Circadian Rhythms and Autonomic Function

Abstract

This chapter focuses on the role of circadian rhythms and autonomic function within suprachiasmatic nuclei (SCN). Within the SCN, rhythms are generated in circadian pacemaker cells by a complex of molecular feedback loops that positively and negatively regulate the transcription of core genes of the circadian clock. The output of the SCN includes both humoral and neural mechanisms, which are directly related to the autonomic nervous system and, in turn, to the circadian regulation of body functions. The SCN regulates pineal function by innervation of paraventricular (PVN) neurons which project to preganglionic neurons in the intermediolateral nucleus of the thoracic spinal cord, which in turn project to the noradrenergic neurons of the superior cervical ganglion (SCG). The light-dark cycle influences autonomic activity, and it has been demonstrated that this regulation depends on the SCN, since lesions of the nuclei eliminate photic modulation. The SCN sends neural projections to other hypothalamic nuclei and from there to the brainstem or spinal cord autonomic centers that control physiological activity.