Strain specific analysis of Mc4r mRNA expression in wild-type C57BL/6 mice and B-Mc4r KO mice by RT-PCR. Spinal cord RNA was isolated from wildtype C57BL/6 mice (+/+) and homozygous B-Mc4r KO mice (-/-), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse Mc4r primers. Mouse Mc4r mRNA was detectable in wild-type C57BL/6 mice but not in B-Mc4r KO mice.