In the present study, we analyzed changes in the expression of genes associated with regulation of the sleep–wake cycle (Hnmt, Hrh1, Hrh3, Per1, Per2, and Chrm3) in the SN and striatum of mice of different ages in normal mice, and in young and adult mice with the MPTP model of the ESS of PD. The gene discussed is HRH3; the disease is Parkinson disease.