As can be seen from Table 2 and Figure 2, for all the genes under study (Hnmt, Hrh1, Hrh3, Per1, Per2, and Chrm3), a significant increase in the expression levels by 1.5 and more times in the SN of adult mice with the MPTP-induced model of the ESS of PD relative to adult healthy mice was detected. The gene discussed is HRH3; the disease is Parkinson disease.