Small interfering RNAs can modulate transcriptional gene expression via epigenetic modulation of targeted promoters. Endogenous effects can modulate and regulate systems, in conjunction with environmental influences. This allows muscarine to modulate cellular excitability via the membrane potential. In general, epigenetic alteration can modulate gene expression. Cofactors are proteins that modulate the effects of transcription factors. In addition, various plasmid-encoded cytokines modulate the immune system differently according to the delivery time. At millimolar concentrations, they may also modulate the redox state of the NMDA receptor complex. Nicotine can modulate the firing rate of the ventral tegmental area neurons. These effects can all modulate the transcription of genes. CD9 can also modulate cell adhesion and migration. Androgens may modulate the physiology of vaginal tissue and contribute to female genital sexual arousal. In this way, CD19 can modulate the threshold for B cell activation. Histone deacetylase inhibitors may modulate the latency of some viruses, resulting in reactivation. Microfilariae can also modulate the immune system to avoid destruction. In addition, they modulate muscarinic potassium channels.