Role of endocannabinoids and TRPV1 channels in the bioelectric activity of hippocampal neurons

It has been reported that endocannabinoid system is an important player in the regulation of neuronal bioelectrical activity, relying on receptor-mediated mechanisms. Amongst these, Cannabinoid receptor type 1 (CB1r) and Transient Receptor Potential Vanilloid type 1 (TRPV1) are both modulated by endocannabinoids, involved in the transduction of stimuli in the pre-synaptic neuron and prompt downstream pathways in the post-synaptic neuron. To investigate the role of CB1r/TRPV1 interplay, we applied whole-cell patch clamp technique to visualize the eventual variations in terms of membrane current and action potentials induced by pharmacological manipulation in rat hippocampal neurons. We modulated the activity of the CB1r and TRPV1 exploiting anandamide (AEA), CB1r and TRPV1 agonist, capsaicin (CAP), a TRPV1 agonist and capsazepine (CPZ), a TRPV1 antagonist. Our data show that AEA influences steady membrane current with respect to controls. Furthermore, drug application significantly modifies action potentials amplitude, duration and frequency. In particular, the co-treatment of AEA and CPZ increases the amplitude of action potentials, reduces their duration and thus increases their frequency. These preliminary results support the involvement of TRPV1 in the cannabinoid modulation of the bioelectrical activity in rat hippocampal neurons. Indeed, the concurrent blockade of these channels and activation of CBr influences basic properties of neuronal function.