Involvement of Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 3 in Oxytocin Neuronal Activity in Lactating Rats With Pup Deprivation

Abstract

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.

Cardiovascular protective properties of oxytocin against COVID-19

“…Interestingly, in rat dams separated from her pups, hypothalamic OXT secretion increased; however, plasma OXT levels were low. This is due to that over-activation of OTR signaling causes post-excitation inhibition and a subsequent reduction of the secretory activity of OXT neurons [ 130 , 139 ]. Thus, it is possible that over-expression or over-activation of OTR exerts an effect opposite to the physiological effect although normal OTR signaling is essential for CV protection.…”

Oxytocin Modulation of Maternal Behavior and Its Association With Immunological Activity in Rats With Cesarean Delivery

“…Analyses of behaviors, Western blots, imaging and patchclamp recordings have been described in previous reports (D. Li et al, 2020). In immunohistochemistry, the number of c-Fos-positive cells and OT neurons was counted only in the SON somatic area excluding the ventral glial lamina wherein astrocytic somata are located.…”

“…Maternal behavior in mammals manifests as maternal care of the offspring and suckling (P erez-Torrero and Rubio-Navarro, 2015). The delayed suckling, reduced anogenital licking in CD dams and poor dams' body weight gain indicate the occurrence of depressive-like maternal behavior as shown in rat dams separated from their newborns (Liu et al, 2019;D. Li et al, 2020D.…”

“…The supernatant was then frozen until assay. The assay was performed using kits from ImmunoClone (product of I&C, USA and distributed by YBio, Shanghai, China) including a general OT assay kit (IC-OT-Ge) and a rat CRH assay kit (IC-CRH-Ra) as instructed by the manual, which is similar to our previous publication (D. Li et al, 2020). The minimum detectable limit was 5.8 pg/mL for OT and 4.58 pg/ mL for CRH, respectively.…”

“…However, interactions between OT and immune system as well as their influence on maternal behavior during lactation remain poorly understood. For example, persistent social stress causes OT increase in the hypothalamus but disrupts normal maternal behavior and lactation (D. Li et al, 2020Li et al, , 2021. The responses of HPA axis to various stresses are reduced markedly during lactation (Smotherman et al, 1976) and OT levels are negatively correlated with the symptom of postpartum depression among women (Thul et al, 2020).…”