Breeding and genotyping
The 5-HT2CR KO and WT animals used in Experiment 2 were of a C57BL/6J background generated as previously described [16]. The original progeny of 5-HT2CR KO mice used here were a gift from L. Tecott and produced as described by [29]. Wild-type male mice were crossed with females heterozygous for the X-linked 5-HT2CR mutation generating male WT and KO offspring. Genotyping was achieved using PCR on tissue samples from ear punches. The wild-type allele was detected using primers of the 5-HT2CR gene sequences flanking the Neo insertion: m5h2c (5′-AGTTGATGTTCATCTCAGGTGGC-3′) and 3N2 (5′-GGGTCCTATAGATCGAGGTACC-3′). The mutant allele was detected using primers complimentary to neomycin resistance gene (Neo) sequences: NeoD (5′-CACCTTGCTCCTGCCGAGAAA-3′) and NeoH (5′-AGAAGGCGATAGAAGGCGATG-3′). Breeding animals had been backcrossed for more than 20 generations and the individuals used here were 10–24 weeks old (age-matched for genotype) at the beginning of the experiment.