Buntin J D, Becker G M, Ruzycki E
Department of Biological Sciences, University of Wisconsin, Milwaukee 53201.
Horm Behav. 1991 Sep;25(3):424-44. doi: 10.1016/0018-506x(91)90012-7.
Systemic administration of ovine prolactin (PRL) has been previously reported to stimulate parental feeding behavior toward 7-day-old foster squabs by nonbreeding ring doves with previous breeding experience. The first of the present experiments reexamined this claim in experienced, nonbreeding birds given test squabs of different ages. Each visually isolated male and female dove was given twice-daily subcutaneous injections of ovine PRL or vehicle for 7 days and then tested for parental responses toward a single 1-3, 6-8, or 11- to 13-day-old foster squab. Prolactin significantly increased the incidence or frequency of parental regurgitation-feeding episodes in tests with all three squab age groups and, in addition, increased the incidence of parental feeding invitations (squab-oriented bill openings) in tests with 6- to 8-day-old squabs. A second study explored the degree to which PRL can act directly on the central nervous system to facilitate parental activity in the absence of peripheral cues generated from PRL-induced changes in other target organs, such as those associated with crop sac growth and distension. In this experiment, 6- to 8-day-old test squabs were used to determine if parental behavior is enhanced by twice-daily intracerebroventricular (ICV) injections of PRL in doses below those required to stimulate peripheral target organs. Injection schedules and behavior testing procedures were the same as those used in Experiment 1. However, half of the ICV PRL-treated and ICV vehicle-treated birds were food deprived for 16 hr before and during the test in order to control for PRL-induced hyperphagia and resulting crop sac distension, which could confound the results by generating peripheral stimuli conductive to the display of regurgitation-feeding behavior. Intracranial injections of prolactin significantly increased the incidence of feeding behavior, parental feeding invitations, and crouching or sitting in the nest in food-deprived doves but not in freely fed animals. Empty crop sac weights of freely fed and food-deprived PRL-treated birds were not increased above control values, thus indicating that ICV PRL treatment did not result in significant stimulation of peripheral target organs. These results demonstrate a facilitative action of PRL on regurgitation-feeding responses and associated parental behaviors that is not restricted to squabs of one particular age range. They also indicate that PRL is capable of acting directly on the brain to promote these activities in the absence of PRL-induced changes in the crop sac and other peripheral target organs.
先前有报道称，对有过繁殖经验的非繁殖环鸽进行绵羊催乳素（PRL）的全身给药，可刺激其对7日龄寄养雏鸽产生亲代育雏行为。本实验的第一个部分重新检验了这一说法，实验对象为有经验的非繁殖鸟类，给它们不同年龄的测试雏鸽。每只视觉隔离的雄性和雌性鸽子每天接受两次皮下注射绵羊催乳素或赋形剂，持续7天，然后测试它们对一只1 - 3日龄、6 - 8日龄或11 - 13日龄寄养雏鸽的亲代反应。催乳素显著增加了在所有三个雏鸽年龄组测试中亲代反刍喂食事件的发生率或频率，此外，在对6 - 8日龄雏鸽的测试中，催乳素还增加了亲代喂食邀请（面向雏鸽的张嘴）的发生率。第二项研究探讨了在没有PRL诱导其他靶器官（如与嗉囊生长和扩张相关的器官）变化所产生的外周信号的情况下，PRL直接作用于中枢神经系统以促进亲代活动的程度。在这个实验中，使用6 - 8日龄的测试雏鸽来确定，每天两次脑室内（ICV）注射低于刺激外周靶器官所需剂量的PRL是否能增强亲代行为。注射时间表和行为测试程序与实验1中使用的相同。然而，在ICV注射PRL处理组和ICV注射赋形剂处理组中，各有一半的鸟类在测试前和测试期间禁食16小时，以控制PRL诱导的摄食过多和由此导致的嗉囊扩张，因为这可能会通过产生有利于反刍喂食行为表现的外周刺激而混淆实验结果。颅内注射催乳素显著增加了禁食鸽子的喂食行为、亲代喂食邀请以及蹲伏或坐在巢中的发生率，但在自由进食的动物中没有增加。自由进食和禁食的PRL处理组鸟类的空嗉囊重量没有超过对照组的值，因此表明ICV注射PRL处理并未导致外周靶器官的显著刺激。这些结果证明了PRL对反刍喂食反应和相关亲代行为的促进作用，这种作用并不局限于某一特定年龄范围的雏鸽。它们还表明，在没有PRL诱导嗉囊和其他外周靶器官变化的情况下，PRL能够直接作用于大脑以促进这些活动。
