Neonatal handling induces deficits in infant mother preference and adult partner preference

Abstract

Neonatal handling is an experimental procedure used to understand how early-life adversity can negatively affect neurobehavioral development and place animals on a pathway to pathology. Decreased preference for the maternal odor during infancy is one of many behavioral deficits induced by neonatal handling. Here, we hypothesize that deficits in maternal odor preference may interfere with partner preference in the adult. To test this hypothesis, we assessed infant maternal odor preference and adult partner preference in different reproductive stages in both male and female rats that received neonatal handling. Our results indicate that only neonatally handled females present deficits in maternal odor preference during infancy, but both male and females present deficits in adult partner preference. However, sexual experience was effective in rescuing partner preference deficits in males. These results indicate that, considering infant and adult social interactions, females are more susceptible to the effects of neonatal handling than males.

Neonatal handling: An overview of the positive and negative effects

“…In rats, neonatal handling negatively affects the neurocircuitry that supports social behavior, leading to pervasive deficits in social behavior throughout the lifespan. These negative effects can be observed as early as PN7, with handled females, but not males, showing reduced preference for the maternal odor, indicating a possible deficit in the mother–pup relationship (Raineki et al, 2009; Raineki, Lutz, Sebben, Ribeiro, & Lucion, 2013). Peripubertal rats handled during infancy also show a reduction in play behavior with littermates in the home cage (Karkow & Lucion, 2013), but exhibit more play behavior than non-handled controls when tested following a period of social isolation (Aguilar, Caramés, & Espinet, 2009; Siviy & Harrison, 2008).…”

“…In males, neonatal handling also reduces sexual behavior, including a significant decrease in the frequency of mounts with intromission (Padoin et al, 2001), as well as deficits in the motivational aspects of sexual behavior, such as reduced time spent investigating the sexual partner (Raineki et al, 2013). Neonatal handling also induces morphophysiological changes in the male reproductive system, such as reduced testicular weight, smaller seminiferous tubule diameter and decreased germinal epithelium thickness, all of which contribute to reductions in daily sperm production (Mazaro & Lamano-Carvalho, 2006).…”

Neonatal handling alters maternal emotional response to stress

“…The pups were handled during the light period of the daily photoperiod cycle (10:00–12:00) at a distance of approximately 100 cm from the mother. The total time of the mother–infant separation was approximately 90 s (Gomes et al, ; Padoin et al, ; Raineki et al, , , ; Todeschin et al, ).…”

“…Neonatal handling is an experimental procedure involving repeated, brief, maternal separation, and tactile stimulation during the first few days of life. This disruption of the mother–pup relationship is associated with persistent behavioral and neurochemical alterations in the pups over their life course such as decreased fear when exposed to novel environments (Padoin, Cadore, Gomes, Barros, & Lucion, ), decreased corticosterone secretion response to a variety of stressors (Liu, Caldji, Sharma, Plotsky, & Meaney, ; Plotsky & Meaney, ), altered feeding behavior and satiety (Silveira et al, ) and differential social behaviors and fertility in male and female rats (Gomes, Frantz, Sanvitto, Anselmo‐Franci, & Lucion, ; Raineki et al, , ; Raineki, Lutz, Sebben, Ribeiro, & Lucion, ; Reis et al, ). Besides these behavioral and neuroendocrine changes, neonatal handling also alters brain plasticity and neurotrophic signaling in the pups, producing long‐lasting structural changes (Lucion, Pereira, Winkelman, Sanvitto, & Anselmo‐Franci, ; Todeschin et al, ; Winkelmann‐Duarte et al, ).…”

Long‐Term Impact of Early Life Events on Physiology and Behaviour

“…Neonatally handled rats have reduced stress responses and increased exploratory behaviour in novel environments. However, neonatal handing reduces reproductive behaviour in both males and females . In males, lower testicular weight and reduced seminiferous tubule diameter and germinal epithelium thickness have been reported.…”