The compound under investigation, MCH-02, is a synthetic analog of macamides, bioactive fatty acid amides originally derived from Lepidium meyenii, the Peruvian plant known as maca. Macamides have been identified as natural inhibitors of fatty acid amide hydrolase, or FAAH, the enzyme responsible for degrading anandamide, one of the brain’s principal endocannabinoids. By inhibiting FAAH, compounds like MCH-02 indirectly enhance endocannabinoid tone, an approach that has shown anticonvulsant effects in some experimental models. The specific molecule tested, N-(8Z-heptadecen-1-yl)-O-(3-pyridylmethyl) carbamate, demonstrated in vitro FAAH-inhibitory activity, raising hopes that it might protect against the progressive development of seizure susceptibility. The research team, led by Yessenia Yauri-Huaman, Rodrigo Caceres-Robles, and Luis F. Pacheco-Otalora, hypothesized that FAAH inhibition by MCH-02 would modulate endocannabinoid tone in a context-dependent manner, leading to differential effects on hippocampal network excitability across stages of epileptogenesis.

To test this hypothesis, the researchers employed the pentylenetetrazol, or PTZ, kindling model in rats, a widely used experimental paradigm that captures the temporal evolution of progressive seizure susceptibility. Unlike acute seizure paradigms, PTZ kindling reproduces the gradual transformation of a normal brain into a hyperexcitable state through repeated subconvulsive stimulation. In this study, 39 male Sprague–Dawley rats received either vehicle or MCH-02 at 1 mg/kg intraperitoneally one hour before each PTZ administration throughout the kindling protocol. The dose was selected based on pilot experiments evaluating 0.1, 1, and 10 mg/kg in an acute PTZ seizure model, which indicated that 1 mg/kg produced the most consistent biological response without observable adverse effects. Animals were monitored using a modified Racine scale adapted to the behavioral manifestations observed in this model, ranging from behavioral arrest at stage 1 to generalized tonic–clonic seizures at stage 5. Full kindling acquisition was defined as two consecutive Racine stage 5 seizures, which animals typically reached after 17 PTZ injections over 35 days.

The principal finding of the study is a striking dissociation between hippocampal molecular remodeling and functional seizure outcomes. MCH-02 did not prevent PTZ-induced progressive seizure susceptibility. More unexpectedly, the compound transiently worsened seizure severity during the initial phases of kindling acquisition. Cumulative link mixed-model analysis identified a significant group effect on kindling progression, and post hoc comparisons revealed a higher Racine score in the MCH-02 plus PTZ group compared to the vehicle plus PTZ group during the first trial. No significant between-group differences were detected in subsequent trials, suggesting that the proconvulsant effect was restricted to the earliest stage of network remodeling. Survival probability did not differ significantly among groups, and the researchers observed no evidence of a protective effect on survival. Latency to the onset of Racine stage 4 seizures also showed no significant group effect, providing no evidence that MCH-02 altered the temporal course of seizure development relative to vehicle.

On the molecular level, however, MCH-02 clearly engaged its intended target pathways. Using RT-qPCR and Western blot analyses of the hippocampal CA1, CA3, and dentate gyrus subregions, the researchers found that chronic MCH-02 administration increased mRNA levels of FAAH, Cnr1, and Napepld in the CA1 region. FAAH mRNA levels showed a significant group effect, with post hoc analysis revealing a notable increase in the MCH-02 plus PTZ group compared to both vehicle-treated groups. Similarly, Cnr1 mRNA levels, which encode the CB1 cannabinoid receptor, were higher in the MCH-02 plus PTZ group relative to vehicle controls. Napepld, which encodes the enzyme responsible for synthesizing 2-arachidonoylglycerol, another major endocannabinoid, was also elevated in MCH-02-treated animals. In CA3, the only gene transcript notably affected was Napepld, which showed decreased expression in both MCH-02 groups. No significant changes were observed in the dentate gyrus at the transcript level.

Protein-level analyses revealed a more complex picture. In CA1, CB1 receptor expression showed a strong overall group effect, with higher levels in both PTZ-treated groups compared to vehicle plus saline controls. BKα1 expression, the pore-forming subunit of large-conductance calcium-activated potassium channels, was also significantly affected by group, with higher levels observed in vehicle plus PTZ animals compared to vehicle plus saline controls. In CA3, FAAH was the only protein showing a significant overall group effect, with lower expression in both MCH-02 groups compared to vehicle plus PTZ. In the dentate gyrus, significant group effects were detected for FAAH, CB1 receptor, and BKα1, though the specific pairwise comparisons varied. Notably, transcript-level differences were not consistently accompanied by corresponding differences in protein abundance. The higher FAAH mRNA in MCH-02 plus PTZ animals was not reflected in a significant group effect on FAAH protein, and the elevated Cnr1 mRNA in MCH-02 plus PTZ relative to vehicle plus PTZ was not accompanied by a significant protein-level difference in that comparison.

