LESIONS OF THE IODOMELATONIN-BINDING SITES OF THE MEDIOBASAL HYPOTHALAMUS SPARE THE LACTOTROPIC, BUT BLOCK THE GONADOTROPIC RESPONSE OF MALE SYRIAN-HAMSTERS TO SHORT PHOTOPERIOD AND TO MELATONIN
LESIONS OF THE IODOMELATONIN-BINDING SITES OF THE MEDIOBASAL HYPOTHALAMUS SPARE THE LACTOTROPIC, BUT BLOCK THE GONADOTROPIC RESPONSE OF MALE SYRIAN-HAMSTERS TO SHORT PHOTOPERIOD AND TO MELATONIN
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DOI：
10.1210/en.136.1.144
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发表时间：
1995-01-01
期刊：
影响因子：
4.8
通讯作者：
HASTINGS, MH
中科院分区：
文献类型：
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作者：
MAYWOOD, ES;HASTINGS, MH
本研究的目的是确定是否碘美拉通素结合位点内的视前区（POA）或下丘脑内侧基底部（MBH）是必不可少的光周期控制的季节性繁殖在雄性叙利亚仓鼠。动物接受针对POA（POA-X; n = 11）或MBH（MBH-X; n = 12）的假手术或双侧电解损伤，然后在转移到短光周期（SD; 8 h光照和16 h黑暗）之前维持长日照（16 h光照和8 h黑暗）至少4周。每4周记录一次损伤和完整仓鼠的左侧睾丸的经阴囊宽度和血清睾酮（实验1）、PRL和LH（实验2）水平，以监测其生殖状态。MBH的损伤，而不是POA的损伤，消除了SD诱导的性腺反应（SD 12周后左侧睾丸的经阴囊宽度：MBH-X，10.0 +/- 0.2 mm;假手术，4.6 +/- 0.1 mm; POA-X，4.0 +/- 0.1 mm;假手术，4.1 +/- 0.1 mm）。类似地，MBH病变阻止了血清LH浓度的降低（12周SD后的血清LH：MBH-X，0.74 +/- 0.2 ng/ml;假手术，0.25 +/- 0.1 ng/ml）。然而，两种病变都不能阻止SD诱导的血清PRL下降（SD 12周后的血清PRL：MBH-X，4.7 +/- 1.0 ng/ml;假手术，3.1 +/- 0.1 ng/ml; POA-X，2.0 +/- 0.1 ng/ml;假手术，2.0 +/- 0.1 ng/ml）。为了排除MBH损伤通过破坏夜间褪黑激素产生而阻止性腺退化的可能性，将MBH-X动物切换到长日照期，切除松果体，并安装皮下插管，每天一次输注褪黑激素（500 ng/10 h）或盐水（50 μ l/h），持续6周。接受相同输注的一组神经完整的松果体切除的对照动物显示出褪黑激素治疗的预期性腺退化，而接受盐水媒介物的那些具有大睾丸（褪黑激素，0.5 +/- 0.1 g;盐水，3.3 +/- 0.3 g）。此外，输注6周后，完整褪黑激素输注仓鼠的血清LH和PRL浓度显著降低（LH：褪黑激素，0.2 +/- 0.04 ng/ml;生理盐水，1.3 +/- 0.1 ng/ml; PRL：褪黑激素，2.2 +/- 0.2 ng/ml;生理盐水，16.9 +/- 3.1 ng/ml）。与完整对照相比，输注褪黑激素的MBH-X动物均未表现出性腺退化（MBH-X：褪黑激素，2.8 +/- 0.5 g;盐水，2.9 +/- 0.5 g）。此外，注射褪黑激素或生理盐水的MBH-X动物之间的血清LH浓度没有显著差异（褪黑激素，0.78 +/-0.2ng/ml;生理盐水，0.70 +/-0.1ng/ml），而褪黑激素的输注对MBH-X动物的血清PRL浓度确实有显著影响（褪黑激素，2.4 +/-0.3ng/ml;盐水，8.0 +/-1.0ng/ml）。这些结果表明，一个完整的MBH，而不是POA，是必不可少的光周期控制促性腺激素活性的叙利亚仓鼠。这两个网站是必不可少的光周期控制的催乳轴。这些数据是一致的假设，褪黑激素的行为通过褪黑激素结合位点的MBH控制光周期的节奏的繁殖。
The aim of this study was to determine whether the iodomelatonin-binding sites identified within the preoptic area (POA) or mediobasal hypothalamus (MBH) are essential for the photoperiodic control of seasonal reproduction in male Syrian hamsters. Animals received sham or bilateral electrolytic lesions directed toward either the POA (POA-X; n = 11) or MBH (MBH-X; n = 12) and were then maintained on long days (16 h of light and 8 h of darkness) for at least 4 weeks before transfer to a short photoperiod (SD; 8 h of light and 16 h of darkness). The transscrotal width of the left testis and