Bodnar R J, Portzline T, Nilaver G
Brain Res Bull. 1985 Sep;15(3):299-305. doi: 10.1016/0361-9230(85)90155-8.
Neonatal administration of monosodium glutamate (MSG) produces necrosis of circumventricular structures, including perikarya in the medial-basal hypothalamus that contain beta-endorphin (BEND) and met-enkephalin. Since neonatal MSG treatment alters morphine analgesia, the present study examined neonatal MSG effects upon opioid analgesia observed following either BEND or d-ala d-leu enkephalin (DADL). Rats treated with either MSG or vehicle over the first ten post-natal days, were surgically prepared with a lateral ventricle cannula at 100 days of age. Respective groups received central injections of either BEND (0, 0.1, 0.5 or 1.0 microgram) or DADL (0, 4, 20 or 40 micrograms), and jump thresholds were assessed 15, 30, 45 and 60 min thereafter. Following testing, selected MSG-treated and control animals were prepared for BEND immunocytochemistry. While the magnitude, duration and sensitivity of BEND analgesia on the jump test failed to differ between groups, MSG-treated rats displayed a 10-fold leftward shift in sensitivity and a 200-300% increase in the magnitude of DADL analgesia. Immunocytochemical analysis indicated that MSG treatment depleted perikarya in the medial-basal hypothalamus, periventricular thalamic fibers and periaqueductal gray terminal fields that contained BEND. The differential effects of MSG treatment upon opiate and opioid analgesia are discussed in terms of possible alterations in opiate receptor subpopulations.
新生期给予谷氨酸单钠（MSG）会导致室周结构坏死，包括内侧基底下丘脑含有β-内啡肽（BEND）和甲硫氨酸脑啡肽的神经细胞体。由于新生期MSG处理会改变吗啡镇痛作用，本研究检测了新生期MSG对BEND或D-丙氨酰-D-亮氨酸脑啡肽（DADL）后观察到的阿片类镇痛的影响。在出生后的前10天用MSG或赋形剂处理的大鼠，在100日龄时通过手术植入侧脑室套管。各实验组分别接受脑室内注射BEND（0、0.1、0.5或1.0微克）或DADL（0、4、20或40微克），并在注射后15、30、45和60分钟评估跳跃阈值。测试后，对选定的MSG处理组和对照组动物进行BEND免疫细胞化学检测。虽然BEND镇痛在跳跃试验中的强度、持续时间和敏感性在两组之间没有差异，但MSG处理的大鼠在敏感性上向左偏移了10倍，DADL镇痛强度增加了200-300%。免疫细胞化学分析表明，MSG处理使内侧基底下丘脑、室周丘脑纤维和含有BEND的导水管周围灰质终末场中的神经细胞体减少。根据阿片受体亚群可能的改变，讨论了MSG处理对阿片类和阿片样物质镇痛的不同影响。
