Δ9-Tetrahydrocannabinol-like discriminative stimulus effects of five novel synthetic cannabinoids in rats

A study on the possible neurotoxic effects of CUMYL-4CN-BINACA in Sprague Dawley rats

Substances such as Δ9-tetrahydrocannabinol (THC) and cannabidiol cross the blood-brain barrier. Detecting the damage of these substances in the brain provides important data in drug abuse studies. The aim of the study is to define the neurotoxicity of a novel synthetic cannabinoid (CUMYL-4CN-BINACA) in the Sprague-Dawley rats. Histopathological, immunohistochemical, behavioral, and biochemical examinations were performed to determine the acute and subacute toxicity of the cannabinoid. Three cannabinoid doses were administered for 2 days in the acute exposure groups and 14 days in the subacute exposure groups. Observations were made for 14 days and various changes such as mortality, injury, and illness were recorded daily. No mortality was determined. Serious pathological changes such as neurodegeneration, focal plague formation, vacuolation, edema, congestion, and fibrosis were observed in the cerebral cortex and hippocampus of the brain in a dose-dependent manner. Brain tissue caspase-3 activity showed that the cannabinoid triggered apoptosis in the rat brain. The detected cellular oxidative stress (higher lipid peroxidation and lower antioxidant enzyme activity) also supported neurotoxicity. Significant behavioral abnormalities were also observed in the acute groups, while no behavioral changes were detected in the subacute groups. This study showed for the first time that CUMYL-4CN-BINACA adversely affects the rat brain. It can be estimated that the abuse of the cannabinoid may harm human health in the same way.

Acute and subacute toxic effects of CUMYL-4CN-BINACA on male albino rats

PURPOSE

There is very little information about the toxicological and pathological effects of synthetic cannabinoids, which have cannabis-like properties. This study was carried out to histopathologically, hematologically, and biochemically determine the toxic effects of acute and subacute exposure to a novel synthetic cannabinoid 1-(4-cyanobutyl)-N-(2-phenylpropan-2-yl)indazole-3-carboxamide in internal organs of adult male rats.

METHODS

The cannabinoid was injected intraperitoneally at three doses (0.5, 1.0, and 2.0 mg/kg, body weight). The cannabinoid was administered to acute groups for 2 days and to subacute groups for 14 days. Observations were made for 14 days and various changes such as mortality, injury, and illness were recorded daily. Hematological and biochemical changes were evaluated and histopathological analyses in lung, liver, and kidney tissues were also performed.

RESULTS

No mortality was observed. It was observed that there were fluctuations in hematological and serum biochemical parameters. Among the oxidative stress parameters, significant decreases in superoxide dismutase, catalase levels and significant increases in lipid peroxidation levels were determined. Serious pathological changes such as necrosis, vacuolation, congestion, and fibrosis were observed in the internal organs in a dose-dependent and time-dependent manner. It was also found that the synthetic cannabinoid triggered apoptosis in the organs. The results demonstrated that the most affected organ by the cannabinoid was the kidney.

CONCLUSION

This study showed for the first time that CUMYL-4CN-BINACA adversely affects healthy male albino rats. It can be estimated that the abuse of the cannabinoid may harm human health in the same way.

Defining Steric Requirements at CB1 and CB2 Cannabinoid Receptors Using Synthetic Cannabinoid Receptor Agonists 5F-AB-PINACA, 5F-ADB-PINACA, PX-1, PX-2, NNL-1, and Their Analogues

