M3 Receptor Pathway Stimulates Rapid Transcription of the CB1 Receptor Activation through Calcium Signalling and the CNR1 Gene Promoter.

In this study, we have investigated a possible mechanism that enables CB/M receptor cross-talk, using SH-SY5Y cells as a model system. Our results show that M receptor activation initiates signaling that rapidly upregulates the CNR1 gene, resulting in a greatly potentiated CB receptor response to agonists. Calcium homeostasis plays an essential intermediary role in this functional CB/M receptor cross-talk. We show that M receptor-triggered calcium release greatly increases CB receptor expression via both transcriptional and translational activity, by enhancing CNR1 promoter activity. The co-expression of M and CB receptors in brain areas such as the nucleus accumbens and amygdala support the hypothesis that the altered synaptic plasticity observed after exposure to cannabinoids involves cross-talk with the M receptor subtype. In this context, M receptors and their interaction with the cannabinoid system at the transcriptional level represent a potential pharmacogenomic target not only for the develop of new drugs for addressing addiction and tolerance. but also to understand the mechanisms underpinning response stratification to cannabinoids.