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 E₂-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.

催产素是母乳喂养必不可少的下丘脑神经肽，主要由视上核 (SON) 和室旁核的催产素神经元产生。然而，催产素分泌的潜在机制，特别是超极化激活的环核苷酸门控通道 3 (HCN3) 参与催产素神经元活动，仍不清楚。我们在哺乳中期使用间歇和连续幼崽剥夺 (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 会导致产妇抑郁、焦虑、乳汁短缺、乳腺退化和子宫恢复延迟，尤其是在持续 PD 中。在酶联免疫吸附试验中，PD 增加了下丘脑但不增加血浆催产素水平。在 SON 中，PD 增加了 c-Fos 表达，但在蛋白质印迹和/或免疫组织化学中降低了环氧合酶-2 和 HCN3 的表达。此外，PD 显着增加了 OTR 与 HCN3 在共免疫沉淀中的分子关联。在脑切片中，用 DK-AH269 抑制 HCN3 活性可阻断前列腺素 E_{2 -}在膜片钳记录中诱发催产素神经元放电活动和爆发放电的增加。此外，催产素诱发的 SON 脑切片中 OTR 和 HCN3 之间分子关联的增加被吲哚美辛（环加氧酶 2 的抑制剂）预处理所阻断。这些结果表明，催产素神经元的正常活动受催产素受体-环氧合酶-2-HCN3 通路的调节，并且 PD 通过增加 SON 核内催产素的分泌来扰乱母体行为，但可能通过抑制HCN3 活性。