Synthetic cannabinoid receptor agonists (SCRAs) are a diverse class of new psychoactive substances (NPS). They commonly comprise N-alkylated indole, indazole, or 7-azaindole scaffolds with amide-linked pendant amino acid groups. To explore the contribution of the amino acid side chain to the cannabinoid pharmacology of SCRA NPS, a systematic library of side chain-modified SCRAs was prepared based on the recent detections of amino acid derivatives 17 (5F-AB-PINACA), 18 (5F-ADB-PINACA), 15 (PX-1), 19 (PX-2), and 20 (NNL-1). In vitro binding affinities and functional activities at cannabinoid type 1 and 2 receptors (CB₁ and CB₂, respectively) were determined for all the library members using radioligand competition experiments and a fluorescence-based membrane potential assay. Binding affinities and functional activities varied widely across compounds (K_i = 0.32 to >10 000 nM, EC₅₀ = 0.24-1259 nM), with several clear structure-activity relationships (SARs) emerging. Affinity and potency at CB₁ changed as a function of the heterocyclic core (indazole > indole > 7-azaindole) and the pendant amino acid side chain (tert-butyl > iso-propyl > iso-butyl > benzyl > ethyl > methyl > hydrogen). Ensemble docking at CB₁ revealed a clear steric basis for observed SAR trends. Interestingly, although 15 (PX-1) and 19 (PX-2) have been detected in recreational drug markets, they failed to induce centrally CB₁-mediated effects (e.g., hypothermia) in mice using radiobiotelemetry. Together, these data provide insights regarding structural contributions to the cannabimimetic profiles of 17 (5F-AB-PINACA), 18 (5F-ADB-PINACA), 15 (PX-1), 19 (PX-2), 20 (NNL-1), and other SCRA NPS.

Behavioral pharmacology of five novel synthetic cannabinoids

Newly emerging synthetic cannabinoid compounds continue to be found in the designer drug market. They are often targeted as a 'legal high' alternative to traditional cannabinoids via 'darknet' markets and their increased potency and efficacy are becoming a growing concern internationally. The purpose of this study was to determine whether 4-CN-CUMYL-BUTINACA, 4F-MDMB-BINACA, 5F-AEB, 5F-CUMYL-P7AICA and EMB-FUBINACA exhibited similar behavioral effects as Δ9-tetrahydrocannabinol (Δ9-THC). Locomotor activity was assessed in an open-field assay using Swiss-Webster mice. Male Sprague-Dawley rats were trained to discriminate between intraperitoneal injections of Δ9-THC (3 mg/kg) and vehicle. Following successful training, substitution tests for 4-CN-CUMYL-BUTINACA, 4F-MDMB-BINACA, 5F-AEB, 5F-CUMYL-P7AICA and EMB-FUBINACA were conducted. All of the test compounds decreased locomotor activity. 4-CN-CUMYL-BUTINACA (ED50 = 0.26 mg/kg), 4F-MDMB-BINACA (ED50 = 0.019 mg/kg), 5F-CUMYL-P7AICA (ED50 = 0.13 mg/kg) and EMB-FUBINACA (ED50 = 0.13 mg/kg) each fully substituted for the discriminative stimulus effects of the training dose of Δ9-THC, whereas 5F-AEB produced only a maximum of 67% drug-appropriate responding at 0.5 mg/kg. Higher doses produced piloerection, exophthalmos and convulsions. 4-CN-CUMYL-BUTINACA, 4F-MDMB-BINACA, 5F-CUMYL-P7AICA and EMB-FUBINACA are likely to produce similar subjective effects in humans as those produced by abused synthetic cannabinoids, and may therefore share similar abuse liability. In contrast, 5F-AEB may have a reduced abuse liability given its weaker THC-like discriminative stimulus effects but maybe more dangerous due to the adverse effects observed at doses needed to produce discriminative stimulus effects.

Δ9-Tetrahydrocannabinol discrimination: Effects of route of administration in rats

Cannabis users typically smoke or vape cannabis or ingest it in edibles, whereas cannabinoids are typically administered via injection in rodent research. The present study examined the effects of route of administration (ROA) of Δ⁹-tetrahydrocannabinol (THC), the primary psychoactive constituent of cannabis. Adult female and male Long Evans rats were trained to discriminate intraperitoneal (i.p.) THC from vehicle in a drug discrimination procedure. Following acquisition, dose-effect curves were determined with THC using i.p., oral (p.o.), and subcutaneous (s.c.) injection in both sexes and aerosol exposure in males only, followed by a time course with one dose for each ROA. Both sexes acquired THC discrimination in a similar number of sessions, although baseline response rates were significantly lower in females than males. THC fully substituted for the 3 mg/kg i.p. training dose across all ROA. While potencies were similar for ROA involving first-pass metabolism (i.p. and p.o.), THC potency was lower with s.c. administration. During the time course analysis, aerosol administration had the shortest latency to onset of discriminative stimulus effects and the shortest duration of effect, whereas s.c. administration had the longest duration. The results of this examination of the effects of ROA on an abuse-related effect of THC provide an empirical foundation to facilitate choice of ROA for mechanistic investigation of THC's pharmacology. Further, animal models using translationally relevant ROA may facilitate more accurate predictions of their effects in humans.

