The Role of Orexin in Avian Migration
Open Access
- Author:
- Wiederer, Mc Rae
- Area of Honors:
- Animal Sciences
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Paul Allen Bartell, Thesis Supervisor
William Burton Staniar, Thesis Honors Advisor
Robert John Vansaun, Faculty Reader - Keywords:
- white-throated sparrow
nocturnal migration
orexin
immunohistochemistry - Abstract:
- Songbirds are typically diurnal. However, during the migratory period, they will adopt a nocturnal pattern and fly throughout the night. Songbirds kept in a laboratory environment, though unable to migrate, will still exhibit nocturnal restlessness, or Zugunruhe, during their migratory period. While the exact neurobiological cause of this switch from diurnal to nocturnal behavior is yet unknown, it may be related to activity of the neuropeptide orexin, also known as hypocretin. Orexin is known to regulate appetite and feeding, arousal and energy levels, sleep/wake cycles, and dopaminergic activity in mammals. Orexin functions by binding G protein coupled receptors (GPCRs), of which there are two subtypes, A and B, in order to activate second-messenger signaling pathways to regulate these processes. This study utilized immunohistochemistry to selectively stain against orexin receptors A and B in the brains of white-throated sparrows that were exhibiting Zugunruhe and those that were not exhibiting Zugunruhe. Results showed a consistent distribution of orexin in several regions of the avian brain, including the ventral tegmental area (VTA), periaqueductal gray (PAG), and Purkinje cells of the cerebellum. The PAG is involved in regulating rapid eye movement (REM) sleep and the VTA is involved in regulating non-REM sleep, both of which are processes that are altered during migration. Additionally, the VTA contributes to the neural reward pathway, thought to be a component of migratory drive, and the Purkinje cells of the cerebellum are thought to help regulate respiratory and cardiac function in relationship with increased locomotor activity. Taken together, these findings implicate a role for orexin in regulating nocturnal avian migration at multiple levels.