Differences in the endocrine and behavioral profiles during the peripartum period in macaques

The marmoset as a model for the study of primate parental behavior

Parental behavior is important for the development of mammalian offspring. Research on the mechanisms underlying parental behavior, however, has been largely restricted to rodent models. As a consequence, although research on parent-infant relationships has been conducted using macaque monkeys for more than half a century, little is known about the neural mechanisms and brain regions associated with such behaviors in primates. This article reviews parental behavior and its endocrinological mechanisms in marmosets and tamarins, both cooperative breeders in the callitrichid family, and compares these findings with studies of macaque monkeys. The paper examines the similarities and differences between marmosets and humans, and suggests the possibility that marmosets can be a model for future studies of the neural underpinnings and endocrinology underlying human parental behavior.

Mother-infant interactions in free-ranging rhesus macaques: relationships between physiological and behavioral variables

Studies of mother-infant relationships in nonhuman primates have increasingly attempted to understand the neuroendocrine bases of interindividual variation in mothering styles and the mechanisms through which early exposure to variable mothering styles affects infant behavioral development. In this study of free-ranging rhesus macaques on Cayo Santiago, Puerto Rico, we aimed to: 1) compare lactating and nonlactating females to investigate whether lactation is associated with changes in plasma cortisol, prolactin and oxytocin, as well as changes in CSF levels of serotonin and dopamine metabolites (5-HIAA and HVA); 2) examine the extent to which interindividual variation in maternal physiology is associated with variation in maternal behavior; 3) examine the extent to which interindividual variation in infant physiology and behavior is accounted for by variation in maternal physiology and behavior. Lactating females had higher plasma concentrations of cortisol, prolactin, and oxytocin but lower CSF concentrations of HVA than nonlactating females. Variation in maternal rejection behavior was positively correlated with variation in maternal plasma cortisol levels and in CSF 5-HIAA levels while variation in the time spent nursing and grooming was associated with maternal plasma oxytocin levels. Infants who were protected more by their mothers had higher cortisol levels than those who were protected less, while infants who were rejected more had lower CSF 5-HIAA than infants who were rejected less. Since exposure to high levels of maternal protectiveness and rejection is known to affect the offspring's behavior and responsiveness to the environment later in life, our results are consistent with the hypothesis that these effects are mediated by long-term changes in the activity of the offspring's HPA axis and brain serotonergic system.

Ultrasonic vocalizations emitted during dyadic interactions in female mice: a possible index of sociability?

Despite the evidence that ultrasonic vocalizations are a consistent component of the behavioural repertoire of female mice, only few studies have investigated this phenomenon. In this paper, we reported new data about ultrasonic vocalisations emitted during female-female mice social encounters. In particular, we first showed that the resident female utters a considerable number of 70 kHz calls and that the number of calls seems to be modulated by the motivational state of the emitter during the estrous cycle: sexually receptive females emitted fewer ultrasonic vocalizations than non-receptive ones in the presence of a female intruder. A strong positive correlation linked the number of calls and the time spent by the resident sniffing the intruder female. Moreover, the number of calls uttered during interaction with an unknown female partner significantly decreased with pregnancy and ageing. Secondly we reported that 1-year-old female mice showed a reduction of ultrasonic calls in the presence of a partner they had been exposed to, only if the re-exposure (test) occurred 30 min after the previous presentation. If the test was performed with a delay of 60 min, the number of calls emitted did not decrease. These results confirm that ultrasonic vocalizations emitted during social interaction with a female conspecific can be used as an index of social recognition and can be useful to detect age-related disruption of social memory in female mice.