Hess G D, Zagon I S
Department of Anatomy, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
Brain Res Bull. 1988 Apr;20(4):473-8. doi: 10.1016/0361-9230(88)90137-2.
Endogenous opioid systems participate in regulating the development of the nervous system. Opioid antagonists like naltrexone (NTX) perturb the relationship between endogenous opioids and opioid receptors quite effectively and reveal the function(s) of endogenous opioid systems during neuro-ontogeny. In this study, the effects of NTX, as well as the repercussions of modulation of endogenous opioid systems during critical stages of neural ontogeny, have been examined at the electron microscopic level of resolution in infant (10 day) and weanling (21 day) rats. Preweaning rats were subjected to complete (50 mg/kg NTX) or intermittent (1 mg/kg NTX) daily receptor blockade. Extensive ultrastructural examinations were conducted on the external germinal (granule), molecular, Purkinje, internal granule, and medullary layers of the cerebellar cortex. The NTX groups had striking similarities in morphology to that of controls at postnatal days 10 and 21. These results support the hypothesis that endogenous opioid systems act as trophic factors as they regulate growth; their effects on cell growth and survival, however, do not alter the basic ultrastructural morphology of the cells. Moreover, these data further strengthen the validity of paradigms utilizing opioid antagonists to explore the relationship of endogenous opioid-opioid receptor interactions and neural morphogenesis.
内源性阿片系统参与调节神经系统的发育。阿片类拮抗剂如纳曲酮（NTX）能相当有效地扰乱内源性阿片与阿片受体之间的关系，并揭示内源性阿片系统在神经个体发育过程中的功能。在本研究中，已在婴儿期（10日龄）和断奶期（21日龄）大鼠的电子显微镜分辨率水平上，研究了NTX的作用以及在神经个体发育关键阶段对内源性阿片系统进行调节的影响。断奶前的大鼠每天接受完全（50mg/kg NTX）或间歇性（1mg/kg NTX）受体阻断。对小脑皮质的外生发（颗粒）层、分子层、浦肯野层、内颗粒层和髓质层进行了广泛的超微结构检查。NTX组在出生后第10天和第21天的形态与对照组有显著相似之处。这些结果支持了以下假设：内源性阿片系统在调节生长时作为营养因子发挥作用；然而，它们对细胞生长和存活的影响不会改变细胞的基本超微结构形态。此外，这些数据进一步加强了利用阿片类拮抗剂来探索内源性阿片-阿片受体相互作用与神经形态发生关系的范式的有效性。
