Editing Suprachiasmatic nucleus (section)

===Behaviors controlled by the SCN of vertebrates===

Significant research has been conducted on the genes responsible for controlling circadian rhythm, in particular within the SCN. Knowledge of the gene expression of [[Clock gene|''Clock'' (''Clk'')]] and [[PER2|''Period2'' (''Per2'')]], two of the many genes responsible for regulating circadian rhythm within the individual cells of the SCN, has allowed for a greater understanding of how genetic expression influences the regulation of circadian rhythm-controlled behaviors.<ref name=":6" /> Studies on [[thermoregulation]] of [[ruin lizard]]s and mice have informed some connections between the neural and genetic components of both vertebrates when experiencing induced hypothermic conditions.<ref name="mag" /> Certain findings have reflected how evolution of SCN both structurally and genetically has resulted in the engagement of characteristic and stereotyped thermoregulatory behavior in both classes of vertebrates.

*'''Mice''': Among vertebrates, it is known that mammals are endotherms that are capable of homeostatic thermoregulation. It has been shown that mice display thermosensitivity within the SCN. However, the regulation of body temperature in [[Hypothermia|hypothermic]] mice is more sensitive to the amount of light in their environment.<ref name="toki" /> Even while fasted, mice in darkened conditions and experiencing hypothermia maintained a stable internal body temperature.<ref name="toki" /> In light conditions, mice showed a drop in body temperature under the same fasting and hypothermic conditions. Through analyzing genetic expression of ''Clock'' genes in wild-type and knockout strains, as well as analyzing the activity of neurons within the SCN and connections to proximate nuclei of the hypothalamus in the aforementioned conditions, it has been shown that the SCN is the center of control for circadian body temperature rhythm.<ref name="toki">{{cite journal | vauthors = Tokizawa K, Uchida Y, Nagashima K | title = Thermoregulation in the cold changes depending on the time of day and feeding condition: physiological and anatomical analyses of involved circadian mechanisms | journal = Neuroscience | volume = 164 | issue = 3 | pages = 1377–86 | date = December 2009 | pmid = 19703527 | doi = 10.1016/j.neuroscience.2009.08.040 | s2cid = 207246725 }}</ref> This circadian control, thus, includes both direct and indirect influence of many of the thermoregulatory behaviors that mammals engage in to maintain homeostasis.
*'''Ruin lizards''': Several studies have been conducted on the genes expressed in circadian oscillating cells of the SCN during various light and dark conditions, as well as effects from inducing mild hypothermia in reptiles. In terms of structure, the SCNs of lizards have a closer resemblance to those of mice, possessing a dorsomedial portion and a ventrolateral core.<ref name="cas">{{cite journal | vauthors = Casini G, Petrini P, Foà A, Bagnoli P | title = Pattern of organization of primary visual pathways in the European lizard Podarcis sicula Rafinesque | journal = Journal für Hirnforschung | volume = 34 | issue = 3 | pages = 361–74 | date = 1993 | pmid = 7505790 }}</ref> However, genetic expression of the circadian-related ''Per2'' gene in lizards is similar to that in reptiles and birds, despite the fact that birds have been known to have a distinct SCN structure consisting of a lateral and medial portion.<ref name="abe">{{cite journal | vauthors = Abraham U, Albrecht U, Gwinner E, Brandstätter R | title = Spatial and temporal variation of passer Per2 gene expression in two distinct cell groups of the suprachiasmatic hypothalamus in the house sparrow (Passer domesticus) | journal = The European Journal of Neuroscience | volume = 16 | issue = 3 | pages = 429–36 | date = August 2002 | pmid = 12193185 | doi = 10.1046/j.1460-9568.2002.02102.x | s2cid = 15282323 }}</ref> Studying the lizard SCN because of the lizard's small body size and ectothermy is invaluable to understanding how this class of vertebrates modifies its behavior within the dynamics of circadian rhythm, but it has not yet been determined whether the systems of cold-blooded vertebrates were slowed as a result of decreased activity in the SCN or showed decreases in metabolic activity as a result of hypothermia.<ref name="mag"/>