The influence of cannabidiol (CBD) on brain development is inadequately understood. Since CBD is considered a non-intoxicating drug, it has attracted great interest concerning its potential medical applicability, including in pregnant women and children. Here, we elucidated the response of perinatal rat cortical neurons and astrocytes to CBD at submicromolar (0.1, 0.5, 1, 5 µM) concentrations attainable in humans. The effect of CBD was concentration- and time-dependent and cell-specific. In neurons, 0.1 µM CBD induced an early and transient change in mitochondrial membrane potential (ΔΨm), ATP depletion, and caspase-8 activation, followed by rapid ATP recovery and progressive activation of caspase-9 and caspase-3/7, resulting in early apoptotic cell death with reduction and shortening of dendrites, cell shrinkage, and chromatin condensation. The decrease in neuronal viability, ATP depletion, and caspase activation due to CBD exposure was prevented by transient receptor potential vanilloid 1 (TRPV1) antagonist. In astrocytes, 0.5 µM CBD caused an immediate short-term dysregulation of ΔΨm, followed by ATP depletion with transient activation of caspase-8 and progressive activation of caspase-9 and caspase-3/7, leading to early apoptosis and subsequent necroptosis. In astrocytes, both TRPV1 and cannabinoid receptor 1 (CB₁) antagonists protected viability and prevented apoptosis. Given that CBD is a non-intoxicating drug, our results clearly show that this is not the case during critical periods of brain development when it can significantly interfere with the endogenous cannabinoid system.

Background/Objectives: Synthetic cannabinoid receptor agonists (SCRAs) are associated with severe neurotoxicity, but the cellular mechanisms underlying their effects remain poorly defined. We investigated the effects of Cumyl-PINACA (SGT-24), a carboxamide-type SCRA derived from cumylamine, on rat cortical neurons and astrocytes. Methods: Primary rat cortical neurons and astrocytes were exposed to 1–10,000 nM SGT-24. Metabolic activity, mitochondrial function, morphology, and cell death were evaluated. Selective antagonists of cannabinoid receptor type 1 (CB1), G protein-coupled receptor 55 (GPR55), peroxisome proliferator-activated receptor gamma (PPARγ), and transient receptor potential cation channel subfamily V member 1 (TRPV1) were used to probe the involvement of these receptor pathways. Results: SGT-24 decreased metabolic activity in both cell types in a concentration- and time-dependent manner, with greater potency in neurons (IC₅₀ = 13.2 nM) than in astrocytes (IC₅₀ = 39.8 nM). After 24 h, maximal effects were observed at 100 nM in neurons and 500 nM in astrocytes, reducing metabolic activity by 45.2% and 36.2%, respectively. At these concentrations, mitochondrial membrane potential decreased to 57.6% and 54.1% of control, while cellular ATP levels fell to 51.6% and 52.5%, respectively. Neurons predominantly exhibited early apoptosis (21.9% of cells vs. 3.1% in controls), whereas astrocytes showed mainly 7-aminoactinomycin D (7-AAD)-positive cell death (19.3% vs. 8.2% in controls). Pharmacological inhibition of CB1, TRPV1, and PPARγ attenuated SGT-24-induced metabolic impairment, mitochondrial dysfunction, and apoptosis in neurons, whereas inhibition of CB1 and PPARγ reduced astrocytic toxicity. Conclusions: SGT-24 exerts potent, cell-type-dependent neuroglial toxicity associated with mitochondrial dysfunction and distinct cell death patterns, suggesting the involvement of cannabinoid receptor-dependent and non-cannabinoid signalling mechanisms. The nanomolar potency of SGT-24 underscores the toxicological risk posed by high-potency SCRAs.