Studies utilizing rats demonstrate that opioid receptors and endogenous opioid peptides appear ery early in the CNS deel通过大鼠的研究表明，阿片受体和内源性阿片肽在CNS形成过程中出现很早[2]。
Studies utilizing rats demonstrate that opioid receptors and endogenous opioid peptides appear very early in the CNS dev通过大鼠的研究表明，阿片受体和内源性阿片肽在CNS形成过程中出现很早[2]。