Extensive juvenile “babysitting” facilitates later adult maternal responsiveness, decreases anxiety, and increases dorsal raphe tryptophan hydroxylase‐2 expression in female laboratory rats

Abstract

Pregnancy and parturition can dramatically affect female neurobiology and behavior. This is especially true for laboratory-reared rodents, in part, because such rearing prevents a host of developmental experiences that females might undergo in nature, including juvenile alloparenting. We examined the effect of chronic exposure to pups during post-weaning juvenile life (days 22-36) on adult maternal responsiveness, anxiety-related behaviors, and dorsal raphe tryptophan hydroxylase-2 (TPH2) and serotonin transporter (SERT) levels in nulliparous rats. Adult females with juvenile alloparental experience showed significantly faster sensitized maternal responsiveness, less anxiety, and more dorsal raphe TPH2. Juvenile alloparenting did not affect females' later social novelty and preference behaviors toward adults, suggesting their increased interest in pups did not extend to all social partners. In a second experiment, suckling a pregnant dam (achieved by postpartum estrus reinsemination), interacting with her after standard laboratory weaning age, and a 3-day exposure to younger siblings also reduced juvenile females' later anxiety but did not affect maternal responsiveness or TPH2. Thus, extensive juvenile "babysitting" can have long-term effects reminiscent of pregnancy and parturition on maternal responsiveness and anxiety, and these effects may be driven by upregulated serotonin. © 2016 Wiley Periodicals, Inc. Dev Psychobiol 58: 492-508, 2016.

Serotonin-specific lesions of the dorsal raphe disrupt maternal aggression and caregiving in postpartum rats

“…We have no obvious explanation for this difference, but pre- and postpartum rats may differ in the abundance, affinity, or efficiency of DR SERT; the degree to which SERT is transported to the plasma membrane; or levels of extracellular serotonin that would affect competitive binding for reuptake. In fact, a study run in our laboratory contemporaneous to the present studies found that postpartum rats had ~30% more SERT in the DR compared to nulliparous virgin females [106].…”

The Neurobiology of Postpartum Anxiety and Depression

“…The neurochemicals acting in these sites to modulate postpartum anxiety in postpartum laboratory rodents include norepinephrine, serotonin, and corticotropin releasing hormone [66,[68][69][70].…”

The neurobiological causes and effects of alloparenting

“…On the other hand, extensive alloparental experience in virgin female rats for either 3 or 14 days reduces the expression of anxiety‐related behaviors as well as increases the expression of the rate‐limiting enzyme for serotonin synthesis in the 14 day condition (Harding and Lonstein, ). Similar results were seen in the alloparental African striped mouse ( Rhabdomys pumilio ), where alloparenting experience resulted in less anxiety‐related behavior in females (Pillay and Rymer, ).…”