Inhibition of post-partum maternal behaviour in the rat by injecting an oxytocin antagonist into the cerebral ventricles

Abstract

Endogenous oxytocin released into the brain at parturition may stimulate the onset of maternal behaviour. In this study an attempt was made to block spontaneous maternal behaviour following natural delivery in Wistar rats by the injection of an antagonist of oxytocin into the cerebral ventricles. The analogue antagonist, d(CH2)5-8-ornithine-vasotocin, was administered by injection into a chronically implanted cannula in the right lateral ventricle at hourly intervals, beginning immediately after the expulsion of the first pup. The antagonist did not interfere with the normal progress of parturition or birth-related behaviours. After delivery of the last pup, mothers rested for 40 min in the test cage with the pups having been removed. Four pups and standard nesting material were then presented. Latency to pup carrying and duration of pup manipulation, nest building, and time spent on the nest with the pups, as well as duration of autogrooming and general activity were determined. Saline-injected controls started gathering the pups immediately and usually showed all elements of maternal behaviour within 10 min. Antagonist-treated mothers showed a marked delay in the onset of pup grouping and other maternal behaviours. At the end of 1 h, two out of six mothers had not yet picked up a single infant. Pups left overnight with their mothers were gathered into the nest and suckled, and no long-term effects of the antagonist were evident on retesting. The effectiveness of oxytocin antagonist in suppressing the rapid onset of post-partum maternal behaviour supports the hypothesis that centrally released oxytocin is involved in this process.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional Magnetic Resonance Imaging Shows Oxytocin Activates Brain Regions Associated with Mother–Pup Bonding during Suckling

“…In the rat, destruction of the PVN delays the onset of maternal behaviors (Insel and Harbaugh, 1989). Similar effects have been observed by administering OTA (van Leengoed et al, 1987). Our present data provide evidence that oxytocin continues to be released within this area in fully maternal postpartum rats.…”

“…The release of oxytocin in the CNS during parturition initiates the onset of maternal behaviors. Expression of maternal behaviors in sheep and rats is delayed after blockade of oxytocin receptors during parturition (van Leengoed et al, 1987;Levy et al, 1992). Oxytocin release in response to suckling has been measured using microdialysis in the substantia nigra, olfactory bulbs, mediobasal hypothalamus, bed nucleus of the stria terminalis, medial preoptic area (MPOA), and septum of parturient sheep (Kendrick et al, 1997), as well as in sites of origin, the PVN and SON (Neumann et al, 1993a,b).…”

C-tactile afferents: Cutaneous mediators of oxytocin release during affiliative tactile interactions?

“…Such changes appear to facilitate the formation of maternal motivations and infant recognition (Keverne and Curley, 2004). The first demonstration that oxytocin is critical for the expression of maternal behaviour came from studies showing that intracerebroventricualr (ICV) infusions of oxytocin induce maternal behaviours in virgin female rats (Pedersen and Prange, 1979), while in contrast ICV infusions of an oxytocin receptor antagonist delay this onset (van Leengoed, et al, 1987). In sheep too, ICV infusions of oxytocin were reported to induce rapid onset of full maternal responsivity in non-pregnant ewes as long as they were primed with oestrogen (Kendrick et al, 1997).…”

Impact of gestational cocaine treatment or prenatal cocaine exposure on early postpartum oxytocin mRNA levels and receptor binding in the rat

“…The focus of this paper was on the biological oxytocin response to pups and not the measurement of maternal behavior, other than the general maternal response. Thus, litters were culled to four pups following delivery (two male and two female) to ensure maternal stimulation, since litters of this size have been shown to elicit maternal care and oxytocin response (Van Leengoed et al, 1987).…”

“…The onset of maternal behavior is thought to stem primarily from hormonal changes that occur at parturition (Insel and Harbaugh, 1989;Numan and Insel, 2003;Van Leengoed et al, 1987), while the maintenance of established maternal behavior appears to be less hormonedependent. The onset of maternal behavior is characterized by a dramatic drop in progesterone levels accompanied by a rise in estrogen, which remains elevated through much of the postpartum period (Terkel and Rosenblatt, 1968;Terkel and Rosenblatt, 1972).…”