The involvement of BK channels adds a novel dimension to these findings. BK channels are critical regulators of membrane excitability and action potential repolarization, and alterations in their function have been implicated in seizure susceptibility and epilepsy pathophysiology. Previous studies have demonstrated that endocannabinoids, particularly anandamide, can modulate BK channel activity directly and indirectly, suggesting potential interactions between endocannabinoid signaling and intrinsic excitability mechanisms. In the present study, MCH-02 administration was associated with increased Kcnma1 expression, the gene encoding the BK channel α1 subunit, and alterations in BKα1 protein levels, particularly within the CA1 region. These findings suggest that endocannabinoid-associated molecular remodeling may extend to ion channel systems involved in the regulation of excitability. However, no electrophysiological recordings were performed to evaluate BK currents, neuronal firing properties, or intrinsic excitability, so the functional significance of these changes remains uncertain.

Behavioral assessments of learning and memory further reinforced the dissociation between molecular adaptation and seizure protection. The Barnes maze test revealed complex interactions among group, cohort, and timepoint during training, but by day 4 there were no significant differences among groups, and the probe test did not reveal treatment-related differences in target-quadrant occupancy. The novel object recognition test showed a significant and positive increase in the discrimination index for the MCH-02 plus PTZ group compared to the vehicle plus PTZ group on the test day, but this difference was restricted to cohort 1 and was not reproduced in cohort 2, leading the researchers to interpret it as a cohort-specific effect rather than evidence of a general treatment-related improvement in recognition memory. Total distance traveled and mean velocity during behavioral testing showed no significant differences among groups, cohorts, or days, indicating that locomotor activity was not differentially affected.

The researchers propose several mechanisms that might explain why substantial endocannabinoid-associated molecular remodeling did not translate into sustained protection against kindling progression. One possibility involves the state-dependent nature of cannabinoid signaling. Experimental epilepsy models have demonstrated early CB1 receptor internalization and downregulation following intense seizure activity, followed by compensatory receptor redistribution and upregulation during later stages. Within this framework, the early proconvulsant effects observed after MCH-02 administration may reflect a mismatch between enhanced endocannabinoid tone and reduced functional CB1 receptor availability during the initial phases of network remodeling. Under these conditions, increased endocannabinoid signaling may fail to engage protective inhibitory mechanisms efficiently, thereby contributing to transient network instability. Another possibility involves neuroinflammatory and glial pathways, which are increasingly recognized as important components of the progressive network remodeling associated with recurrent seizure activity. Because FAAH regulates the availability of anandamide and other N-acylethanolamines, its inhibition may influence these processes through mechanisms extending beyond neuronal CB1-mediated modulation of synaptic transmission.

The study’s authors emphasize that their findings should be interpreted as evidence of hippocampal neurobiological remodeling rather than proof of therapeutic efficacy. The principal conclusion that MCH-02 did not provide sustained protection against PTZ-induced seizure susceptibility is supported not by an isolated non-significant comparison but by the longitudinal behavioral pattern: seizure progression remained broadly comparable between the PTZ-treated groups throughout the protocol, while MCH-02 produced a significant transient increase in seizure severity during the initial phase. The researchers acknowledge important limitations, including the absence of direct measurements of brain concentrations of MCH-02, pharmacokinetic parameters, in vivo FAAH enzymatic inhibition, endocannabinoid concentrations, CB1 receptor occupancy, and functional BK-channel activity. Molecular measurements represent endpoint adaptations following completion of the kindling protocol and therefore cannot establish the temporal sequence or causal relationships among FAAH modulation, endocannabinoid system remodeling, BK-channel-associated changes, and seizure progression. Future studies combining plasma and brain pharmacokinetics, direct FAAH activity measurements, endocannabinoid profiling, functional electrophysiology, quantitative glial assessments, and systematic longitudinal EEG monitoring will be needed to test the proposed mechanisms and establish whether alternative MCH-02 regimens offer reproducible benefit in chronic epilepsy models.

Subject of Research: Neuroscience

Article Title: MCH-02, a synthetic macamide analog with in vitro FAAH-inhibitory activity, modulates hippocampal endocannabinoid system and BK channel expression without preventing PTZ-induced progressive seizure susceptibility in rats

Article References: Yauri-Huaman, Y., Caceres-Robles, R., Becerra Flores, C., Garay-Malpartida, M., Medina-Saldivar, C., & Pacheco-Otalora, L. F. (2026). MCH-02, a synthetic macamide analog with in vitro FAAH-inhibitory activity, modulates hippocampal endocannabinoid system and BK channel expression without preventing PTZ-induced progressive seizure susceptibility in rats. Frontiers in Neurology, 17, Article 1843264. https://doi.org/10.3389/fneur.2026.1843264

Image Credits: AI Generated

DOI: 10.3389/fneur.2026.1843264

Keywords: epilepsy, endocannabinoid system, FAAH inhibitor, macamide, BK channels, PTZ kindling, hippocampus, seizure susceptibility, MCH-02, synthetic, analog, vitro