Feng Yi, Zhao Hong, An Xiao-Fei, Ma Su-Lan, Chen Bo-Ying
Department of Neurobiology and Integrative Medicine, Shanghai Medical College of Fudan University, P.O. Box 291, 138 Yi-Xue-Yuan Road, Shanghai 200032, PR China.
Neurosci Lett. 2007 May 23;419(1):38-42. doi: 10.1016/j.neulet.2007.03.069. Epub 2007 Apr 11.
Prolactin releasing peptide (PrRP) is a neuropeptide with 31 or 20 amino acid residues and regarded as a potent and specific stimulator of pituitary prolactin. PrRP immunoreactive (PrRP-ir) neurons and mRNA are found in medulla oblongata and hypothalamus and the fibers containing PrRP are widely distributed in rat brains. Therefore, it is postulated that PrRP might act as a neurohormone or a neurotransmitter as well as a neuromodulator in the brain. In the present study, we probed the expression of brain PrRP in the estrous cycle of female rats and the relationship between brain PrRP and GnRH. Female rats were divided into four groups: the diestrus, the proestrus, the estrus and the metaestrus, which were identified by the vaginal cytological examination. Immunohistochemistry, reverse transcriptase-polymerase chain reaction (RT-PCR) and immunofluorescent double labeling histochemistry combining confocal laser scanning microscope (CLSM) were used. The results showed that PrRP immunoreactive neurons in nucleus of solitary tract (NTS) and ventrolateral reticular nucleus (VLRN) in the proestrus were less than those in the diestrus, the estrus and the metaestrus. Similarly, the relative optical density of PrRP-ir fibers of the bed nucleus of stria terminalis (BST) in the proestrus was decreased compared with those in other three groups. However, the brain PrRPmRNA level was higher in the proestrus and estrus than those in the metaestrus and diestrus. We also observed the co-localization of GPR10-immunoreactive (GPR10-ir) and GnRH-immunoreactive (GnRH-ir) neurons in hypothalamic medial preoptic area (MPO). The present results provide morphological evidences that PrRP in the female rat brains might participate in the regulation of the rat estrous cycle at least in a direct way.
催乳素释放肽（PrRP）是一种含有31个或20个氨基酸残基的神经肽，被认为是垂体催乳素的一种强效且特异性的刺激物。在延髓和下丘脑发现了催乳素释放肽免疫反应性（PrRP-ir）神经元和mRNA，并且含有PrRP的纤维广泛分布于大鼠脑内。因此，推测PrRP在脑内可能作为一种神经激素、神经递质以及神经调质发挥作用。在本研究中，我们探究了雌性大鼠发情周期中脑内PrRP的表达以及脑内PrRP与促性腺激素释放激素（GnRH）之间的关系。雌性大鼠被分为四组：间情期、动情前期、动情期和动情后期，通过阴道细胞学检查对其进行鉴定。采用免疫组织化学、逆转录聚合酶链反应（RT-PCR）以及结合共聚焦激光扫描显微镜（CLSM）的免疫荧光双标记组织化学方法。结果显示，动情前期孤束核（NTS）和腹外侧网状核（VLRN）中的PrRP免疫反应性神经元少于间情期、动情期和动情后期。同样，与其他三组相比，动情前期终纹床核（BST）中PrRP-ir纤维的相对光密度降低。然而，脑内PrRPmRNA水平在动情前期和动情期高于动情后期和间情期。我们还观察到下丘脑内侧视前区（MPO）中G蛋白偶联受体10免疫反应性（GPR10-ir）神经元和GnRH免疫反应性（GnRH-ir）神经元的共定位。目前的结果提供了形态学证据，表明雌性大鼠脑内的PrRP可能至少以直接的方式参与大鼠发情周期的调节。
