Maternal separation alters drug intake patterns in adulthood in rats

Abstract

Maternal separation/handling (MS/H) is an animal model of early life stress that causes profound neurochemical and behavioral alterations in pups that persist into adulthood. Many recent studies have used the MS/H model to study changes in drug effects in adulthood that are linked to behavioral treatments and stressors in the perinatal period. The drug effects focused on in this review are the reinforcing properties of the abused drugs, cocaine and alcohol. A striking finding is that variations in maternal separation and handling cause changes in ethanol and cocaine self-administration. Further, these changes indicate that various manipulations in the perinatal period can have long lasting effects of interest to biochemical pharmacologists. This article will review recent studies on ethanol and cocaine self-administration using the MS/H model and the neurochemical alterations that may play a role in the effects of MS/H on ethanol and cocaine self-administration. Studying the MS/H model can provide important clues into the vulnerability to drug abuse and perhaps identify a crucial window of opportunity for therapeutic intervention.

Figure 1

Ethanol preference among different maternally separated groups (n = 8-9 litters/group). Data for each group represent mean ± SEM. After significant differences were found between the groups with a one-way ANOVA, individual comparisons were done using Tukey’s multiple comparison test. Differences in letters on bars indicate a significant difference. a vs b, P<0.05; a vs c, P<0.001; b vs c, P<0.001; c vs ab, P<0.001; a vs ab and b vs ab, no significant difference. Thus MS/H treatments in the neonatal period change the propensity to SA alcohol when they are adults. This figure is from Jaworski et al [22].

Figure 2

The effects of experimental treatments (Table 1) on the average cocaine intake (mg) per session of the maternally separated and non-handled adults. The data points represent the group means ± SEM. * p < 0.05 NH vs MS15 at the same dose. ** p < 0.01 NH vs MS15 at the same dose. Significant differences were found at other doses as well. Thus, MS/H treatments alter the propensity of adult rats to SA cocaine. Data from Moffett et al, (46).