Experiments were designed to address two goals: mapping the brain-wide distribution of c-Fos and, in the same mice, establishing the feasibility of controlling neural ensembles activated by psilocybin using the TRAP2 mouse line. In TRAP2 mice (Fos::c-Fos-2A-iCreERT2 knock-in; RRID:IMSR_JAX:030323), c-Fos and iCreERT2 are expressed in cells with Fos promoter activity and separated via ribosomal skipping of the 2A coding sequence during translation. Injection of 4-hydroxytamoxifen (4-OHT) activates iCreERT2, enabling translocation from the cytosol to the nucleus for site-specific recombination. TRAP2 mice were crossed to an Ai14 reporter line (Rosa-CAG-LSL::tdTomato; RRID:IMSR_JAX:007914) (Allen et al., 2017 (link)) for visualization of activated neurons via conditional tdTomato expression. Prior to the TRAPing timepoint, mice were naïve to experiments and treatments.
Twenty-five male and 8 female TRAP2;Ai14 mice (12–18 weeks of age) were bred in house to C57BL6/J wild type mice to give littermates of TRAP2+/− or TRAP−/−, and Ai14+/+, Ai14+/− or Ai14−/− genotypes (Transnetyx; Cordova, TN); a subset of mice (16 males and 6 females, TRAP+/−;Ai14+) was used to assess the feasibility of genetically labeling psilocybin-activated neural populations. Animals were maintained in age- and sex-matched groups of 2–5 littermates and housed in an 12:12 light-dark cycled SPF facility and appeared to be in good health; male mice weighed 31.4 ± 0.7 g (mean ± SEM) and females weighed 23 ± 0.9 g. Home cages were sterile ventilated cages by Innovive (San Diego, CA) offering irradiated 1/8” corn cob bedding (The Andersons, Inc.) with ad libitum access to pre-filled acidified water bottles (Innovive) and irradiated 18% protein rodent diet (Teklad Global). All animal behavioral procedures comply with the ARRIVE guidelines (Sert et al., 2020 (link)), the Guide for the Care and Use of Laboratory Animals (Council, 2011), and were approved by the Stanford University Institutional Animal Care and Use Committee. The animal care and use program is fully accredited by AAALAC, International and holds an Assurance with OLAW.
Twenty-five male and 8 female TRAP2;Ai14 mice (12–18 weeks of age) were bred in house to C57BL6/J wild type mice to give littermates of TRAP2+/− or TRAP−/−, and Ai14+/+, Ai14+/− or Ai14−/− genotypes (Transnetyx; Cordova, TN); a subset of mice (16 males and 6 females, TRAP+/−;Ai14+) was used to assess the feasibility of genetically labeling psilocybin-activated neural populations. Animals were maintained in age- and sex-matched groups of 2–5 littermates and housed in an 12:12 light-dark cycled SPF facility and appeared to be in good health; male mice weighed 31.4 ± 0.7 g (mean ± SEM) and females weighed 23 ± 0.9 g. Home cages were sterile ventilated cages by Innovive (San Diego, CA) offering irradiated 1/8” corn cob bedding (The Andersons, Inc.) with ad libitum access to pre-filled acidified water bottles (Innovive) and irradiated 18% protein rodent diet (Teklad Global). All animal behavioral procedures comply with the ARRIVE guidelines (Sert et al., 2020 (link)), the Guide for the Care and Use of Laboratory Animals (Council, 2011), and were approved by the Stanford University Institutional Animal Care and Use Committee. The animal care and use program is fully accredited by AAALAC, International and holds an Assurance with OLAW.
