Mauro L J, Elde R P, Youngren O M, Phillips R E, el Halawani M E
Department of Animal Science, University of Minnesota, St. Paul 55108.
Endocrinology. 1989 Oct;125(4):1795-804. doi: 10.1210/endo-125-4-1795.
Vasoactive intestinal peptide (VIP) has potent PRL-releasing activity, but its physiological role in the regulation of PRL release during the avian reproductive cycle is not known. We used indirect immunofluorescence to determine if changes in hypothalamic VIP are associated with the shifts in circulating PRL during the reproductive cycle of the domestic turkey. In the naturally hyperprolactinemic incubating hen, the majority of VIP immunoreactivity (VIP-IR) existed within neurons of the infundibular nuclear complex (INF) and fibers in the external layer of the median eminence. Within the INF, the numbers of VIP-IR cells increased during the cycle, paralleling increases in serum PRL. In the reproductively inactive, nonphotostimulated hen with low serum PRL, essentially no positive cells were noted, whereas the incubating hen exhibited 32.1 +/- 2.2 cells/pair of adjacent sections in the anterior INF and 59.6 +/- 2.0 cells in the posterior INF. Exposure of inactive hens to a stimulatory photoperiod resulted in a 2.6-fold increase in serum PRL with the appearance of VIP-IR cells in the INF. During laying and incubation, further increases were observed in the number of positive cells in the INF and serum PRL as well as a greater fiber density in the median eminence. To further examine the association between changes in VIP-IR and serum PRL, circulating PRL was artificially lowered by depriving incubating hens of their nests for 0, 2, 5, and 10 days. On day 2 of nest deprivation, serum PRL declined markedly to 12% of day 0 levels, with VIP-IR cell numbers at 64% and 46% in the anterior and posterior INF, respectively. By day 10, birds exhibited cell numbers in the INF averaging 20% of those observed in the day 0 incubating hens, with serum PRL at 6% of day 0 levels. The results of these studies indicate a possible causal relationship between hypothalamic VIP and changes in PRL secretion during the avian reproductive cycle, providing a basis for further research on the importance of this peptide as well as factors responsible for the modulation of its expression in hypothalamic INF neurons.
血管活性肠肽（VIP）具有强大的促催乳素释放活性，但其在禽类生殖周期中调节催乳素释放的生理作用尚不清楚。我们采用间接免疫荧光法来确定在家禽火鸡的生殖周期中，下丘脑VIP的变化是否与循环催乳素的变化相关。在自然高催乳素血症的抱窝母鸡中，大多数VIP免疫反应性（VIP-IR）存在于漏斗核复合体（INF）的神经元内以及正中隆起外层的纤维中。在INF内，VIP-IR细胞的数量在周期中增加，与血清催乳素的增加平行。在生殖不活跃、未受光刺激且血清催乳素水平低的母鸡中，基本未观察到阳性细胞，而抱窝母鸡在前INF中每对相邻切片显示32.1±2.2个细胞，在后INF中为59.6±2.0个细胞。将不活跃母鸡暴露于刺激性光周期下，血清催乳素增加2.6倍，同时INF中出现VIP-IR细胞。在产蛋和抱窝期间，观察到INF中阳性细胞数量、血清催乳素进一步增加，以及正中隆起处纤维密度更大。为了进一步研究VIP-IR变化与血清催乳素之间的关联，通过剥夺抱窝母鸡的窝0、2、5和10天来人为降低循环催乳素。在剥夺窝的第2天，血清催乳素显著下降至第0天水平的12%，前INF和后INF中VIP-IR细胞数量分别为64%和46%。到第10天，禽类INF中的细胞数量平均为第0天抱窝母鸡观察值的20%，血清催乳素为第0天水平的6%。这些研究结果表明，下丘脑VIP与禽类生殖周期中催乳素分泌变化之间可能存在因果关系，为进一步研究该肽的重要性以及负责调节其在下丘脑INF神经元中表达的因素提供了基础。
