The changing role of the medial preoptic area in the regulation of maternal behavior across the postpartum period: Facilitation followed by inhibition
Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, 197 University Avenue, Newark Campus, NJ 07102, USA Behavioural brain research
(Impact Factor: 3.03).
12/2009; 205(1):238-248. DOI: 10.1016/j.bbr.2009.06.026
Maternal behavior in rats undergoes considerable plasticity in parallel to the developmental stage of the pups, resulting in distinct patterns of maternal behavior and care at different postpartum time points. The medial preoptic area (mPOA) of the hypothalamus is one critical neural substrate underlying the onset and early expression of maternal behavior in rats but little is known about its specific functional role in the evolving expression of maternal behavior across the postpartum period. The present study uses a reversible local neural inactivation method to examine the role of the mPOA in the regulation of maternal behavior throughout the postpartum period, particularly extending into the late postpartum, a little examined period. This approach avoids the compensatory plasticity in CNS that occurs after permanent lesions, and allows the repeated testing of same individuals. Early (PPD7–8) and late (PPD13–14) postpartum maternal behavior was evaluated in female rats following infusions of bupivacaine or vehicle into the mPOA or into control areas. As expected, mPOA inactivation severely but transiently disrupted early postpartum maternal behavior whereas infusion of vehicle or inactivation of adjacent control sites did not. Later in the postpartum period, however, transient mPOA inactivation facilitated the expression of maternal behaviors, highly contrasting the behavioral expression levels characteristic of late postpartum. Results strongly demonstrate that the mPOA is differentially engaged throughout postpartum in orchestrating appropriate maternal responses with the developmental stage of the pups.
Available from: Josephine M Johns
- "Additionally, dam preference-like behavior and relationship with oxytocin (OT) expression in the medial preoptic area (MPOA) was explored, as OT has been shown to play an essential role in onset and maintenance of early maternal behavior in both human   and rodent models   . Additionally, OT dynamics has been shown to be altered in rat dams gestationally-exposed to cocaine   , including decreased expression in the MPOA  , a region consistently shown to be critical for maternal behavior     . However, the mechanisms underlying these relationships are still unclear with studies suggesting cocaine can directly alter OT dynamics    and recent studies suggesting maternal–infant interactions may regulate OT dynamics across the postpartum period [3,42–44]. "
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ABSTRACT: Cross-fostering studies suggest cocaine-induced deficits in maternal behavior could be associated with altered behavior of offspring following prenatal cocaine-exposure. Neonatal vocalizations are an important offspring cue facilitating early interactions between dam and rodent pup offspring and have been shown to be altered following prenatal cocaine-exposure. It is unclear how variations in acoustic parameters of USVs impact maternal behavior and the mechanism(s) underlying these processes. The present study examined differences in cocaine-exposed and control rodent dam maternal preference of cocaine-exposed or untreated pups in a dual choice apparatus. Relationship of preference-like behavior with pup USVs and dam oxytocin expression was explored. Gestational cocaine-exposure interfered with preference-like behavior of dams on postpartum day 1 with cocaine-exposure associated with decreased time spent on the cocaine-exposed pup side compared to the control pup side, and decreases in preference-like behavior associated in part with decreased number of USVs being emitted by cocaine-exposed pups. On postpartum day 5, decreased oxytocin expression in the medial preoptic area was associated with altered preference-like behavior in cocaine-exposed dams, including frequency and latency to touch/sniff pups. Results indicate cocaine's effects on the mother-infant relationship is likely synergistic, in that cocaine influences mother and offspring both independently and concertedly and that variations within pup vocalizations and the oxytocin system may be potential mechanism(s) underlying this synergistic relationship during the postpartum period.
Available from: Anna Robak
- "Moreover, it has been shown that Gal takes part in regulation of reproduction (Splett et al., 2003; Pandit and Saxena, 2010) at the pre-optic area (POA) level. POA is a sexually dimorphic brain region (Bogus-Nowakowska et al., 2010), and it is involved in control over the neuroendocrine and behavioural context of reproduction by regulating release of pituitary gonadotrophins and parental behaviour (Merchenthaler et al., 1990; Pereira and Morrell, 2009). Some Gal containing cells in the medial pre-optic area colocalize with oestrogen (Bloch et al., 1992), what suggests that the interaction between Gal and steroid hormones occurring in the medial pre-optic area may be important for regulation of reproductive functions (Bloch et al., 1992). "
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ABSTRACT: This study describes the distribution of galanin (Gal) and galanin receptor 2 (GalR2) in the pre-optic area (POA) of the female guinea pig. Frozen sections were undergone for a routine immunofluorescence labelling. Gal and GalR2 display immunoreactivity in all parts of the pre-optic area. Gal shows reactivity both in perikarya and fibres, whereas GalR2 was observed only in perikarya. Gal- and GalR2-immunoreactive (-ir) perikarya were the most numerous in the medial pre-optic area (MPA) with the highest reactivity in its dorsal part. In the median pre-optic nucleus (MPN) and periventricular pre-optic nucleus (PPN), only single Gal- and GalR2-ir neurons were observed. The highest density of Gal-ir fibres was revealed in the PPN and the lowest in the lateral pre-optic area (LPA). The results of this study indicate that the distribution pattern of Gal containing neurons overlaps well with the distribution pattern of GalR2-positive neurons, especially in the MPA. This may suggest GalR2-dependent activity in this brain region.
- "Recent research has revealed that the mPOA is differentially engaged throughout the postpartum period to orchestrate maternal responses to the changing needs of the developing pups, from a necessary facilitatory role during early postpartum period to an inhibitory role during late postpartum period . Viewed together, we propose that elevated MCH in the postpartum mPOA toward the end of lactation is one mechanism contributing to the changing role of the mPOA in maternal responsiveness across the postpartum period. "
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ABSTRACT: Melanin-concentrating hormone (MCH) is an inhibitory neuropeptide mainly synthesized in neurons of the lateral hypothalamus and incerto-hypothalamic area of mammals that has been implicated in behavioral functions related to motivation. During lactation, this neuropeptide is also expressed in the medial preoptic area (mPOA), a key region of the maternal behavior circuitry. Notably, whereas MCH expression in the mPOA progressively increases during lactation, maternal behavior naturally declines, suggesting that elevated MCHergic activity in the mPOA inhibit maternal behavior in the late postpartum period. To explore this idea, we assessed the maternal behavior of early postpartum females following bilateral microinfusions of either MCH (50 and 100ng/0.2μl/side) or the same volume of vehicle into the mPOA. As expected, females receiving 100ng MCH into the mPOA exhibited significant deficits in the active components of maternal behavior, including retrieving and nest building. In contrast, nursing, as well as other behaviors, including locomotor activity, exploration, and anxiety-like behavior, were not affected by intra-mPOA MCH infusion. The present results, together with previous findings showing elevated expression of this neuropeptide towards the end of the postpartum period, suggest that modulation of mPOA function by MCH may contribute to the weaning of maternal responsiveness characteristic of the late postpartum period.
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