['Cannabidiol (CBD) has emerged as an interesting compound with therapeutic potential in several CNS disorders. However, whether it can modulate synaptic activity in the CNS remains unclear. Here, we have investigated whether CBD modulates synaptic transmission in rat hippocampal cultures and acute slices.', 'The effect of CBD on synaptic transmission was examined in rat hippocampal cultures and acute slices using whole cell patch clamp and standard extracellular recordings respectively.', 'Cannabidiol decreased synaptic activity in hippocampal cultures in a concentration-dependent and Pertussis toxin-sensitive manner. The effects of CBD in culture were significantly reduced in the presence of the cannabinoid receptor (CB(1) ) inverse agonist, LY320135 but were unaffected by the 5-HT(1A) receptor antagonist, WAY100135. In hippocampal slices, CBD inhibited basal synaptic transmission, an effect that was abolished by the proposed CB(1) receptor antagonist, AM251, in addition to LY320135 and WAY100135.'] Does cannabidiol inhibit synaptic transmission in rat hippocampal cultures and slices via multiple receptor pathways?