Involvement of dopamine D2 receptor in the diurnal changes of tuberoinfundibular dopaminergic neuron activity and prolactin secretion in female rats

Journal of Biomedical Science

Jenn-Tser Pan²  Sheng-Chieh Hsu³  Shu-Ling Liang¹ 

[1] Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan 33302, Taiwan;Department of Biological Sciences, Oakland University, Rochester, MI 48309, USA;Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan 33302, Taiwan

关键词: Dopamine receptor;    Median eminence;    Dorsal medial arcuate nucleus;    Prolactin;    3, 4-dihydroxyphenylacetic acid (DOPAC);    Circadian rhythm;   

Others  :  817647
DOI  :  10.1186/1423-0127-21-37

 received in 2014-02-11, accepted in 2014-04-29,  发布年份 2014

【 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.

【 授权许可】

   
2014 Liang et al.; licensee BioMed Central Ltd.

【 图 表 】

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