Melatonin increases the in situ activity of tyrosine hydroxylase in the mediobasal hypothalamus of male Syrian hamsters

被引:30
作者
Alexiuk, NAM [1 ]
Uddin, M [1 ]
Vriend, J [1 ]
机构
[1] UNIV MANITOBA,DEPT ANAT,WINNIPEG,MB R3E 0W3,CANADA
关键词
melatonin; tyrosine hydroxylase; dopamine; L-DOPA; arcuate nucleus; posterior pituitary;
D O I
10.1016/0024-3205(96)00350-5
中图分类号
R-3 [医学研究方法]; R3 [基础医学];
学科分类号
1001 ;
摘要
The effects of daily late afternoon injections of melatonin on the in situ activity of tyrosine hydroxylase (TH) were examined in the median eminence/arcuate region of the mediobasal hypothalamus (MBH) and the neurointermediate lobe (NIL) of the male Syrian hamster. TH activity was determined in tissue extracts by measuring the accumulation of L-DOPA following administration of the dopa decarboxylase inhibitor, NSD-1015. After 9 weeks of melatonin treatment, highly significant increases in the activity of MBH TH were demonstrated over a 24 hr period, compared to saline-treated controls. Melatonin-induced elevations in TH occurred concomitantly with decreases in tuberoinfundibular dopamine (TIDA) and tuberohypophyseal dopamine (THDA) concentrations. Similar findings were observed in castrated hamsters, indicating that the melatonin-induced increase in TH was not secondary to melatonin-induced changes in circulating levels of gonadal hormones. These data led to the interpretation that melatonin treatment elevated TIDA synthesis either through a direct action on the arcuate nuclei or on neurons impinging on these nuclei.
引用
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页码:687 / 694
页数:8
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