How cannabis and adenosine receptors team up to grow new brain cells

Adult neurogenesis is a tightly regulated process affected by both cannabinoid receptors (CB1 and CB2) and adenosine 2A (A2A) receptors, both of which modulate neural progenitor cell activity. While emerging evidence suggests an interaction between these neuromodulatory systems, the extent and mechanism of their interplay in regulating neurogenesis remain unclear. Using a combination of in vivo and in vitro approaches together with pharmacological and receptor/binding assays, we investigated the crosstalk between A2A and CB receptors in regulating hippocampal neurogenesis. In vivo administration of WIN55212-2, a non-selective cannabinoid receptor agonist, increased hippocampal cell proliferation and immature neuron formation, an effect abolished by istradefylline, a selective A2A receptor antagonist. In vitro, activation of CB2 or A2A receptors promoted self-renewing divisions of hippocampal-derived neural progenitor cells. A2A receptor antagonism impaired CB2 receptor-mediated effects, whereas CB1/CB2 antagonism blocked A2A-mediated effects. Co-activation of CB1 or CB2 receptors with A2A receptors promoted a significant increase in cell proliferation. Notably, the proneurogenic effects mediated by CB1 or CB2 receptor agonists were blocked by A2A receptor antagonism, while A2A receptor-mediated actions on neuronal differentiation were blocked by CB1 or CB2 receptor antagonists. Finally, receptor-binding assays showed that A2A and CB1 receptors form heteromers in the mouse hippocampus, suggesting that their functional interaction may involve direct receptor-receptor crosstalk. Taken together, these findings suggest a crosstalk between the adenosinergic and cannabinergic systems responsible for regulating hippocampal progenitor dynamics. The identification of CB1-A2A receptor heteromerization provides new insights into the molecular basis of neurogenic modulation and highlights a promising avenue for the development of novel proneurogenic therapeutic strategies.