Reorganization of perineuronal nets in the medial Preoptic Area during the reproductive cycle in female rats.

Perineuronal nets (PNNs) are aggregations of extracellular matrix associated with specific neuronal populations in the central nervous system, suggested to play key roles in neural development, synaptogenesis and experience-dependent synaptic plasticity. Pregnancy and lactation are characterized by a dramatic increase in neuroplasticity. However, dynamic changes in the extracellular matrix associated with maternal circuits have been mostly overlooked. We analyzed the structure of PNNs in an essential nucleus of the maternal circuit, the medial preoptic area (mPOA), during the reproductive cycle of rats, using the Wisteria floribunda (WFA) label. PNNs associated to neurons in the mPOA start to assemble halfway through gestation and become highly organized prior to parturition, fading through the postpartum period. This high expression of PNNs during pregnancy appears to be mediated by the influence of estrogen, progesterone and prolactin, since a hormonal simulated-gestation treatment induced the expression of PNNs in ovariectomized females. We found that PNNs associated neurons in the mPOA express estrogen receptor α and progesterone receptors, supporting a putative role of reproductive hormones in the signaling mechanisms that trigger the assembly of PNNs in the mPOA. This is the first report of PNNs presence and remodeling in mPOA during adulthood induced by physiological variables.

Raising overlapping litters: Differential activation of rat maternal neural circuitry after interacting with newborn or juvenile pups.

The maternal behaviour of a rat dynamically changes during the postpartum period, adjusting to the characteristics and physiological needs of the pups. This adaptation has been attributed to functional modifications in the maternal circuitry. Maternal behaviour can also flexibly adapt according to different litter compositions. Thus, mothers with two overlapping litters can concurrently take care of neonate and juvenile pups, mostly directing their attention to the newborns. We hypothesised that the maternal circuitry of these mothers would show a differential activation pattern after interacting with pups depending on the developmental stage of their offspring. Thus, we evaluated the activation of several areas of the maternal circuitry in mothers of overlapping litters, using c-Fos immunoreactivity as a marker of neuronal activation, after interacting with newborns or juveniles. The results showed that mothers with overlapping litters display different behavioural responses towards their newborn and their juvenile pups. Interestingly, these behavioural displays co-occurred with specific patterns of activation of the maternal neural circuitry. Thus, a similar expression of c-Fos was observed in some key brain areas of mothers that interacted with newborns or juveniles, such as the medial preoptic area and the nucleus accumbens, whereas a differential activation was quantified in the ventral region of the bed nucleus of the stria terminalis, the infralimbic and prelimbic subregions of the medial prefrontal cortex and the basolateral and medial nuclei of the amygdala. We posit that the specific profile of activation of the neural circuitry controlling maternal behaviour in mothers with overlapping litters enables dams to respond adequately to the newborn and the juvenile pups.

Incentive value of newborn pups relative to juveniles for mother rats raising overlapping litters.

In rats, successful mating during the postpartum estrus results in the temporal overlapping of successive litters within the maternal nest. Mothers with two overlapping-litters (OLM) simultaneously take care of neonate and juvenile pups; however, they mostly direct their attention to the neonates. We hypothesized that these differences reflect an adaptation to the specific characteristics and needs of the two litters and not a lack of interest in the juveniles. To test this hypothesis, we assessed the relative incentive value of newborns and juveniles for OLM in a preference test and compared it with that exhibited by mothers in early (EPM) and late (LPM) postpartum, which were raising only newborns or only juveniles, respectively. Results showed that OLM spent similar time in the newborns and juveniles compartments and did not prefer the newborns as did the EPM, however, similarly to them, OLM made more attempts to get access to the newborns than the juveniles. On the other hand, OLM and LPM did not exhibit a clear preference between the stimuli. These results indicate that both neonates and juveniles have incentive value for OLM, although these mothers invest more effort in the newborns. These results point out to a unique behavioral profile of OLM, which shows similarities with EPM and LPM on different behavioral measures. They also support the idea that motivational processes underlying maternal behavior are complex and dynamic, adapting the response of the mother to pups' needs and the context.

Estado emocional y auto-percepción maternal de mujeres presas con sus hijos en Uruguay / Emotional state and maternal self-perception of imprisoned mothers together with their children in Uruguay / Estat emocional i autopercepció maternal de dones preses amb fills a l’Uruguai

Este estudio tuvo como objetivos describir algunos aspectos sociodemográficos de 17 mujeres que convivían con sus hijos en la cárcel en Montevideo y comparar sus niveles de sintomatología ansiosa y depresiva, así como la percepción de su maternidad, entre aquellas que informaron haber padecido abuso sexual en la infancia y/o en la adolescencia (el 41 %) y las que no lo hicieron. Los niveles de ansiedad de rasgo y de sintomatología depresiva fueron significativamente mayores en las primeras. Ninguno de los indicadores asociados con la percepción de actitudes maternales difirió entre ambos grupos. Estos resultados sugieren que el abuso sexual influye de forma negativa en el estado emocional de las madres sin afectar la percepción de su maternidad

This study aimed to describe the socio-demographic characteristics of 17 women incarcerated with their children in Montevideo and to compare their levels of anxiety, the depressive symptoms and their perception of mothering, among those who reported sexual abuse during their childhood and/or adolescence and those who didn't. Forty one percent of the mothers reported sexual abuse during childhood and/or adolescence showing significantly higher levels of depressive and anxiety symptoms, compared to those who did not report any kind of abuse. The perception of motherhood did not differ between the groups. This study shows that the early experiences of sexual abuse increase anxiety and depressive symptoms without affecting the perception of mothering in imprisoned women with children

Aquest estudi té com a ob­jectius descriure alguns aspectes socio-demográfics de 17 dones que convivien amb els seus fills a la presó a Montevideo I comparar els seus nivells de simptomatologia ansiosa I depressiva, així com la percepció de la seva maternitat, entre aquelles que van informar haver patit abús sexual a la infantesa i/o adolescència (el 41 %) I les que no ho van fer. Els nivells d'ansietat de tret I de simptomatologia depressiva van ser significativament més grans en les primeres. Cap dels indicadors associats amb la percepció d'actituds maternals va diferir entre els dos grups. Aquests resultats suggereixen que l'abús sexual influeix de manera negativa en l'estat emocional de les mares sense afectar la percepció de la seva maternitat

Dopaminergic activity mediates pups' over male preference of postpartum estrous rats.

