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Lesions of the medial preoptic area prevent the facilitation of maternal behavior produced by amygdala lesions.

In the present study we tested the hypothesis that the facilitation of maternal behavior produced by amygdala lesions is mediated through the medial preoptic area. Different groups of animals sustained lesions of the corticomedial amygdala (Group AM), the medial preoptic area (Group MPOA), both regions (Group AM-MPOA), the corticomedial amygdala and non MPOA control sites (Group AM-CX), and control sites (Groups LC or SC). Animals were tested for their maternal responses to foster pups presented daily for an 11 day period. It was found that groups sustaining lesions of the amygdala (Group AM and AM-CX) became maternal more rapidly than did Control Groups (LC and SC), Group MPOA, and Group AM-POA. However, animals in Group AM-POA were similar to Groups AM and AM-CX in that they did not avoid pups, whereas groups not sustaining lesions of the amygdala did. These results, taken together, suggest that amygdala-induced facilitation of maternal behavior in the nulliparous females is mediated through the MPOA. They suggest, moreover, the primary effect of removing the amygdala is to reduce avoidance of pups, with only secondary effects on maternal responsiveness.

Amygdala↗

The effects of paraventricular hypothalamic lesions on maternal behavior in rats.

The present study was undertaken to determine whether the disruptive effects of knife cuts which sever the lateral connections of the medial preoptic area (MPOA) on maternal behavior are mediated by interfering with the output of the paraventricular hypothalamic nucleus (PVN). Postpartum rats received one of the following: Knife cuts severing the lateral connections of the MPOA; knife cuts severing the lateral connections of the PVN; radiofrequency lesions of the PVN; sham lesions or knife cuts. Only females that received knife cuts severing the lateral connections of the MPOA showed severe deficits in maternal behavior. These results indicate that the influence of the MPOA on maternal behavior is not mediated by the output of the PVN. Since the PVN is the major source of oxytocin input to other brain regions, these results also suggest that oxytocinergic neural pathways are not critical for postpartum maternal behavior. Another important finding was that females with MPOA knife cuts that did not retrieve their young were capable of hoarding candy, suggesting that the retrieval deficit was not the result of a general oral motor deficit.

Animals↗

Nutritional status and behavior during lactation.

Effects of chronic maternal food restriction and time of day on maternal and pup behaviors were examined in ovariectomized Sprague-Dawley rats (n = 26). Dams were fed ad lib (AL) or were restricted to 85% (85 AL) or 70% (70 AL) of ad lib intake. Dams and their 5-pup litters were observed for 45 min at night on days 9, 14, and 19 of lactation and during the day on day 14. A novel behavioral instrument was used to observe maternal and pup behaviors. At night, food-restricted animals engaged in more nursing behaviors than AL animals. Differential pup stimuli may account for this difference. AL animals engaged in more nursing behaviors during the day than night, whereas 70 AL animals demonstrated the opposite diurnal pattern. Time of feeding may explain this difference. On the other hand, 85 AL animals behaved similarly during the day and at night. Therefore, alterations in circadian behavior patterns are less pronounced in rats mildly restricted (85 AL) than in rats more food restricted (70 AL).

Animals↗

Persistency of broodiness in recycled turkey hens.

Large White turkey breeder hens identified as broody during their initial egg production cycle were recycled into a second and third reproductive cycle in order to determine the persistency of broodiness. Egg production data included time to first egg, duration of lay and the number of eggs per hen. Nesting data included time to first broody nesting activity and duration of broody nesting activity. In general, there were no significant differences among the three cycles for the above observations. Mean values over the three cucles were as follows: 24.6 days to first egg following photostimulation; 49.4 days of egg production; 29.4 eggs per hen; 46.9 days from the first egg to first broody nesting and 59.7 days duration of nesting. Of 10 hens identified as broody in their first egg production cycle and followed through two additional 20-week cycles, seven hens demonstrated broody nesting behavior and nine had low rates of egg production. It was concluded that broody traits of a given hen are carried over into subsequent cycles.

Journal Article↗

Hormonal and behavioral aspects of maternal care in the hamster: a review.

