Our study support that 2-AG plays a crucial role in cognitive aging, with its decline beginning in middle age and persisting with advancing age. Reduced 2-AG levels is associated with higher neuroinflammation, disrupted glutamine–glutamate/GABA cycle, cognitive deficits. Notably, we provide evidence that CBD, a non-psychoactive component of Cannabis sativa, improves mood and memory, reduces neuroinflammation and preserves cognitive function in aged mice. Furthermore, CBD enhances the expression of DAGL-α, a key enzyme responsible for 2-AG synthesis, suggesting a potential mechanism underlying its neuroprotective effects.

Cognitive aging was assessed using NOR, OiP, and TO tasks, revealing selective impairments in hippocampal- and prefrontal cortex-dependent spatial and temporal memory, while simple object recognition remained largely preserved. These findings are consistent with previous studies showing that aging specifically affects temporal memory, impairing the ability to distinguish past experiences based on temporal context (Kothari et al., 2017; Underwood and Thompson, 2016). To our knowledge, this is the first study to systematically link the temporal dynamics of cognitive decline with eCB. Interestingly, in a mouse model of diabetes, CBD treatment also significantly improved performance across various cognitive and depressive behavioral tasks including NOR and FST (Kesharwani et al., 2025a). Collectively, these findings support CBD as a promising intervention to mitigate age-associated cognitive decline in diverse models.

While our findings implicate eCB signalling in cognitive aging and neuroinflammation, the precise molecular mechanisms underlying the onset and progression of cognitive decline remain incompletely understood. Consistent with our observations (Fig. 5), previous studies have reported that cannabinoid receptors CB1 and CB2 are significantly reduced in aged mice compared to younger cohorts (Berrendero et al., 1998; Liu et al., 2003; Romero et al., 1998).

Genetic evidence further supports a critical role for CB1 receptors in maintaining cognitive function, with their loss accelerating cognitive decline and structural brain alterations (Bilkei-Gorzo et al., 2005; Saravia et al., 2017). Interestingly, a study in an Huntington disease (HD) model showed that the selective loss of CB1 receptors is mechanistically linked to GABAergic deficiency and the progression of cognitive decline (Saravia et al., 2017). Consistent with this, our study found CBD administration increases the expression of GAD67, an enzyme responsible for GABA synthesis (Fig 11). These findings suggest that CBD may improve cognitive deficits by regulating CB1 receptor signalling and GABA levels in aging, and may serve as a potential therapeutic strategy for HD. Importantly, decreased CB1 signalling has been shown to impair microglial phagocytosis, thereby limiting the clearance of cellular debris and exacerbating neuroinflammation (Stella, 2009). In line with this, our data demonstrate a strong association between altered eCB signalling and increased inflammatory responses (Fig. 6). Specifically, aging was associated with activation of the HMGB1–NF-κB–TLR4 signalling pathway, providing a mechanistic link between eCB dysregulation and neuroinflammation. Notably, CBD treatment restored the expression of eCB receptors and attenuated pro-inflammatory signalling in aged mice (Fig. 13), highlighting its therapeutic potential in mitigating cognitive aging and neuroinflammatory processes.

eCB signaling is closely linked to age-related disorders such as AD. Disruption of eCB signaling impairs the excitatory–inhibitory balance and synaptic homeostasis, leading to exacerbated behavioral deficits, particularly under conditions such as social isolation (Li, 2025; Melis et al., 2014; Zhang et al., 2009). These studies support a critical role for eCB signaling in regulating synaptic function in AD. Consistent with this, we found that CBD treatment is beneficial under conditions associated with cognitive dysfunction in normal mice, supporting its potential as a therapeutic agent for AD and associated dementias. Importantly, CBD increased the expression of DAGL-α and CB1/CB2 receptors in aged mice, suggesting that restoration of 2-AG biosynthesis may underlie its neuroprotective effects, including the prevention of memory deficits and neuroinflammation. Thus, our study indicates that targeting eCB signaling remains an attractive strategy for mitigating cognitive aging. In addition, our findings highlight another potential therapeutic avenue, selective enhancement of 2-AG levels. This could be achieved in two ways: by increasing the activity of DAGL-α, which promotes 2-AG synthesis, or by inhibiting monoacylglycerol lipase (MAGL), the enzyme that degrades 2-AG. While the former may require gene therapy approaches that are not readily accessible to all patients, MAGL inhibition represents a more feasible alternative that warrants further investigation.

In summary, our study suggests that targeting the eCB pathway represents a promising therapeutic strategy to improve cognitive deficits associated with normal aging and neurodegenerative disorders such as HD and AD.