Pups have greater incentive value than males for rats during the postpartum estrus (PPE); a period when females are both maternally and sexually motivated. Mesolimbic dopaminergic system has been proposed as a general motivational circuit; however in the literature it has been more related to the control of the motivational aspects of maternal than sexual motivation of females. Therefore, we aimed to assess the effect of antagonizing dopaminergic neurotransmission of PPE females on their preference for pups over a male. To achieve this objective we tested PPE rats in a Y-maze with three-choice chambers (one containing eight pups, the other a male and the last one no stimulus) after the systemic administration of the dopaminergic antagonist haloperidol (0.0; 0.025 or 0.05 mg/kg). Furthermore, to determine if this dopaminergic antagonist differentially affects maternal and sexual motivations when pups and male are not competing, we evaluated the effect of haloperidol in the preference of females for pups vs. a non-receptive female and for a male vs. a non-receptive female. In the preference test for pups vs. male, both doses of haloperidol decreased the time that females spent in pups' chamber while increased the time that they spent in male's chamber, resulting in a lack of preference between both incentives. Besides, haloperidol reduced the effort -attempts to get access to the stimuli- made by the females to obtain the pups. Conversely, 0.05 mg/kg of haloperidol did not affect the preference for both incentives when they were confronted to a non-receptive female. Together, these results indicate that the dopaminergic activity mediates pups' preference over male during the PPE and point toward a more relevant role of this system in females' behavioral output when incentives are competing.

Previous and recent maternal experiences modulate pups' incentive value relative to a male without affecting maternal behavior in postpartum estrous rats.

This study extends the behavioral analysis of the postpartum estrus (PPE) which represents a unique period in the female rat's lifetime when maternal and sexual motivations co-exist. The aim of this study was to explore how previous and recent maternal experiences influence the maternal responses to pups when confronted with a male in a preference test or when they are presented independently in the home cage. To achieve this objective, we firstly compared the maternal behavior in the home cage and the preference for pups or a male in a Y-maze of primiparous and multiparous females approximately twelve hours after delivery. No differences were observed in the active and passive components of the maternal behavior of primiparous and multiparous rats; however second-time mothers made more efforts to gain access to the pups and tended to spend more time with them in the Y-maze than maternally inexperienced dams. In a second experiment, we assessed the influence of recent maternal experience with pups on PPE females' behavior by comparing pups vs. male preference and maternal behavior of females that had experienced continuous or limited (approximately two hours) interaction with their litters after parturition was completed. PPE rats subjected to reduced interaction with their pups preferred the male, while females continuously exposed to pups chose them over the male. This change in females' preference was not accompanied by significant alterations of maternal performance in the home cage, although anogenital licking tended to decrease in females with limited mother-litter interaction. Together, the results of these experiments indicate that previous and recent maternal experiences influence the motivational responses of PPE females, and that these effects are more evident when both motivations compete.

Maternal and affective behaviors of lactating rats reared in overlapping litters.

Postpartum mating in rats gives rise to complex family units consisting of the mother and two overlapping litters. As a consequence, newborn pups of the second litter, since the moment they are born, acquire experience not only from interaction with the mother and age-matched littermates but also from interaction with older siblings. Newborn pups reared in overlapping litters (OLs) receive a different pattern of maternal stimulation compared to those reared in single litters (SL: one litter of same aged pups), as the mothers reduce some maternal behavior components and juvenile pups from the first litter develop maternal behavior. Since there is strong evidence showing that variations in maternal behavior are transmitted throughout generations, we hypothesized that the altered pattern of maternal stimulation received by OL reared females would modify their behavior during motherhood. To test this hypothesis maternal behavior, maternal aggression and experimental anxiety of dams reared under OL and SL conditions during the first postpartum week were compared. No differences were found between the groups in their maternal behavior and aggression. This result may be explained by the maternal behavior of the juveniles that could compensate for the deficits in the caregiving behaviors received by OL litters. However, a subtle temporal reorganization of the licking behavior was found in OL reared mothers, together with an increased anxiety-related behavior in the plus maze test. These results suggest dissociation in the effects provoked by early environmental alterations on different behavioral systems, and more importantly, that independently of their early family composition, both groups can cope effectively with the changing demands of the pups.

Coexpression of sexual behavior and maternal aggression: the ambivalence of sexually active mother rats toward male intruders.

The sexually active female rat solicits the male to approach for copulation, while the maternal dam displays aggression to expel him from the nest, suggesting that both behaviors are mutually exclusive. However, the rat has a postpartum estrus during which she is sexual and maternally motivated. Can she perceive the male as attractive and aversive, soliciting and attacking him at the same time? This study shows that postpartum estrous females exhibit a merge of sexual and maternal aggressive responses toward male intruders in the home cage. The concurrent expression of these behaviors did not affect their intensities, although the stimulation of maternal behavior increased maternal aggression without modifying sexual solicitation. These results indicate that the postpartum estrous rat can optimally express two opposite and independently regulated motivations, and that the male can be perceived as an ambivalent stimulus.