Lactation is indispensable for the pup's survival, but is considered a survival burden in dams under negative energy conditions. In the present study, we tested our hypothesis that oxytocin may facilitate energy investment to pups through behavioral control as well as milk ejection. Maternal care was observed in dams at 3 h but not 8 h after food deprivation. We investigated whether oxytocin in the dorsal raphe nucleus (DRN), which is involved in energy state-dependent regulation of maternal care, regulates maternal care. For this purpose, 2-pmol L368899, an oxytocin receptor antagonist, was injected into the DRN; after treatment, maternal care was inhibited in the dams with 3-h fasting, but not in the fed dams. In contrast, recovery of maternal care was observed in the dams with 8-h fasting who underwent 100-pmol oxytocin injection at the DRN. These results indicate that oxytocin in the DRN is required for displaying maternal behavior under fasting conditions, but not under fed conditions. Next, we investigated the site of oxytocin release. Presentation of pups decreased the oxytocin immunoreactivity at the paraventricular nucleus (PVN) of the hypothalamus in the 3-h-fasted dams, but not in the fed or 8-h-fasted dams. No change of the serum oxytocin level was observed. Few oxytocin-positive neurons projecting from the PVN to the DRN were detected through labeling with the retrograde tracer fluorogold. Oxytocin secreted at the PVN, which reaches the DRN, but not released as a hormone or neurotransmitter may mediate maternal care under food-restricted conditions.

泌乳对于幼仔的生存是必不可少的，但被认为是负能量条件下大坝的生存负担。在本研究中，我们检验了我们的假设，即催产素可以通过行为控制以及排乳来促进幼犬的能量投资。在食物被剥夺后的3 h而非8 h的大坝中观察到产妇护理。我们调查了背沟核（DRN）中的催产素是否参与了对孕产妇保健的能量状态依赖性调节，从而调节了孕产妇保健。为此，将2-pmol催产素受体拮抗剂L368899注入DRN。经过治疗后，禁食3小时后母坝中的产妇护理受到抑制，但喂食的母坝中母体护理受到抑制。相比之下，禁食8小时并在DRN接受100 pmol催产素注射的大坝中观察到了产妇护理的恢复。这些结果表明，DRN中的催产素是在禁食条件下（而非在进食条件下）表现出孕产妇行为所必需的。接下来，我们研究了催产素释放的部位。在3小时禁食的大坝中，幼崽的出现降低了下丘脑室旁核的催产素免疫反应性，但在喂食或8小时禁食的大坝中却没有。没有观察到血清催产素水平的变化。通过用逆行示踪剂荧光金标记，从PVN投射到DRN的催产素阳性神经元很少。PVN分泌的催产素到达DRN，但未以激素或神经递质的形式释放，可能会在食物限制的情况下调解孕产妇保健。但不在喂食条件下。接下来，我们研究了催产素释放的部位。在3小时禁食的大坝中，幼崽的出现降低了下丘脑室旁核的催产素免疫反应性，但在喂食或8小时禁食的大坝中却没有。没有观察到血清催产素水平的变化。通过用逆行示踪剂荧光金标记，从PVN投射到DRN的催产素阳性神经元很少。PVN分泌的催产素到达DRN，但未以激素或神经递质的形式释放，可能会在食物限制的情况下调解孕产妇保健。但不在喂食条件下。接下来，我们研究了催产素释放的部位。在3小时禁食的大坝中，幼崽的出现降低了下丘脑室旁核的催产素免疫反应性，但在喂食或8小时禁食的大坝中却没有。没有观察到血清催产素水平的变化。通过用逆行示踪剂荧光金标记，从PVN投射到DRN的催产素阳性神经元很少。PVN分泌的催产素到达DRN，但未以激素或神经递质的形式释放，可能会在食物限制的情况下调解孕产妇保健。但不在喂食或8小时禁食的水坝中。没有观察到血清催产素水平的变化。通过用逆行示踪剂荧光金标记，从PVN投射到DRN的催产素阳性神经元很少。PVN分泌的催产素到达DRN，但未以激素或神经递质的形式释放，可能会在食物限制的情况下调解孕产妇保健。但不在喂食或8小时禁食的水坝中。没有观察到血清催产素水平的变化。通过用逆行示踪剂荧光金标记，从PVN投射到DRN的催产素阳性神经元很少。PVN分泌的催产素到达DRN，但未以激素或神经递质的形式释放，可能会在食物限制的情况下调解孕产妇保健。