γ > 0 represents the gain of the nAChR activation of the DA fibers, and σ > 0 is related to the “affinity” of the nAChRs on DA fibers to the activation of CIN (i.e., σ = 1 means that the nAChRs on GINs and on DA respond with identical sensitivity to CIN activity). The gene discussed is CHRNA4; the disease is cervical squamous intraepithelial neoplasia.