CNR1 and neoplasm: In bare contrast, altering the release of the inhibitory neurotransmitter GABA upon deletion of the CB1R gene selectively from forebrain GABAergic/inhibitory neurons [27] (CB1Rfloxed/floxed;Dlx5/6-Cre mice, herein referred to as GABA-CB1R-KO mice) did not cause any overt alteration in tumour growth when using the same experimental setting (Figure 4A).