Housing and testing in mixed-sex rooms increases motivation and accuracy during operant testing in both male and female mice

Abstract

Operant behavior tasks are widely used in neuroscience research, but little is known about how variables such as housing and testing conditions affect rodent operant performance. We have previously observed differences in operant performance in male and female mice depending on whether mice were housed and tested in rooms containing only one sex versus rooms containing both sexes. Here, male and female mice in either single-sex or mixed sex housing rooms were trained on fixed ratio 1 (FR1) and progressive ratio (PR) tasks. For both sexes, animals in the mixed sex room had more accurate performance in FR1 and were more motivated in the PR task. We then moved the single sex housed animals to the mixed sex room and vice versa. Animals that started in mixed sex housing had no change to PR, but both sexes who started in single sex housing were more motivated after the switch. Additionally, the females that moved into single-sex housing performed less accurately in FR1. We conclude that housing and testing conditions can affect performance on FR1 and PR tasks. As these tasks are commonly used as training steps to more complex tasks, housing and testing conditions should be carefully considered during experiment design and reported in publications.

Living inside the box: environmental effects on mouse models of human disease

“…These and related observations have raised concerns about sanitation practices in mouse husbandry that can alter pheromonal signaling and potentially cause confounding effects in the research. Even the organization of a mouse room, segregating male and female mice, could have a significant effect on experimental results ( Bind et al, 2013 ; Lloyd et al, 2018 ). Evidence regarding the effects of human pheromones is highly controversial, but a recent paper suggests that this is one area where mice and humans might have rather distinct environmentally mediated communication mechanisms ( Hare et al, 2017 ).…”

Using touchscreen-delivered cognitive assessments to address the principles of the 3Rs in behavioral sciences

“…While more limited in use to date than the CB task, non-touchscreen versions of PR have provided some potential insights into husbandry practices. For example, housing conditions can impact PR performance in rats (mixed-sex vs. single-sex holding rooms 172 ) and in NHPs (single housing vs. pair-housing 173 ). These studies support the viability of using the PR schedule as a tool to assess the effect of husbandry-related factors on laboratory animal welfare.…”

Involvement of dopamine in the regulation of dysfunctions related to depression in rodent models: motivational versus emotional symptoms

“…Most of the animal studies that use operant tasks are performed in male rodents, although there is some literature on performance of female rodents in operant tasks. Thus, it has been observed that female mice lever-press less in a progressive ratio operant task (Lloyd et al, 2018), and the same pattern is observed in female rats using fixed ratios (van Haaren et al, 1990). However, so far there are no published studies assessing female performance in effort-based decision-making tasks.…”