Abstract: Per2 gene plays one of the most critical roles of clock gene which modulates circadian rhythm both in the physiological, biochemical and behavioral processes of organisms. The distributions of per2 gene include suprachiasmatic nucleus of the hypothalamus, central nucleus of amygdala, bed nucleus of the stria terminalis, hippocampus and other components of limbic system; it affects the emotional and visceral activities through participating in the system of circadian rhythm. The central per2 gene regulates the hypothalamus-pituitaryadrenal axis through integration of light input, steroid hormones and other neurotransmitters integration, acting on the target organs, and presentes a circadian rhythm of movement. This article reviewed the morphology and biology of per2 gene, and its participation in limbic system regulating the circadian rhythm of motional and visceral activities.

Key words: per2 gene, limbic system, circadian rhythm, clock gene, visceral motility, review