serum testosterone (Exp 1), PRL, and LH (Exp 2) levels were recorded every 4 weeks in lesioned and intact hamsters to monitor their reproductive state. Lesions of the MBH, but not the POA, abolished the SD-induced gonadal responses (transscrotal width of the left testis after 12 weeks of SD: MBH-X, 10.0 +/- 0.2 mm; sham, 4.6 +/- 0.1 mm; POA-X, 4.0 +/- 0.1 mm; sham, 4.1 +/- 0.1 mm). Similarly, the decrease in serum LH concentrations was prevented by lesions of the MBH (serum LH after 12 weeks SD: MBH-X, 0.74 +/- 0.2 ng/ml; sham, 0.25 +/- 0.1 ng/ml). However, neither lesion prevented the SD-induced decline in serum PRL (serum PRL after 12 weeks SD: MBH-X, 4.7 +/- 1.0 ng/ml; sham, 3.1 +/- 0.1 ng/ml; POA-X, 2.0 +/- 0.1 ng/ml; sham, 2.0 +/- 0.1 ng/ml). To exclude the possibility that the lesion to the MBH prevented gonadal regression through disruption of nocturnal melatonin production, MBH-X animals were switched to a long day photoperiod, pinealectomized, and fitted with a sc cannula for the infusion of either melatonin (500 ng/10 h) or saline (50 mu l/h) once daily for 6 weeks. A group of neurally intact, pinealectomized control animals that received the same infusions showed the expected gonadal regression with melatonin treatment, whereas those receiving saline vehicle had large testes (melatonin, 0.5 +/- 0.1 g; saline, 3.3 +/- 0.3 g). Furthermore, after 6 weeks of infusions, serum LH and PRL concentrations in intact melatonin-infused hamsters were significantly reduced (LH: melatonin, 0.2 +/- 0.04 ng/ml; saline, 1.3 +/- 0.1 ng/ml; PRL: melatonin, 2.2 +/- 0.2 ng/ml; saline, 16.9 +/- 3.1 ng/ml). In contrast to the intact controls, none of the MBH-X animals infused with melatonin exhibited gonadal regression (MBH-X: melatonin, 2.8 +/- 0.5 g; saline, 2.9 +/- 0.5 g). In addition, serum LH concentrations were not significantly different between MBH-X animals infused with either melatonin or saline (melatonin, 0.78 +/- 0.2 ng/ml; saline, 0.70 +/- 0.1 ng/ml), whereas infusions of melatonin did have a significant effect on serum concentrations of PRL in MBH-X animals (melatonin, 2.4 +/- 0.3 ng/ml; saline, 8.0 +/- 1.0 ng/ml). These results show that an intact MBH, but not POA, is essential for the photoperiodic control of gonadotropic activity in the Syrian hamster. Neither site is essential for photoperiodic control of the lactotropic axis. The data are consistent with the hypothesis that melatonin acts via the melatonin-binding sites of the MBH to control photoperiodic rhythms of reproduction.