S1PR1 and neuropathic pain: In a mouse model of neuropathic pain, S1PR1 antagonists blocked the development of morphine tolerance and prevented morphine-induced neuropathic pain by reversing S1P-induced neuroinflammation including activation of mitogen-activated protein kinase p38 and NF-κB, and increased expression of inflammatory cytokines (Doyle et al., 2020b).