GPR18 and infection: The binding of cannabinoids to their receptors impacts signaling pathways including those related to calcitonin gene-related peptide (CGRP), responsible for vasodilation, nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB), which regulates host immune response in the face of infection, G protein-coupled receptor 18 (GPR18), inducing apoptosis of proinflammatory macrophages [26] and peroxisome proliferator-activated receptors (PPARs), nuclear transcriptions factors that also play a role in modulation of pain sensation [27].