked releases. Further study showed that DHEAS inhibited the 5-HT(3) receptor agonist evoked-glutamate release but had no effect on the 5-HT(2A/2C) receptor agonist-evoked release. Moreover, the 5-HT(3) receptor antagonist could block the effect of DHEAS on the 5-HT-evoked glutamate release. The mechanism study showed that the sigma-1 receptor antagonist could block the effect of DHEAS and that the sigma-1 receptor agonist could mimic the effect of DHEAS on 5-HT(3) receptor agonist-evoked glutamate release and intrasynaptosomal Ca(2+) increase. These results suggest that DHEAS can inhibit 5-HT-evoked glutamate release via activation of the sigma-1 receptor and then inhibition of the 5-HT(3) receptor in the pyramidal cells of the prelimbic cortex.

Effects of (-)-stepholidine on NMDA receptors: comparison with haloperidol and clozapine

AIM

To examine whether (-)-stepholidine (SPD) has a direct effect on the N-methyl- D-aspartic acid receptors (NMDAR) containing the NMDA receptor subunits NR2A or NR2B and to compare its effect with those of haloperidol (Hal) and clozapine (Cloz).

METHODS

NMDAR was transiently expressed in human embryonic kidney 293 (HEK293) cells. Changes in intracellular calcium concentration ([Ca2+]i) induced by NMDAR activation were monitored with Fura-2 ratio imaging techniques.

RESULTS

SPD had no significant effects on either subunit of NMDAR at a concentration of less than 100 micromol/L. Hal selectively inhibited NMDAR containing the NR2B subunit, whereas Cloz inhibited both subunits of NMDAR. Although both Hal and Cloz inhibited NR1a/NR2B receptor-mediated Ca2+ influx, their effects were different. Hal was more potent and had a faster peak effect than Cloz.

CONCLUSION

Both Hal and Cloz inhibit NMDAR-mediated function, whereas SPD produced only a little inhibition at a high concentration. Based on our other studies, the modulation of SPD on NMDAR function may be via D1 receptor action underlying an indirect mechanism.