Designer drugs: a medicinal chemistry perspective (II)

During 2012-2018, the clandestine manufacture of new psychoactive substances (NPS) designed to circumvent substance control regulations increased exponentially worldwide, with concomitant increase in fatalities. This review focuses on three compound classes identified as synthetic opioids, synthetic amphetamines, and synthetic cannabinoids and highlights the medicinal chemistry precedents utilized by clandestine laboratories to develop new NPS with increased brain penetration, longer duration of action, and greater potency. Chemical approaches to illicit drug abuse treatment options, particularly for opioid use disorder, are also discussed.

Cannabinoid-like effects of five novel carboxamide synthetic cannabinoids

A new generation of novel cannabinoid compounds have been developed as marijuana substitutes to avoid drug control laws and cannabinoid blood tests. 5F-MDMB-PINACA (also known as 5F-ADB, 5F-ADB-PINACA), MDMB-CHIMICA, MDMB-FUBINACA, ADB-FUBINACA, and AMB-FUBINACA (also known as FUB-AMB, MMB-FUBINACA) were tested for in vivo cannabinoid-like effects to assess their abuse liability. Locomotor activity in mice was tested to screen for locomotor depressant effects and to identify behaviorally-active dose ranges and times of peak effect. Discriminative stimulus effects were tested in rats trained to discriminate Δ⁹-tetrahydrocannabinol (3 mg/kg, 30-min pretreatment). 5F-MDMB-PINACA (ED₅₀ = 1.1 mg/kg) and MDMB-CHIMICA (ED₅₀ = 0.024 mg/kg) produced short-acting (30 min) depression of locomotor activity. ADB-FUBINACA (ED₅₀ = 0.19 mg/kg), and AMB- FUBINACA (ED₅₀ = 0.19 mg/kg) depressed locomotor activity for 60-90 min; whereas MDMB-FUBINACA (ED₅₀ = 0.04 mg/kg) depressed locomotor activity for 150 min. AMB-FUBINACA produced tremors at the highest dose tested. 5F-MDMB-PINACA (ED₅₀ = 0.07), MDMB-CHIMICA (ED₅₀ = 0.01 mg/kg), MDMB-FUBINACA (ED₅₀ = 0.051 mg/kg), ADB-FUBINACA (ED₅₀ = 0.075 mg/kg) and AMB-FUBINACA (ED₅₀ = 0.029) fully substituted for the discriminative stimulus effects of Δ⁹-THC following 15-min pretreatment. All 5 compounds decreased locomotor activity and produced discriminative stimulus effects similar to those of Δ⁹-THC, which suggests they may have abuse liability similar to that of Δ⁹-THC. AMB-FUBINACA may have an increased risk of toxicities in recreational users.

The Chemistry and Pharmacology of Synthetic Cannabinoid Receptor Agonist New Psychoactive Substances: Evolution

Synthetic cannabinoid receptor agonists (SCRAs) are the largest and most structurally diverse class of new psychoactive substances (NPS). Although the earliest SCRA NPS were simply repurposed from historical academic manuscripts or pharmaceutical patents describing cannabinoid ligands, recent examples bear hallmarks of rational design. SCRA NPS manufacturers have applied traditional medicinal chemistry strategies (such as molecular hybridization, bioisosteric replacement, and scaffold hopping) to existing cannabinoid templates in order to generate new molecules that circumvent structure-based legislation. Most SCRAs potently activate cannabinoid type 1 and type 2 receptors (CB₁ and CB₂, respectively), with the former contributing to the psychoactivity of these substances. SCRAs are generally more toxic than the Δ⁹-tetrahydrocannabinol (Δ⁹-THC) found in cannabis, and this may be due to ligand bias, metabolism, or off-target activity. This chapter will chart the evolution of recently identified SCRA NPS chemotypes, as well as their putative manufacturing by-products and thermolytic degradants, and describe structure-activity relationships within each class.