The psychomotor, reinforcing, and discriminative stimulus effects of synthetic cathinone mexedrone in male mice and rats

The chronic use of the novel synthetic cathinone mexedrone, like other psychoactive drugs, can be considered addictive, with a high potential for abuse and the ability to cause psychological dependence in certain users. However, little is known about the neurobehavioral effects of mexedrone in association with its potential for abuse. We investigated the abuse potential for mexedrone abuse through multiple behavioral tests. In addition, serotonin transporter (SERT) levels were measured in the synaptosome of the dorsal striatum, and serotonin (5-HT) levels were measured in the dorsal striatum of acute mexedreone (50 mg/kg)-treated mice. To clarify the neuropharmacological mechanisms underlying the locomotor response of mexedrone, the 5-HT2A receptor antagonist M100907 (0.5 or 1.0 mg/kg) was administered prior to the acute injection of mexedrone in the locomotor activity experiment in mice. Mexedrone (10-50 mg/kg) produced a significant place preference in mice and mexedrone (0.1-0.5 mg/kg/infusion) maintained self-administration behavior in rats in a dose-dependent manner. In the drug discrimination experiment, mexedrone (5.6-32 mg/kg) was fully substituted for the discriminative stimulus effects of cocaine in rats. Mexedrone increased locomotor activity, and these effects were reversed by pretreatment with M100907. Acute mexedrone significantly increased c-Fos expression in the dorsal striatum and decreased SERT levels in the synaptosome of the dorsal striatum of mice, resulting in an elevation of 5-HT levels. Taken together, our results provide the possibility that mexedrone has abuse potential, which might be mediated, at least in part, by the activation of the serotonergic system in the dorsal striatum.

Asparagus cochinchinensis extract ameliorates menopausal depression in ovariectomized rats under chronic unpredictable mild stress

BACKGROUND

Depression is a serious and common psychiatric disorder generally affecting more women than men. A woman's risk of developing depression increases steadily with age, and higher incidence is associated with the onset of menopause. Here we evaluated the antidepressant properties of Asparagus cochinchinensis (AC) extract and investigated its underlying mechanisms in a rat menopausal depression model.

METHODS

To model this menopausal depression, we induced a menopause-like state in rats via ovariectomy and exposed them to chronic unpredictable mild stress (CUMS) for 6 weeks, which promotes the development of depression-like symptoms. During the final 4 weeks of CUMS, rats were treated with either AC extract (1000 or 2000 mg/kg, PO), which has been reported to provide antidepressant effects, or with the tricyclic antidepressant imipramine (10 mg/kg, IP).

RESULTS

We report that CUMS promotes depression-like behavior and significantly increases serum corticosterone and inflammatory cytokine levels in the serum of ovariectomized (OVX) rats. We also found that CUMS decreases the expression of brain-derived neurotrophic factor (BDNF) and its primary receptor, tropomyosin receptor kinase B (TrkB), in OVX rats, and treatment with AC extract rescues both BDNF and TrkB expression levels.

CONCLUSION

These results suggest that AC extract exerts antidepressant effects, possibly via modulation of the BDNF-TrkB pathway, in a rat model of menopausal depression.

The Abuse Potential of Novel Synthetic Phencyclidine Derivative 1-(1-(4-Fluorophenyl)Cyclohexyl)Piperidine (4'-F-PCP) in Rodents

The dissociative anesthetic phencyclidine (PCP) and PCP derivatives, including 4′-F-PCP, are illegally sold and abused worldwide for recreational and non-medical uses. The psychopharmacological properties and abuse potential of 4′-F-PCP have not been fully characterized. In this study, we evaluated the psychomotor, rewarding, and reinforcing properties of 4′-F-PCP using the open-field test, conditioned place preference (CPP), and self-administration paradigms in rodents. Using Western immunoblotting, we also investigated the expression of dopamine (DA)-related proteins and DA-receptor-mediated downstream signaling cascades in the nucleus accumbens (NAc) of 4′-F-PCP-self-administering rats. Intraperitoneal administration of 10 mg/kg 4′-F-PCP significantly increased locomotor and rearing activities and increased CPP in mice. Intravenous administration of 1.0 mg/kg/infusion of 4′-F-PCP significantly enhanced self-administration during a 2 h session under fixed ratio schedules, showed a higher breakpoint during a 6 h session under progressive ratio schedules of reinforcement, and significantly altered the expression of DA transporter and DA D1 receptor in the NAc of rats self-administering 1.0 mg/kg 4′-F-PCP. Additionally, the expression of phosphorylated (p) ERK, pCREB, c-Fos, and FosB/ΔFosB in the NAc was significantly enhanced by 1.0 mg/kg 4′-F-PCP self-administration. Taken together, these findings suggest that 4′-F-PCP has a high potential for abuse, given its robust psychomotor, rewarding, and reinforcing properties via activation of DAergic neurotransmission and the downstream signaling pathways in the NAc.