(Class of 2001)

Advisor:  Dr. Loraina Ghiraldi, Psychology Department

SLU Festival of Science 2001 - Poster Presentation
 

The present study was designed to assess the effects of prenatal stress and subsequent early postnatal manipulations on inter-male aggression and marking behavior in adult mice.  Previous research has shown that prenatal stress disrupts a variety of hormonally mediated behaviors (e.g., Kinsley & Svare, 1985).

In this study, pregnant Swiss-Webster albino mice were subjected to heat, light and restraint stress during the last 6 days of gestation.  On the day of delivery, the litters were culled to 5 males and were randomly assigned to one of four postnatal treatments: one of two handling groups or one of two testosterone treatment groups.  The handling treatment, which entailed physically manipulating the pups, began on postnatal day 0 and occurred twice a day through postnatal day 21 (adapted from Fernandez-Teruel et al., 1991).  The nonhandled pups remained in the nest with the dam.  The testosterone group received subcutaneous injections of 200 mg of testosterone propionate (TP) dissolved in 0.2 ml sesame oil on days 1, 3, and 5 postpartum.  The control group received an oil vehicle.

At 22 days of age, the offspring were weaned and individually housed.  In adulthood (60-70 days of age), each male was concurrently tested for inter-male aggression (# of aggressive bouts) and social marking (# of urine deposits on opponent).  24 hr later, subjects were tested for environmental marking (quantification modified from Taylor & Bartko, 1984). Visibility of marking was enhanced by sodium fluorescein, a chemical that changes urinary color, especially under UV light.
 

Preliminary results suggest that prenatally stressed pups (oil controls) exhibit more environmental marking that normal (non-stressed) pups (p =.043).  In addition, pups treated neonatally with testosterone display significantly less environmental marking (p = .001), and a trend of less inter-male aggression (p = .083), than oil-treated pups.  The handling manipulation is still under analysis.

All subjects in the above groups were raised by stressed females; therefore, these results cannot be attributed to differential effects of mothering.  However, testing of additional experimental groups revealed that type of mothering may impact adult behavior.  For example, normal pups fostered to stressed females showed less aggression when compared to normal pups raised by non-stressed females.