Lactation does not alter the long-term stability of individual differences in behavior of laboratory mice on the elevated plus maze

Abstract

Individual consistency over time in behavioral responses to challenging situations is usually regarded as an indication of the existence of animal personality types. Although such consistency has been found in a variety of species, information about long-term stability is scanty, in particular across different life history stages, for example reproductive and non-reproductive periods, which have the potential to affect substantially the behavioral responses of animals. In our study of adult female laboratory mice, we explored the stability of behavioral responses across a 43-day period by successively testing the animals on an elevated plus maze. We tested two groups, one group that had offspring during the first two tests but not during the last test, and another group that only had offspring during the last test. We found clear evidence of individual consistency over time by means of positive significant correlations across the different tests: animals that spent more time in the closed arms and those that entered the open arms more often during the first test also tended to do so during the second test-when still in the same reproductive state, and also during the third test-when in a different reproductive state. In addition, females of the two groups did not differ overall in their responses, although we found a significant increase in the frequency and duration of presumed anxiety-related behavior during the course of the experiment, contradicting the notion that habituation effects should attenuate the challenge of the test situation. In conclusion, our study strongly suggests the existence of stable personality types in female laboratory mice, even across different reproductive stages.

Differential postpartum sensitivity to the anxiety-modulating effects of offspring contact is associated with innate anxiety and brainstem levels of dopamine beta-hydroxylase in female laboratory rats

“…Anxiety-related behavior in nulliparous female laboratory rodents is stable across many months (Leibsch et al, 1998; Henniger et al, 2000; Curley et al, 2012), suggesting the existence of an ongoing “trait” anxiety (Gosling, 2001). It is unknown whether or not anxiety-related behavior in our least-anxious and most-anxious rats continues to be predictable after the first week postpartum, but this may be likely because there is a significant correlation between the anxiety of randomly selected female mice tested during the first postpartum week and again several days post-weaning (Rödel et al, 2012). Furthermore, mother rhesus monkeys show stable anxiety across multiple births spanning years (Maestripieri, 2000).…”

Lifetime development of behavioural phenotype in the house mouse (Mus musculus)

“…In addition, divergent results found in different traits and testing setups might be due to differences in relative importance of changes in brain and physiology [ 116 ]. Good evidence for individual stability in performance comes from [ 117 ], who found female outbred mice (strain RjHan:NMR1) to remain stable in their anxiety-related behaviour measured in an elevated plus-maze at PND 90 and PND 135, regardless of changes in their reproductive state. In inbred mice behavioural stability was demonstrated in a study [ 6 ] by showing that male mice (strain C57BL/6N) were stable in their anxiety-related behaviour measured in an elevated plus-maze around PND 60 and PND 90.…”

“…Interestingly, both studies report behavioural consistencies despite considerable inter-individual variability. Possibly some of the variability was experimentally induced by either including two groups of females with different breeding experiences [ 117 ] or different subgroups of mice that were housed in either stable or instable social groups [ 6 ].…”

“…Additionally, there was no effect on long term stability of behaviour in lactating compared to non-lactating females in an elevated plus maze. This suggests that the reproductive state may not influence the stability of these behavioural traits [ 117 ]. Hence, except for minor (and possibly temporary) variations, behaviour remains relatively stable during the phase of adulthood.…”

Affective changes during the postpartum period: Influences of genetic and experiential factors

“…Without this move toward the middle, the subpopulation of dams that are especially low in anxiety may be under-aroused and neglectful of cues coming from the litter and other aspects of their environment, while dams that are especially high in anxiety may be over-aroused and unnecessarily responsive. It is unknown how long females' premating trait-like anxiety can predict their anxiety-related behaviors after reproducing, but anxiety in mice tested during the first week postpartum is highly correlated with their anxiety tested again after weaning the pups (Rodel et al, 2012). Even more suggestive of very long-term predictive value of a females' traitlike anxiety is that female rhesus monkeys show stable anxiety-related behavior across series of births that span years (Maestripieri, 2000).…”