Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
Victor de Valaming
Robert H. Fitts
In teleosts, as in most other vertebrates, the neuroendocrine system closely integrates various factors from the external and internal environments so as to permit specific physiological modifications as they are needed. Clearly, the timing of certain biological phenomena, especially reproduction, migration, fat deposition, with appropriate environmental conditions is of considerable adaptive value. In seasonally active fish, many factors are utilized as cues for the Initiation of relevant physiological activities, including temperature, photoperiod and nutrition as well as salinity, rainfall and pheromones in some species. In many instances, photoperiod and temperatures are major controlling environmental factors.
Little attention has been given to the neuroendocrine mechanism which might mediate the various physiological responses to changing environmental conditions. It seems likely that fish employ similar, although not necessarily identical mechanisms as in mammals, to which the majority of neuroendocrine research has been devoted. For example, it may be realized that brain monoamines play a role in the control of hypophysiotropic factors in both vertebrate classes, and yet the specific nature and degree of control may be quite distinct. Also, it may be found that endocrine feedbacks to the monoarninergic system in the brains of both fish and mammals are present, but it is unlikely that all of the same hormones will be involved, since there are obvious differences in the endocrinology of these groups.
With these potential differences in mind, it was my desire to investigate the nature of the hypothalamic monoaminergic system in the cyprinid teleost Carassius auratus, a commonly utilized fish in physiological studies. The goal of my research has been to define the role of the enzyme monoamine oxidase in the aminergic system of the goldfish hypothalamus, particularly under conditions of changing photoperiod and temperature . It is believed that studies of this kind can contribute vital information of both general and comparative interest to the understanding of hypothalamo-hypophysial interactions in nonmammalian species .