| dc.contributor.author | de Groot, Marleen H. M. | en_US |
| dc.date.accessioned | 2014-10-21T12:38:49Z | |
| dc.date.available | 2004 | |
| dc.date.issued | 2004 | en_US |
| dc.identifier.other | AAINQ89800 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/54606 | |
| dc.description | The studies presented in this thesis were designed to investigate the effects of daily restricted feeding schedules on behavior and gene expression patterns in the brains of mice (Mus musculus). Animals maintained on a restricted feeding schedule in which a single meal is provided at the same time each day will, within a few days, show increased activity and arousal during the hours immediately preceding mealtime. This increase in activity (known as food-anticipatory activity or FAA) will appear even if mealtime occurs at a time of day that the animal is normally at rest and normally does not consume food. Restricted daily access to food can entrain an endogenous, self-sustaining circadian pacemaker that is separate from the light-entrainable pacemaker in the rodent suprachiasmatic nucleus (SCN). The identity of this food-entrainable pacemaker and the nature of the afferent signals that affect it are not known, despite a large number of studies aimed at identifying the critical substrate and signal involved. | en_US |
| dc.description | The intense activity associated with food anticipation is probably mediated by mechanisms that normally arouse animals in order to increase the probability of finding and eating food. At the same time, anticipation probably helps prepare the digestive system for the meal. Recently, a pair of neuropeptides (orexin A and B, also known as hypocretin 1 and 2) was described which have been shown to play a role in sleep, arousal and feeding. Because an animal exposed to a restricted feeding schedule needs to be awake, aroused and prepared to ingest food during the limited daily window of food availability, the functioning of the orexin system is likely altered under conditions of food entrainment. | en_US |
| dc.description | A series of studies were designed in order to investigate this possibility. The first characterized the normal circadian pattern of feeding in C57BL/6J mice and assessed their ability to generate FAA under a restricted feeding schedule (Chapter 2). Results show that mice, that normally exhibit nocturnal feeding patterns, are able to adapt to a restricted feeding schedule in which food is presented daily during the middle of the light phase. The second study investigated strain differences in the distribution of cell bodies containing orexin A and B in the brains of mice (Chapter 3). Orexin immunoreactive cell bodies were found outside of the lateral hypothalamic/perifornical region in all three strains of mice. Although only slight strain differences were found, substantial differences in distribution pattern were found between orexin A and B. The third study included several experiments designed to assess the response of the lateral hypothalamic orexin system to scheduled restricted feeding (Chapter 4). Results show that immediate-early gene expression within the lateral hypothalamus and within orexin-containing cells is altered in animals exposed to chronic restricted feeding. Furthermore, orexin mRNA expression is up-regulated in animals anticipating the arrival of their daily meal. The fourth and final study assessed immediate-early gene expression within brain structures receiving orexin input under conditions of restricted feeding (Chapter 5). It was found that chronic exposure to a restricted feeding schedule not only alters an animal's behavior and physiology, but also substantially modifies patterns of immediate-early gene expression in various brain structures. Furthermore, like behavior and physiology, it appears that altered gene expression patterns emerge after only a few days of exposure to the restricted feeding schedule. The results, their implications and future directions are discussed in Chapter 6. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2004. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Molecular. | en_US |
| dc.subject | Biology, Neuroscience. | en_US |
| dc.title | Entrainment of circadian rhythms in mice by daily bouts of food availability: Analysis of neural gene expression patterns. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
