Behavioral Effects of 4-CMC and 4-MeO-PVP in DBA/2J Mice After Acute and Intermittent Administration and Following Withdrawal from Intermittent 14-Day Treatment

Neurochemical and Cardiovascular Effects of 4-Chloro Ring-Substituted Synthetic Cathinones in Rats

Synthetic cathinones are a class of new psychoactive substances that display psychomotor stimulant properties, and novel cathinone analogs continue to emerge in illicit drug markets worldwide. The aim of the present study was to characterize the pharmacology of 4-chloro ring-substituted cathinones that are appearing in illicit drug markets compared with the effects of 4-methylmethcathinone (mephedrone). Synaptosomes were prepared from rat caudate for dopamine transporter (DAT) assays or from whole brain minus caudate and cerebellum for norepinephrine transporter (NET) and serotonin transporter (SERT) assays. Findings from transporter uptake inhibition and release assays showed that mephedrone and 4-chloromethcathinone (4-CMC) function as substrates at DAT, NET, and SERT, with similar potency at all three transporters. In contrast, 4-chloro-α-pyrrolidinopropiophenone (4-CαPPP) was an uptake inhibitor at DAT and NET, with similar potency at each site, but had little activity at SERT. 4-Chloroethcathinone (4-CEC) was a low-potency uptake inhibitor at DAT and NET but a substrate at SERT. In rats implanted with telemetry transmitters, mephedrone and 4-CMC increased blood pressure, heart rate, and locomotor activity to a similar extent. 4-CEC and 4-CαPPP were less potent at increasing blood pressure and had modest stimulatory effects on heart rate and activity. 4-CMC also transiently decreased temperature at the highest dose tested. All three 4-chloro ring-substituted cathinones are biologically active, but only 4-CMC has potency comparable to mephedrone. Collectively, our findings suggest that 4-CMC and other 4-chloro cathinones may have abuse potential and adverse effects in humans that are analogous to those associated with mephedrone. SIGNIFICANCE STATEMENT: The 4-chloro ring-substituted cathinones all produced significant cardiovascular stimulation, with 4-chloromethcathinone (4-CMC) showing potency similar to mephedrone. All of the drugs are likely to be abused given their effects at the dopamine transporter, particularly 4-CMC.

Methcathinone Increases Visually-evoked Neuronal Activity and Enhances Sensory Processing Efficiency in Mice

Methcathinone (MCAT) belongs to the designer drugs called synthetic cathinones, which are abused worldwide for recreational purposes. It has strong stimulant effects, including enhanced euphoria, sensation, alertness, and empathy. However, little is known about how MCAT modulates neuronal activity in vivo. Here, we evaluated the effect of MCAT on neuronal activity with a series of functional approaches. C-Fos immunostaining showed that MCAT increased the number of activated neurons by 6-fold, especially in sensory and motor cortices, striatum, and midbrain motor nuclei. In vivo single-unit recording and two-photon Ca2+ imaging revealed that a large proportion of neurons increased spiking activity upon MCAT administration. Notably, MCAT induced a strong de-correlation of population activity and increased trial-to-trial reliability, specifically during a natural movie stimulus. It improved the information-processing efficiency by enhancing the single-neuron coding capacity, suggesting a cortical network mechanism of the enhanced perception produced by psychoactive stimulants.

Synthetic Cathinones and Neurotoxicity Risks: A Systematic Review

According to the EU Early Warning System (EWS), synthetic cathinones (SCs) are the second largest new psychoactive substances (NPS) class, with 162 synthetic cathinones monitored by the EU EWS. They have a similar structure to cathinone, principally found in Catha Edulis; they have a phenethylamine related structure but also exhibit amphetamine-like stimulant effects. Illegal laboratories regularly develop new substances and place them on the market. For this reason, during the last decade this class of substances has presented a great challenge for public health and forensic toxicologists. Acting on different systems and with various mechanisms of action, the spectrum of side effects caused by the intake of these drugs of abuse is very broad. To date, most studies have focused on the substances’ cardiac effects, and very few on their associated neurotoxicity. Specifically, synthetic cathinones appear to be involved in different neurological events, including increased alertness, mild agitation, severe psychosis, hyperthermia and death. A systematic literature search in PubMed and Scopus databases according to PRISMA guidelines was performed. A total of 515 studies published from 2005 to 2022 (350 articles from PubMed and 165 from Scopus) were initially screened for eligibility. The papers excluded, according to the criteria described in the Method Section (n = 401) and after full text analyses (n = 82), were 483 in total. The remaining 76 were included in the present review, as they met fully the inclusion criteria. The present work provides a comprehensive review on neurotoxic mechanisms of synthetic cathinones highlighting intoxication cases and fatalities in humans, as well as the toxic effects on animals (in particular rats, mice and zebrafish larvae). The reviewed studies showed brain-related adverse effects, including encephalopathy, coma and convulsions, and sympathomimetic and hallucinogenic toxidromes, together with the risk of developing excited/agitated delirium syndrome and serotonin syndrome.

Alpha-pyrrolidinopentiothiophenone (α-PVT) activates the TLR-NF-κB-MAPK signaling pathway and proinflammatory cytokine production and induces behavioral sensitization in mice

Synthetic cathinones are chemical derivatives of cathinone, a structural analog to amphetamine. It has been shown that synthetic cathinones have abuse potentials similar to psychomotor stimulants such as amphetamine and induce neuroinflammation. Among the novel synthetic cathinones, α-pyrrolidinopentiothiophenone (α-PVT) has been known to produce rewarding and reinforcing effects in rodent models. However, it has not yet been determined whether α-PVT induces neuroinflammation in vivo. In the present study, mice were exposed to repeated saline or α-PVT (20 mg/kg, intraperitoneally) for 7 days to test changes in locomotor activity and neuroinflammation-related factors in the striatum of mice. Repeated administration of α-PVT significantly induced locomotor sensitization. In addition, repeated α-PVT administration significantly increased the number of microglial cells, accompanied by marked increases in TLR1, TLR4, TLR6, and TLR7 mRNA levels in the striatum of mice. Furthermore, acute or repeated α-PVT administration increased the levels of phosphorylated NF-κB, ERK, p38, and JNK MAPK activation and repeated α-PVT, but not acute, increased the levels of TNF-α and IL-6 mRNA in the striatum of mice. Finally, systemic administration of TAK-242 (5 mg/kg, i.p.) or MPLA (50 μg/kg, i.p.), each an inhibitor or activator of TLR4, did not change α-PVT-induced behavioral sensitization in mice. These results suggest that the activation of TLR4 by repeated α-PVT administration may lead to neuroinflammation via TLR-mediated NF-κB and MAPK signaling pathways and the production of TNF-α and IL-6 in the striatum of mice, at least without the regulation of behavioral sensitization.