Caloric Restriction in Group-Housed Mice: Littermate and Sex Influence on Behavioral and Hormonal Data

This study was partially funded by the Master's program in Basic and Applied Neuroscience and Pain, University of Granada, the Junta de Andalucia (grants CTS109 and B-CTS-422-UGR18) and the Spanish Ministry of Health (National Drug Plan grant 2020I049). AV-A was recipient of a predoctoral fellowship (Grant/Award number: FPU18/05012) of the Ministerio de Universidades, Spain. LR-L has a research contract under the grant B-CTS-422-UGR18 (Programa Operativo FEDER Andalucia 2014-2020).We acknowledge the technical assistance of Ms. Ana Fernández Ibáñez, who helped with the ACTH hormone analysis, and of Mr. Daniel González Fernández, who edited the final English version of this document.Much of the research done on aging, oxidative stress, anxiety, and cognitive and social behavior in rodents has focused on caloric restriction (CR). This often involves several days of single housing, which can cause numerous logistical problems, as well as cognitive and social dysfunctions. Previous results in our laboratory showed the viability of long-term CR in grouped rats. Our research has studied the possibility of CR in grouped female and male littermates and unrelated CB6F1/J (C57BL/6J x BALBc/J hybrid strain) mice, measuring: (i) possible differences in body mass proportions between mice in ad libitum and CR conditions (at 70% of ad libitum), (ii) aggressive behavior, using the number of pushes and chasing behavior time as an indicator and social behavior using the time under the feeder as indicator, and (iii) difference in serum adrenocorticotropic hormone (ACTH) concentrations (stress biomarker), under ad libitum and CR conditions. Results showed the impossibility of implementing CR in unrelated male mice. In all other groups, CR was possible, with a less aggressive behavior (measured only with the number of pushes) observed in the unrelated female mice under CR conditions. In that sense, the ACTH levels measured on the last day of CR showed no difference in stress levels. These results indicate that implementantion of long-term CR in mice can be optimized technically and also related to their well-being by grouping animals, in particular, related mice.Master's program in Basic and Applied Neuroscience and Pain, University of GranadaJunta de Andalucia CTS109 B-CTS-422-UGR18Spanish Ministry of Health (National Drug Plan grant) 2020I049Ministerio de Universidades, Spain FPU18/05012Programa Operativo FEDER Andalucia B-CTS-422-UGR1