初生期麩胺酸鈉處理對成熟後雌鼠松果腺功能的影響

The Effect of Monosodium L-Glutamate (MSG) Treatment During Neonatal Period on the Pineal Function in Young Female Rats

楊秀蘭(Shaw-Lang Yang) ； 許勤(Chin Hsu) ； 張慧秋(Hui-Chiu Chang) ； 許勝光(Hseng-Kuang Hsu)

《The Kaohsiung Journal of Medical Sciences》 8卷8期 (1992/08) Pp. 417-423

https://doi.org/10.6452/KJMS.199208.0417

摘要

麩胺酸鈉(monosodium L-glutamate; MSG)的神經毒性可造成雌鼠第三腦室之核區受損，且破壞視覺路徑，導致生殖內分泌及行為的功能受損。為了探討MSG是否因損壞松果腺之傳入性路徑而加強松果腺的功能，進而抑制生殖行為。本實驗採用兩組實驗動物：１)正常雌鼠及２)MSG處理雌鼠以觀察生殖行為與松果腺之功能變化是否相關。MSG於鼠出生後第一及第三天皮下注射(劑量為4毫克／克體重)，鼠成熟後之生殖行為觀察包含脊柱前凸商(lordosis quotient; LQ)，被動拒絕商(passive rejection quotient; RQ)以及主動引誘行為(solicitation)。松果腺功能之測試則包括測定血清松果色素(melatonin)濃度及松果腺內蛋白激酶A(protein kinase A; PKA)之活性。生殖行為觀察之結果顯示，MSG雌鼠成熟後，接納性與主動引誘行為均顯著低於正常雌鼠。而血清松果色素濃度，MSG鼠與正常鼠在黑暗期之濃度，皆顯著高於光照期，但無論是光照期或黑暗期，MSG鼠與正常鼠兩組間，皆無統計意義之差異。松果腺內蛋白激酶A活性，兩組之間也沒有統計意義之差異。綜合以上結果，初生第一及第三天各皮下注射劑量為4毫克／克體重的胺酸鈉不會響雌鼠松果腺內蛋白激酶A 之活性及血清松果色素之濃度。因此，我們認為雌鼠在MSG神經毒性的影響下，其松果腺蛋白激酶活性及血清松果色素濃度正常，MSG雌鼠接納性及引誘性之降低，並非由於松果腺的抑制功能增高所致。

並列摘要

The pupose of this study is to ex-amine whether monosodium L-glutamate (MSG) influences the function of pinealocytes in female rats. MSG was administered at a does of 4 mg/g body weight to rat pups on days 1 and 3 postnatally. As the rats matured, sexual receptivity as well as proceptivity were observed by testing the lordosis quotient (LQ), rejection quotient (RQ) and solicitation. Pineal function was estimat-ed by measuring the serum level of melatonin and the activity of protein kinase A (PKA) in the pineal gland. Blood samples were withdrawn at light and dark phases for four consecutive days, respectively. The serum concentration of melatonin was deter-mined by radioimmunoassay and the data of each phase were pooled together. The results showed that both the recep-tivity and proceptivity of MSG-treated female rats were significantly lower than that of the control ones. Melatonin levels during the dark phase were sig-nificantly higher than those during the light phase in both control and MSG-treated groups, but whenever in the light or dark phase, the levels of melatonin were the same in both groups. There was no significant difference in PKA activity in the pineal gland be-tween the control and MSG-treated group. These results indicate that MSG used as a neurotoxin to induce hypogonadal status affected neither the PKA activity of pineal gland nor the serum level of melatonin in young fe-male rats. Thus, the decrease in recep-tivity and proceptivity of MSG-treated female rats was not caused by the alter-ation of pineal function.

並列關鍵字

MSG ； melatonin ； PKA