Circular RNA expression profile in the spinal cord of morphine tolerated rats and screen of putative key circRNAs

Microarray analysis for circRNA expression in the spinal cord was conducted and compared between 4 morphine tolerated rats and 4 normal rats Adult male Sprague-Dawley rats in the morphine tolerance group (MT group) received 10 μg intraperitoneal morphine (1 μg/1 μL) twice a day at 08:00–09:00 and 16:00~17:00 for 7 consecutive days.Their cohorts in the normal saline group (NS group, n = 8) received equal volumes of normal saline following the identical protocol. On the 8 th day, one hour after the injection with morphine or saline in the morning,the rats were decapitated under deep anesthesia, and the lumbar enlargements were collected for analysis.