Noun:

1. a neurochemical occurring naturally in the brain and having analgesic properties

endlapn.端搭叠endn.结束；末端；目标；死亡；部分；终点站；端点；半边球场；剩余物，残余；过世v.终止，结束end-to-end QoS architecture端到端的QoS体系结构endometriosis of round ligament圆韧带子宫内膜异位症endothelin-converting enzymes内皮素转化酶endothelial specular microscope内皮窥器显微镜, 内皮透明隔显微镜end radical containing hydrogen含氢端基endophytic epidermoid carcinoma内生性表皮样癌endo-tetrahydrodicyclotadiene四氢双环戊二烯endometriosis of broad ligament阔韧带子宫内膜异位症endocardial regional blood flow心内膜区血流endoscopic rubber band ligation内镜橡皮带结扎

1. One theory is that excessive licking causes endorphin release, causing an addiction to licking.
   一种理论认为舌舔造成内啡肽释放，从而引起嗜舔。