Effects of neonatal novelty exposure on sexual behavior, fear, and stress‐response in adult rats

Abstract

Environmental stimuli in early life may result in permanent behavioral and physiological changes. Present study evaluated the effects of exposing pups to a novel environment on behaviors (open-field test and sexual behavior) and prolactin stress-responses in adult male rats. Half of a litter was daily removed outside (OUT) from the nest and stimulated by handling for 3 min, while the other half remained inside (IN) the nest and was also handled for the same period during the first 10 days postpartum. Maternal behavior after all the pups were returned to the nest was not different between IN and OUT littermates. In adulthood, OUT males showed increased general and central locomotion activity in the open-field test, reduced sexual behavior, and attenuated prolactin secretion in response to restraint stress compared with the IN littermates. The repeated exposition of rat pups to a novel environment is a causal factor for the long-lasting behavioral and endocrine changes. The premature exposition of the pup to unfamiliar environments decreases fear and stress-response, and also reduces sexual behavior. We suggest that the absence of the odor of the mother may be crucial to explain the effects detected in adulthood.

Neonatal Novelty-Induced Persistent Enhancement in Offspring Spatial Memory and the Modulatory Role of Maternal Self-Stress Regulation

“…While higher quantity of maternal care has been shown to be associated with increased GR expression (Liu et al, 1997;Francis et al, 1999), here it is unlikely that the memory enhancement induced by novelty exposure is due solely to a greater amount of maternal care, because dams, whether high or low caregivers, did not show preferential care toward the novelty-exposed pups (Tang et al, 2006;Benetti et al, 2007). It is possible, and remains to be determined, whether the previously reported association between quantity of maternal care and offspring GR expression may be due to differences in dams' circulating corticosterone level, as manipulation of dams' circulating corticosterone is known to result in changes in the offspring's HPA function and spatial memory, likely through the mother's milk (Catalani et al, 1993(Catalani et al, , 2000(Catalani et al, , 2010.…”

“…However, there have been recent findings suggesting that maternal care alone is neither sufficient nor necessary for the production of stimulation-induced effects (Denenberg, 1999;Pryce and Feldon, 2003;Macrì and Würbel, 2006;Parker et al, 2006;Tang et al, 2006) and that other environmental variables that affect the offspring or the mother's HPA function can also powerfully influence offspring development (Moriceau and Sullivan, 2006;Parker et al, 2006;Tang et al, 2006;Benetti et al, 2007;Akers et al, 2008;Raineki et al, 2010;Catalani et al, 2011). Most importantly, in studies using the postnatal/neonatal handling procedure, maternal care is intrinsically confounded with the maternal stress hormone and with offspring's stress experience (see Materials and Methods) (Russell, 1971;Daly, 1973;Tang, 2001), and these confounding factors cannot be ruled out by using a cross-fostering experimental design as by Liu et al (1997) and Francis et al (1999).…”

“…The present study used the neonatal novelty exposure with a split-litter design that both isolates the novelty exposure manipulation of the offspring from maternally related and other confounding factors and allows separate observations of potential noveltyexposure-induced preferential maternal care (Tang et al, 2006;Benetti et al, 2007), and it demonstrated the following: first, separate contributions to cognitive development made by maternal self-stress regulation and postnatal environmental novelty; and second, revealing a nonmaternal early environmental factor and a modulatory, instead of mediatory, relationship between maternal individual differences in self-stress regulation and novelty effects on offspring cognitive development. Together, our findings, along with previous studies, support a broader view on the maternal contribution to offspring development-to include maternal self-stress regulation in addition to maternal care.…”

Minimizing fear and anxiety in working dogs: A review

“…Early and abrupt separation also enhances manifestations of anxiety and depression-like behaviors (Fabricius et al, 2008;Lambás-Señas et al, 2009) and impairs spatial learning and memory (Aisa et al, 2007;Tata et al, 2015) during adulthood. In contrast, repeated, short maternal separation increased resilience to stressful events later in life (Parker et al, 2006;Benetti et al, 2007) and reduced fearfulness (Macrì and Würbel, 2006). The positive effects of such separations may have resulted from increased attention from the mother when the pups were returned.…”

Pre- and postnatal evaluation of offspring rats exposed to Origanum vulgare essential oil during mating, gestation and lactation

“…The results obtained in the open field test showed that the treatment of rat dams with oregano essential oil did not affect the emotional state of the offspring. Studies have shown that stressful stimuli during the period of sexual differentiation of the central nervous system, prenatal and soon after birth induce stable changes manifested by decreased sexual behavior in male and female rats (BENNETI et al, 2007).…”