Cba j

A total of 23 mouse strains (129X1/SvJ, A/J, AKR/J, B10.S-H2s/SgMcdJ (B10.S), BALB/cJ, BPL/1J, BPN/3J, C3H/HeJ, C57BL/6J, C57BL/10J, CBA/J, CZECHII/EiJ, DBA/1J, DBA/2J, FVB/NJ, JF1/MsJ, MOLF/EiJ, MRL/MpJ, NOD/ShiLtJ, NU/J, PWD/PhJ, PWK/PhJ, SJL/J and SWR/J were purchased from the Jackson Laboratory (Bar Harbor, ME). All mice, including B10.S-Histh^SJL and B10.S-Histh^SJL ISRC lines, were generated and maintained under specific pathogen-free conditions in the vivarium of the Given Medical Building at the University of Vermont according to National Institutes of Health guidelines. All animal studies were approved by the Institutional Animal Care and Use Committee of the University of Vermont.

Mice were 6–12 weeks old at the time of experiments. Mice were acquired from Jackson Laboratories: C57BL/6J; CBA/J; Slc32a1^tm2(cre)Lowl/J (VGAT-Cre); Pvalb^tm1(cre)Arbr/J (PV-Cre); Gt(ROSA)26Sor^{tm9(CAG-tdTomato)Hze}/J (Ai9). For Fig. 6, data from our previous studies were reanalyzed (Aponte et al. 2021 (link); Kline et al. 2021 (link); Onodera and Kato 2022 ). For this dataset, additional mice were acquired from Jackson Laboratories (Sst^{tm2.1(cre)Zjh}/J (Sst-Cre)) and MMRRC (Tg(Rbp4-Cre)KL100Gsat/Mmucd (Rbp4-Cre); Tg(Tlx3-Cre)PL56Gsat/Mmucd (Tlx3-Cre)). Both female and male animals were used and housed at 21 °C and 40% humidity with a reverse light cycle (12–12 h). All experiments were performed during their dark cycle. All procedures were approved and conducted in accordance with the Institutional Animal Care and Use Committee at the University of North Carolina at Chapel Hill as well as the guidelines of the National Institutes of Health.

The subjects were adult (aged 7–9 weeks at time of liver dissection) male and female mice of eight inbred mouse strains: 129X1/SvJ, BALB/cJ, C57BL10/J, FVB/nJ (“short” allele strains) and A/J, C3H/HeJ, CBA/J, NOD/ShiLtJ (“long” allele strains) (n = 7 per sex per strain, with the exception of C57BL/10J, which had only 4 females; Jackson Laboratory, Bar Harbor, ME, USA). Mice were group-housed in the same colony room with a 12 h light/dark cycle and ad libitum access to food and water. Subjects were acclimated to the colony room over a seven-day period following their arrival, after which liver dissections were performed. For Experiment 2, subjects did not receive any experimental manipulation prior to euthanasia. All procedures were performed in accordance with the NIH Guide for the Care and Use of Laboratory Animals and were approved by the Pennsylvania State University IACUC committee.

All mice were housed at University of Virginia specific pathogen-free facilities with a 12 hr light/dark cycle. C57BL/6 J (#000664), CBA/J (#000656), B6.Cg-Tg(Itgax-Venus)1Mnz/J (CD11c^YFP mice, #008829), C57BL/6-Tg(TcraTcrb)1100Mjb/J (OT-I mice, #003831), and C57BL/6-Tg(Nr4a1-EGFP/cre)820Khog/J (Nr4a1^GFP mice, #016617) strains were originally purchased from the Jackson Laboratory and then maintained within our animal facility. B6.SJL-Ptprc^aPepc^b/BoyCrCrl (CD45.1 congenic mice, #564) and Swiss Webster (#024) strains were purchased from Charles River Laboratories. To generate OT-I (CD45.1 congenic) mice, OT-I and CD45.1 congenic strains were cross-bred within our facility. OT-I (CD45.1 congenic) mice were then crossed to Nr4a1^GFP mice to generate OT-I/Nr4a1^GFP (CD45.1 congenic) mice for use in adoptive transfer studies. For experiments reported in this study, age-matched young adult female mice (7–10 weeks of age) were used. All experiments were approved by the Institutional Animal Care and Use Committee at the University of Virginia under protocol number 3968.

Subjects included 281 experimentally naïve (age-matched 8–16 or 78 weeks) adult male and female mice from the following strains: AKR/J (AKR; N=52; 26/sex), DBA/2 (DBA; N=49; 25 male and 24 female), CBA/J mice (CBA; N=86; 43/sex), and C57BL/6J (B6; N=94; 47/sex). Mouse strains were chosen based on previous work by Kest et al. (1999 (link)) examining sex differences in morphine-induced antinociception dose-response curves across these mouse strains. All mice were obtained from Jackson Laboratories: [C57BL/6J (#000664); DBA/2 (#000671); AKR (#000648); CBA/J (#000656)]. B6 and AKR mouse strains were chosen because morphine produced increased antinociception in males compared to females while CBA females showed the opposite. In contrast, there were no sex differences in morphine-induced antinociception in DBA mice as a function of sex. Mice were group housed (3–5/cage) on a 12:12 hour light/dark cycle (lights out at 18:00) with ad libitum access to food and water. Female mice were not monitored for estrus cycle. Mice were weighed daily prior to any administration of drug to ensure proper dosing. Animal care procedures were conducted in accordance with NIH guidelines for the Care and Use of Laboratory Animals ( 2011 ) and with approval from Marshall University’s Institutional Animal Care and Use Committee (IACUC).