Prunella vulgaris Attenuates Prepulse Inhibition Deficit and Attention Disruption induced by MK-801 in Mice

A botanical drug composed of three herbal materials attenuates the sensorimotor gating deficit and cognitive impairment induced by MK-801 in mice

Objectives

A botanical drug derived from the ethanolic extract composed of Clematis chinensis Osbeck (Ranunculaceae), Trichosanthes kirilowii Maximowicz (Cucurbitaceae) and Prunella vulgaris Linné (Lamiaceae) has been used to ameliorate rheumatoid arthritis as an ethical drug in Korea. In our study, we investigated the effect of this herbal complex extract (HCE) on schizophrenia-like behaviours induced by MK-801.

Methods

HCE (30, 100 or 300 mg/kg, p.o) was orally administered to male ICR mice to a schizophrenia-like animal model induced by MK-801. We conducted an acoustic startle response task, an open-field task, a novel object recognition task and a social novelty preference task.

Key findings

We found that a single administration of HCE (100 or 300 mg/kg) ameliorated MK-801-induced abnormal behaviours including sensorimotor gating deficits and social or object recognition memory deficits. In addition, MK-801-induced increases in phosphorylated Akt and GSK-3β expression levels in the prefrontal cortex were reversed by HCE (30, 100 or 300 mg/kg).

Conclusions

These results imply that HCE ameliorates MK-801-induced dysfunctions in prepulse inhibition, social interactions and cognitive function, partly by regulating the Akt and GSK-3β signalling pathways.

Risperidone ameliorates cognitive deficits, promotes hippocampal proliferation, and enhances Notch signaling in a murine model of schizophrenia

Antipsychotic agents have been reported to promote hippocampal neurogenesis and improve cognitive deficits; yet, the molecular mechanisms underlying these actions remain unclear. In the present study, we used a murine model of schizophrenia induced by 5-day intraperitoneal injection with the non-competitive N-methyl-d-aspartate receptor antagonist MK801 (0.3mg/kg/day) to assess cognitive behavioral deficits, changes in Notch signaling, and cellular proliferation in the hippocampus of adult male C57BL/6 mice after 2-week administration of risperidone (Rip, 0.2mg/kg/day) or vehicle. We then utilized in vivo stereotaxic injections of a lentivirus expressing a short hairpin RNA (shRNA) for Notch1 into the dentate gyrus to examine the role of Notch1 in the observed actions of Rip. We found that Rip ameliorated cognitive deficits and restored cell proliferation in MK801-treated mice in a manner associated with the up-regulation of Notch signaling molecules, including Notch1, Hes1, and Hes5. Moreover, these effects were abolished by pretreatment with Notch1 shRNA. Our results suggest that the ability of Rip to improve cognitive function in schizophrenia is mediated in part by Notch signaling.

Oleanolic acid ameliorates cognitive dysfunction caused by cholinergic blockade via TrkB-dependent BDNF signaling

Oleanolic acid is a naturally occurring triterpenoid and is widely present in food and medicinal plants. To examine the effect of oleanolic acid on memory deficits, we employed a cholinergic blockade-induced cognitive deficit mouse model. A single administration of oleanolic acid significantly increased the latency on the passive avoidance task and affected the alternation behavior on the Y-maze task and the exploration time on the novel object recognition task, indicating that oleanolic acid reverses the cognitive impairment induced by scopolamine. In accordance with previous reports, oleanolic acid enhanced extracellular-signal-regulated kinase 1/2 (ERK1/2) and cAMP response element-binding protein (CREB) phosphorylation and brain-derived neurotrophic factor (BDNF) expression in the hippocampus. Interestingly, ameliorating effect of oleanolic acid on scopolamine-induced memory impairment was abolished by N2-(2-{[(2-oxoazepan-3-yl)amino]carbonyl}phenyl)benzo[b]thiophene-2-carboxamide (ANA-12), a potent and specific inhibitor of tropomyosin receptor kinase B (TrkB), in the passive avoidance task. Similarly, oleanolic acid significantly evoked long-term potentiation in a dose-dependent manner, which was diminished by ANA-12 treatment as shown in the electrophysiology study. Together, these results imply that oleanolic acid ameliorates scopolamine-induced memory impairment by modulating the BDNF-ERK1/2-CREB pathway through TrkB activation in mice, suggesting that oleanolic acid would be a potential therapeutic agent for the treatment of cognitive deficits.

Ursolic acid enhances pentobarbital-induced sleeping behaviors via GABAergic neurotransmission in mice

Prunella vulgaris is widely used as a herbal medicine for cancers, inflammatory diseases, and other infections. Although it has long been used, few studies have examined its effects on central nervous system function. Here, we first observed that ethanolic extracts of P. vulgaris (EEPV) prolonged pentobarbital-induced sleep duration in mice. It is known that EEPV consists of many active components including triterpenoid (ursolic acid and oleanolic acid), which have many biological activities. Therefore, we evaluated which EEPV components induced sleep extension in pentobarbital-mediated sleeping model in mice. Surprisingly, despite their structural similarity and other common functions such as anti-inflammation, anti-cancer, and tissue protection, only ursolic acid enhanced sleep duration in pentobarbital-treated mice. These results were attenuated by bicuculline treatment, which is a GABAA receptor antagonist. The present results suggest that ursolic acid from P. vulgaris enhances sleep duration through GABAA receptor activation and could be a therapeutic candidate for insomnia treatment.