A Model of Suprachiasmatic Nucleus Firing Rate in the Rodent

The biological clock in mammals controls many important behavioral functions, one of which is sleep and wake patterns. It has been well established that this circadian pacemaker is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Lesions of the SCN have been shown to entirely eliminate circadian patterns of sleeping and waking, indicating that the SCN is completely necessary for circadian regulation of sleeping and waking in mammals. Neurotransmitters play a very important role in the SCN and how it controls sleeping and waking; namely, neurotransmitters mediate circadian signaling from the SCN and act within the SCN to influence the activity of SCN neurons. Mathematical modeling has previously been done to analyze the sleep wake patterns of mammals, specifically rodents, and how these patterns are controlled by different neurotransmitters. These models have represented the difference in light and dark sleep and wake patterns with different parameter values. Modeling has yet to delve into the role that the circadian clock in the SCN plays in the sleeping and waking of rodents. We have developed an SCN firing rate model that explores the circadian regulation of the SCN and consequently, the circadian regulation of sleeping and waking over a 24 hour period. The model takes into consideration projections to and from the SCN and their excitatory and/or inhibitory effects on sleeping and waking.