Abstract
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•Pre-labor cesarean delivery (CD) often causes postpartum depression and hypogalactia.•These effects are associated with abnormal activation of oxytocin neurons.•Over-excitation of oxytocin neurons inhibits oxytocin release from axon terminals.•Intranasal oxytocin can restore CD-disrupted maternal behavior and oxytocin neuronal activity.
Oxytocin (OT) is a key factor for maternal behavior. However, neurochemical regulation of OT neurons, the major source of OT, remains incompletely understood. Here we report the effect of intranasally-applied OT (IAO) on OT neuronal activity in the supraoptic nucleus (SON) and on maternal behavior in a rat model of cesarean delivery (CD) at day 4–5 (stage I) and day 8–9 (stage II) following delivery. We found that at stage I, CD dams exhibited significantly longer latency of pup retrieval, lower number of anogenital licks and smaller acinar area of the mammary glands. In the SON, the number of OT neurons expressing phosphorylated extracellular signal-regulated protein kinase 1/2 (pERK 1/2) decreased significantly. IAO reversed the depressive-like maternal behavior and involution-like change in the mammary glands, and restored the number of pERK1/2-positive OT neurons in CD dams. At stage II, CD did not significantly influence the latency of retrieval and pERK1/2 expression in the SON. However, CD still reduced the number of anogenital licks during suckling, which was reversed by IAO. Notably, IAO but not hypodermic OT application in CD dams significantly increased litter’s body weight gains. In brain slices, CD but not CD plus IAO significantly depolarized membrane potential and increased spike duration in OT neurons. In vasopressin neurons, CD, but not CD plus IAO, significantly depolarized membrane potential and increased the firing rate. Thus, decreased OT neuronal activity and increased vasopressin neuronal activity impair maternal behavior in CD dams, which can be prevented by IAO .