This review covers a description of the maternal behavior cycle in the hamster and relationships between the endocrine system and prepartum changes in activity, aggression, sexual receptivity, and maternal care. Postpartum maternal behavior consists of the mother's "normal" cannibalism of some portion of her litter, the formation of a bond between mother and her young, the development of behavioral synchrony between the mother and her pups, and maternal aggression toward conspecifics. The maternal responses of virgin female, male, and juvenile animals are described and methodological considerations in the testing of both virgin and parturient animals are presented. Finally, a theoretical framework for considering the regulation of maternal care in the hamster is presented. Two main phases of regulation are proposed; an onset phase that that originates prepartum and depends on the physiological conditions of pregnancy and a maintenance phase which provides for the continuation of maternal care during lactation and is based on both endogenous maternal factors and external litter-related stimuli. A transition period beginning at parturition facilitates the shift between the onset and maintenance phases.

Aggression↗

Ontogenic variations in the content and distribution of progesterone receptor isoforms in the reproductive tract and brain of chicks.

Progesterone participates in the regulation of several functions in chicks such as ovulation, gonadal differentiation, and sexual and nesting behaviors. Many progesterone actions are mediated by specific intracellular receptors (PR) which are ligand-induced transactivators. Two PR isoforms that are functionally distinct in their ability to activate genes and regulate distinct physiological processes have been described in chicks: a full length form PR-B and the N-terminally truncated one PR-A which lacks the amino-terminal 128 amino acids of PR-B. PR isoforms have been detected in several tissues of both the adult and the embryo chick such as brain, ovary and oviduct. PR isoforms expression ratio varies among progesterone target tissues and under different hormonal and environmental conditions such as those presented during avian sexual maturity and the seasons of the year. These data let us to conclude that progesterone actions in brain, ovary, and oviduct highly depend on PR isoforms expression pattern and regulation.

Animals↗

Sexual selection: copycat mating in birds.

Female zebra finches may be influenced by the choices of other females when selecting mates, challenging the view that mate-choice copying should not occur in species with biparental care.

Animals↗

Non-destructive monitoring of trace element levels in short-tailed albatrosses (Phoebastria albatrus) and black-footed albatrosses (Phoebastria nigripes) from Torishima Island, Japan using eggs and blood.

Concentrations of 18 trace elements (V, Cr, Mn, Co, Cu, Zn, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, Hg, Tl and Pb) were determined in abandoned eggs of short-tailed albatrosses and abandoned eggs and blood of black-footed albatrosses from Torishima Island, Japan in 2002. Mercury concentration was highest among the toxic elements in egg content of both the two species. In some egg contents of black-footed albatrosses, Hg concentrations were higher than the threshold level that may cause decreased hatchability and aberrant nesting behavior in some avian species. Concentrations of Cd in egg content and Ba in egg content and shell increased with an increase in egg breadth/length ratio, whereas Hg in egg content showed an opposite trend in black-footed albatrosses. Since egg breadth/length ratio is known to increase with the age of mother bird, this result may imply that concentrations of these elements in eggs vary with age of mother bird. In blood of black-footed albatross chicks, concentration of Hg was highest among the toxic elements and the Hg concentration showed an increase in the later growth stages. In contrast, concentration of Sr in blood decreased with growth stage. Since the behaviour of Sr is similar to that of Ca in animals, it is conceivable that Sr was used along with Ca for the formation of bone.

Animals↗

The effects of early rearing environment on the hormonal induction of maternal behavior in virgin rats.

The present study investigated the effects of isolation rearing, through the artificial rearing paradigm (AR), on the hormonal induction of maternal behavior (MB) in female Sprague-Dawley rats. Between postnatal days (PND) 4 and 18, rat pups were raised either with their mothers (MR) or artificially, without their mothers (AR). As well, some of the AR pups were provided with additional maternal-like licking stimulation (AR-MAX) while the others were not given any additional stimulation (AR-MIN). At PND 60-100, AR (n = 28) and MR (n = 25) animals were ovariectomized (OVX). One week after the surgery, rats were either treated with a 2-week estrogen (E2) and progesterone (P) hormonal regimen or not treated with the hormone replacement. Maternal behavior testing with foster pups commenced 24 h following the removal of P treatment. Results demonstrated that MR animals showed increased pup licking and hover-crouching in comparison to AR animals and that hormonally primed groups became maternal more quickly than non-primed groups, regardless of the rearing history. There was also a significant interaction between the rearing condition (MR vs. AR) and hormonal treatment on the quality of maternal behavior exhibited. The highest level of licking and crouching was shown by the hormone-treated MR group. Mechanisms for these effects are discussed.

Animals↗