Department of Physiology, School of Basic Medical Sciences, Harbin Medical University.
Department of Genetics, School of Basic Medical Sciences, Harbin Medical University.
ASN Neuro. 2020 Jan-Dec;12:1759091420944658. doi: 10.1177/1759091420944658.
Oxytocin, a hypothalamic neuropeptide essential for breastfeeding, is mainly produced in oxytocin neurons in the supraoptic nucleus (SON) and paraventricular nucleus. However, mechanisms underlying oxytocin secretion, specifically the involvement of hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) in oxytocin neuronal activity, remain unclear. Using a rat model of intermittent and continuous pup deprivation (PD) at the middle stage of lactation, we analyzed the contribution of HCN3 in oxytocin receptor (OTR)-associated signaling cascade to oxytocin neuronal activity in the SON. PD caused maternal depression, anxiety, milk shortage, involution of the mammary glands, and delays in uterine recovery, particularly in continuous PD. PD increased hypothalamic but not plasma oxytocin levels in enzyme-linked immunosorbent assay. In the SON, PD increased c-Fos expression but reduced expressions of cyclooxygenase-2 and HCN3 in Western blots and/or immunohistochemistry. Moreover, PD significantly increased the molecular association of OTR with HCN3 in coimmunoprecipitation. In brain slices, inhibition of HCN3 activity with DK-AH269 blocked prostaglandin E-evoked increase in the firing activity and burst discharge in oxytocin neurons in patch-clamp recordings. In addition, oxytocin-evoked increase in the molecular association between OTR and HCN3 in brain slices of the SON was blocked by pretreatment with indomethacin, an inhibitor of cyclooxygenase-2. These results indicate that normal activity of oxytocin neurons is under the regulation of an oxytocin receptor-cyclooxygenase-2-HCN3 pathway and that PD disrupts maternal behavior through increasing intranuclear oxytocin secretion in the SON but likely reducing bolus oxytocin release into the blood through inhibition of HCN3 activity.
催产素是一种下丘脑神经肽，对母乳喂养至关重要，主要由视上核（SON）和室旁核中的催产素神经元产生。然而，催产素分泌的机制，特别是超极化激活环核苷酸门控通道 3（HCN3）在催产素神经元活动中的作用，仍不清楚。本研究使用了一种在哺乳期中期间歇性和持续性剥夺幼仔（PD）的大鼠模型，分析了 HCN3 在催产素受体（OTR）相关信号级联中对 SON 中催产素神经元活动的贡献。PD 导致了母鼠的抑郁、焦虑、乳汁不足、乳腺萎缩和子宫恢复延迟，特别是在持续 PD 中。PD 增加了下丘脑但不是血浆中的催产素水平，通过酶联免疫吸附试验（ELISA）检测。在 SON 中，PD 增加了 c-Fos 的表达，但减少了 COX-2 和 HCN3 的表达，Western blot 和/或免疫组织化学检测。此外，PD 显著增加了 OTR 与 HCN3 在共免疫沉淀中的分子结合。在脑片上，用 DK-AH269 抑制 HCN3 活性阻断了前列腺素 E 诱发的催产素神经元放电活动和爆发性放电的增加，在膜片钳记录中。此外，在 SON 脑片中，用 COX-2 抑制剂吲哚美辛预处理阻断了催产素诱发的 OTR 和 HCN3 之间分子结合的增加。这些结果表明，催产素神经元的正常活动受到 OTR-COX-2-HCN3 途径的调节，PD 通过增加 SON 中的核内催产素分泌而破坏了母性行为，但可能通过抑制 HCN3 活性减少了催产素进入血液的爆发性释放。
