Corticosterone Pathway in Torpor
In a study of the effects of the hormone corticosterone (CORT) on torpor in rufous hummingbirds, it was decided that corticosterone had some part in the regulation of torpor in rufours hummingbirds (Hiebert 2000). Administration of CORT in the food of humminbirds resulted in increased use of torpor and decreased food intake. This data would indicate that CORT has some important part in the biochemical pathways involved in torpor.
Nonetheless, measurements of naturally occurring CORT in hummingirds during different seasons yielded conflicting data. While CORT concentrations at night increased during migratory periods when hummingbirds had calorie restricted diets, there was no connection between calorie restriction and CORT concentrations during the molting period. Additionally, in migratory periods, CORT concentrations increased steadily throughout the day while in the molting period the reverse pattern occurred. All of this information indicates that while CORT does seem to have some important part in the biochemical pathways of hummingbird torpor, there must be some other "feature of the CORT signal other than concentration" that explains its function (Hiebert 2000).
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