Cannabidiol acts at 5-HT 1A receptors in the human brain: Relevance for treating temporal lobe epilepsy. - GreenMedInfo Summary

Experimental evidence indicates that cannabidiol (CBD) induces anxiolytic and antiepileptic effects through the activation of 5-HTreceptors. These receptors are coupled to Gproteins and induce inhibitory effects. At present, the interaction of CBD with 5-HTreceptors in the human brain is unknown. The aim of this study focused on evaluating the interaction between CBD and 5-HTreceptors in cell membranes obtained from the hippocampus and temporal neocortex of autopsies and patients with drug-resistant mesial temporal lobe epilepsy (DR-MTLE). Cell membranes were isolated from the hippocampus and temporal neocortex of a group of patients with DR-MTLE who were submitted to epilepsy surgery (= 11) and from a group of autopsies (= 11). The [H]-8-OH-DPAT binding assay was used to determine the pharmacological interaction of CBD with 5-HTreceptors. The [S]-GTPγS assay was used to investigate the CBD-induced activation of Gproteins through its action on 5-HTreceptors.The CBD affinity (p) for 5-HTreceptors was similar for autopsies and patients with DR-MTLE (hippocampus: 4.29 and 4.47, respectively; temporal neocortex: 4.67 and 4.74, respectively). Concerning the [S]-GTPγS assay, no statistically significant changes were observed for both hippocampal and neocortical tissue (>0.05) at low CBD concentrations (1 pM to 10μM). In contrast, at high concentrations (100 μM), CBD reduced the constitutive activity of Gproteins of autopsies and DR-MTLE patients (hippocampus: 39.2% and 39.6%, respectively; temporal neocortex: 35.2% and 24.4%, respectively). These changes were partially reversed in the presence of WAY-100635, an antagonist of 5-HTreceptors, in the autopsy group (hippocampus, 59.8%,<0.0001; temporal neocortex, 71.5%,<0.0001) and the group of patients with DR-MTLE (hippocampus, 53.7%,<0.0001; temporal neocortex, 68.5%,<0.001). Our results show that CBD interacts with human 5-HTreceptors of the hippocampus and temporal neocortex. At low concentrations, the effect of CBD upon Gprotein activation is limited. However, at high concentrations, CBD acts as an inverse agonist of 5-HTreceptors. This effect could modify neuronal excitation and epileptic seizures in patients with DR-MTLE.