OREXINS IN THE AVIAN BRAIN: COMPARISON OF HYPOTHALAMIC mRNA CONCENTRATIONS DURING THE DAY-NIGHT CYCLE AND AFTER FOOD RESTRICTION IN BROILER AND LAYER CHICKS AND IMMUNOISTOCHEMICAL LOCALIZATION IN CHICK HYPOTHALAMUS
Miranda, Bernadette (2011) OREXINS IN THE AVIAN BRAIN: COMPARISON OF HYPOTHALAMIC mRNA CONCENTRATIONS DURING THE DAY-NIGHT CYCLE AND AFTER FOOD RESTRICTION IN BROILER AND LAYER CHICKS AND IMMUNOISTOCHEMICAL LOCALIZATION IN CHICK HYPOTHALAMUS. [Tesi di dottorato]
Full text disponibile come:
The aim of this study was to describe the distribution pattern of orexin-ir neuronal elements in the hypothalamus of broiler chick and to test the eventual difference of orexin mRNA expression during day-night cycle and in feed and food restricted condition in broiler and layer chicks in order to made an attempt to clarify the role of orexins in the chick, a specie of birds very important in poultry production. The distribution of orexinergic cell bodies and fibers within the hypothalamus of broiler chicks was identified using immunohistochemistry for orexin-A and orexin-B. Furthermore, the differences in the hypothalamic orexin mRNA concentrations during the day-night cycle and in feed and food restricted conditions were tested in broiler and layer chicks using RT-PCR. Orexin-ir neurons were showed in a hypothalamic paraventricular population that expands to the stratum cellulare externum. Orexin-ir fibers were seen in the all hypothalamus mainly located in periventicular and basal position. They were distributed between the immunopositive cells bath also intermingled between the immunonegative cells belonging to the n. magnocellularis preopticus, the n. supraopticus ventralis, the n. preopticus periventricularis, the nucleus suprachiasmaticus, the regio lateralis hypothalamus and surrounding the anterior commissure, the pallial commissure and throughout the infundibular region in the n. inferior hypothalami and n. infundibuli. In particular, orexins in the suprachiasmatic nucleus suggest that these peptides may have a role in the suprachiasmatic neuronal activity as demonstrated in other mammalian and non-mammalian species. For the first time orexin-ir fibers were seen in the anterior and posterior median eminence of chick. Here, they are located both in the zona interna and zona externa where they are close apposed to vessels of the portal vasculature. This suggests that orexins may be released in the portal circulation and may have influence on biosynthesis or the secretion of anterior lobe hormones as well as in mammals. No influence of day-night cycle on the expression of hypothalamic orexin mRNA was observed. Quantification of hypothalamic orexin-mRNA expression by real-time RT-PCR shown layer chicks tended to express higher orexin mRNA compared to broiler chicks so, the gene related to orexin neuropeptides is impacted by the genetic selection practices and may play a role in breed-specific body weight setpoint regulation in the chicken The demonstration of increased hypothalamic orexin gene expression after food restriction in broiler probably reflect the involvement of orexins in mechanisms of adaptation to fluctuations in food availability to which the animals are submitted in their natural environment. In summary, our anatomical and physiological results have furthered our understanding of orexin circuit in the neuroendocrine regulation in the hypothalamo-hypophysial tract and in the control of several autonomic functions and behavior. Our findings don’t support the involvement of orexins neither in sleep/wake cycle nor in food intake directly but rather in the linking energy balance and arousal.
Solo per gli Amministratori dell'archivio: edita il record