Chavkin C, Goldstein A
Life Sci. 1982;31(16-17):1687-90. doi: 10.1016/0024-3205(82)90186-2.
Spare opiate receptors in the guinea pig ileum have been detected by the use of the opiate receptor alkylating agent beta-chlornaltrexamine (CNA). Treatment of the guinea pig ileum longitudinal muscle in vitro with low concentrations (less than 10nM) of CNA resulted in an irreversible parallel shift to the right of the normorphine log concentration response curve. With increasing concentration of the reagent, the agonist EC50 becomes progressively greater. Finally a point is reached at which the maximal agonist effect decreases, so that parallelism is no longer seen. The maximal parallel shift provides a measure from which one can estimate the spare receptor fraction that is present in untreated tissue. In ilea from normal guinea pigs, roughly 80-90% of the opiate receptors for normorphine were found to be spare. Even after the largest parallel shifts that could be achieved, the naloxone Ke value for antagonism was unchanged, indicating that normorphine acts through spare mu receptors. Ilea from guinea pigs made tolerant by chronic morphine pellet implantation were found to be more sensitive to the effects of CNA treatment; there was a reduction in the number of spare receptors for normorphine. It is suggested that the opiate spare receptor fraction is physiologically modulated to control neuronal sensitivity to opioid effect.
通过使用阿片受体烷基化剂β-氯诺啡胺（CNA），已在豚鼠回肠中检测到备用阿片受体。用低浓度（小于10nM）的CNA体外处理豚鼠回肠纵肌，导致去甲吗啡对数浓度反应曲线不可逆地平行右移。随着试剂浓度的增加，激动剂的半数有效浓度（EC50）逐渐增大。最终达到一个点，此时激动剂的最大效应降低，因此不再呈现平行关系。最大平行位移提供了一种测量方法，据此可以估计未处理组织中存在的备用受体分数。在正常豚鼠的回肠中，发现去甲吗啡的阿片受体中约80 - 90%是备用的。即使在实现最大平行位移后，纳洛酮拮抗作用的平衡解离常数（Ke）值也未改变，表明去甲吗啡通过备用的μ受体起作用。发现通过慢性植入吗啡丸使豚鼠产生耐受性后，其回肠对CNA处理的影响更敏感；去甲吗啡的备用受体数量减少。有人提出，阿片备用受体分数在生理上受到调节，以控制神经元对阿片类药物作用的敏感性。
