Editorial: The Emerging Role of Endocannabinoids in Synaptic Plasticity, Reward, and Addiction

Endocannabinoids (eCBs) are lipid-signaling molecules that often work in a retrograde fashion. Themost common eCBs are 2-arachidonoylglycerol (2-AG) and anandamide, which bind receptors such as cannabinoid receptor 1 (CB1) and CB2. Endocannabinoid signaling controls synaptic transmission throughout the central nervous system, and is important in modulating activity and behavior in the mesolimbic reward circuit, including the ventral tegmental area (VTA), nucleus accumbens (NAc), and lateral habenula (LHb). In these regions, the eCB system is essential for normal reward learning and for some maladaptive behaviors underlying drug abuse and addiction. Recently identified lipid-signaling eCB-like molecules are also now understood to shape mesolimbic system function and reward-related behaviors. Further elucidating how the eCB system contributes to reward and addiction is especially pertinent given the recent legalization ofmedicinal or recreationalmarijuana throughout the world. Themajor psychoactive component inmarijuana is1-9-tetrahydrocannabinol (THC), which binds CB1. Common effects of THC are short-termmemory loss, appetite stimulation, and reward. There is still much to investigate concerning THC use, particularly the impact of adolescent use, with a focus on long-term alterations in eCB system function and behavioral changes. Further research is required to clarify the role of the endogenous eCB system, and the effect of exogenous CB1 or CB2targeting drugs on mesolimbic function, including synaptic plasticity, to support reward behaviors and addiction. This Research Topic focuses on endogenous eCB system function in the mesolimbic circuit with an emphasis on synaptic plasticity, reward behavior, novel eCB-like molecules, and pain.