Endocannabinoid Enhancement via MAGL Inhibition in CDKL5 Deficiency: Selective Cellular Benefits and Constrained Functional Impact in Cdkl5 KO Mice

CDKL5 Deficiency Disorder (CDD) is a severe neurodevelopmental encephalopathy char-acterized by early disruptions of synaptic maturation and network stability, leading to persistent motor, cognitive, and behavioral impairments. Given the role of the endocan-nabinoid system in synaptic development, neuroinflammation, and neuronal resilience, we investigated whether chronic enhancement of endogenous 2-arachidonoylglycerol (2-AG) signaling via monoacylglycerol lipase (MAGL) inhibition could mitigate key pathological features in Cdkl5 knockout (KO) mice. Using an intermittent 6-week treat-ment, the MAGL inhibitor JZL184 robustly increased plasma 2-AG levels, inhibited MAGL activity, and activated CB1-AKT signaling without evidence of receptor desensiti-zation. Despite this clear pharmacodynamic efficacy, behavioral improvement was lim-ited: neither dose rescued core behavioral deficits, although the higher dose selectively re-duced stereotypic jumping and modestly improved cue-dependent associative memory. At the cellular level, JZL184 induced biologically meaningful effects, partially restoring dendritic spine maturation and increasing neuronal survival in the vulnerable CA1 hip-pocampal region. In contrast, microglial responses were dose-dependent and divergent, with the lower dose exerting anti-inflammatory effects, while the higher dose increased cortical microglial density and AIF-1 expression, suggesting engagement of compensatory or off-target mechanisms. Overall, these findings show that MAGL inhibition activates neuroprotective pathways and ameliorates select structural deficits in Cdkl5 KO mice, but is insufficient to reverse established behavioral abnormalities, highlighting the limits of endocannabinoid enhancement and the need for developmentally timed or multimodal therapeutic strategies in CDD.