Effects of Neonatal Fluoxetine Exposure on Behavior Across Development in Rats Selectively Bred for an Infantile Affective Trait
Infants born to depressed mothers are at higher risk for insecure attachment and behavioral problems. Thus, current medical practice is to continue psychotropic medication of pregnant women with depression despite concerns about its behavioral teratology. There are few animal studies focused on long-term behavioral effects of prenatal antidepressant exposure; in addition, studies have not looked at individual differences in baseline affective state as a source of response variability. In this study, fluoxetine, a common SSRI, was administered to rat pups from postnatal day 2 to 7 to model exposure to antidepressants in the human third trimester. Five behavioral measures were conducted from the neonatal to adult age periods in Low and High lines selectively bred for their rate of ultrasonic vocalizations after brief maternal separation. Neonatal fluoxetine administration decreased distress calls to a greater extent in High line rats than Lows, however this reduction in anxiety behavior was not found in juveniles or adults. Fluoxetine impaired coordination in neonates and increased activity in juveniles; these results suggest a drug-related developmental delay in motor systems. Neonatal fluoxetine effects persisted into adulthood, as seen in a measure of social interaction. These results suggest not only that there are long-term behavioral consequences of SSRI use during late pregnancy, but that baseline affect may be an important indicator of sensitivity to these adverse effects.
Investigating the Effects of Early Deprivation on Prosocial Behavior
The Early Deprivation (ED) animal model of human child neglect is useful for examining the consequences of early life stress on subsequent behaviors across the lifespan. In this model, neonatal rat pups are isolated from the dam and littermates for 3 hours daily for the first week of life. While ED has been shown to cause cognitive and learning deficits, the effects of ED on prosocial behavior, measured by releasing a trapped cagemate, have not been studied. In the present study, ED and control rats were tested as juveniles for emergence and open field activity and as adults for social recognition and prosocial behavior. As juveniles, ED males showed a feminization effect, matching the elevated activity levels and lower emergence latencies of control and ED females. As adults, the sex effect was reversed: females showed a weaker tendency to free their cagemate and a longer latency to do so than males. ED females seemed especially prosocially impaired, and observed social behavior with the cagemate supports this conclusion. These results in the context of the current literature suggest that further honing of the methods studying prosocial behavior is required. The present study, however, provides useful insight into the life-long effects of early life stressors in rodents and their parallels to human ontogeny.