- 作者: Shu-Ling Liang, Sheng-Chieh Hsu, Jenn-Tser Pan
- 作者服務機構: Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
- 中文摘要: --
- 英文摘要:
Background:
An endogenous dopaminergic (DA) tone acting on D3 receptors has been shown to inhibit tuberoinfundibular (TI) DA neuron activity and stimulate prolactin (PRL) surge in the afternoon of estrogen-primed ovariectomized (OVX+E2) rats. Whether D2 receptor (D2R) is also involved in the regulation of TIDA and PRL rhythms was determined in this study.
Results:
Intracerebroventricular (icv) injection of PHNO, a D2R agonist, in the morning inhibited TIDA and midbrain DA neurons’ activities, and stimulated PRL secretion. The effects of PHNO were significantly reversed by co-administration of raclopride, a D2R antagonist. A single injection of raclopride at 1200 h significantly reversed the lowered TIDA neuron activity and the increased serum PRL level at 1500 h. Dopamine D2R mRNA expression in medial basal hypothalamus (MBH) exhibited a diurnal rhythm, i.e., low in the morning and high in the afternoon, which was opposite to that of TIDA neuron activity. The D2R rhythm was abolished in OVX+E2 rats kept under constant lighting but not in OVX rats with regular lighting exposures. Pretreatment with an antisense oligodeoxynucleotides (AODN, 10 μg/3 μl/day, icv) against D2R mRNA for 2 days significantly reduced D2R mRNAs in central DA neurons, and reversed both lowered TIDA neuron activity and increased serum PRL level in the afternoon on day 3. A diurnal rhythm of D2R mRNA expression was also observed in midbrain DA neurons and the rhythm was significantly knocked down by the AODN pretreatment.
Conclusions:
We conclude that a diurnal change of D2R mRNA expression in MBH may underlie the diurnal rhythms of TIDA neuron activity and PRL secretion in OVX+E2 rats. - 中文關鍵字: --
- 英文關鍵字: Circadian rhythm; 3, 4-dihydroxyphenylacetic acid (DOPAC); Prolactin; Dorsal medial arcuate nucleus; Median eminence; Dopamine receptor