Publication Date


Document Type


First Advisor

Conway, Sonya

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Somatotropin; Sex (Biology)


The regulation of the sexual dimorphic pattern of growth hormone (GH) secretion between the male and female rat was studied by examining GH autofeedback characteristics. The model used was the capacity of Intraventricularly (ivt) administered oGH to suppress a GH surge induced by clonidine (CLON). Studies were undertaken in male and female rats under varying diurnal, gonadal hormone, and hypothalamic hormone conditions. These studies demonstrated that normal or adult ovariectomized (OVXed) female rats are less sensitive to CLON stimulation and ivt oGH inhibition of GH secretion than males or prepubescent OVX females. In addition, exposure to ovarian hormones at puberty may be important in establishing the difference in timing and amplitude of GH surges in male and female rats. Female rats may have a stronger SRIF inhibition of GRH release than males. Testosterone may not directly affect CLON sensitivity or GH feedback, but may influence the male pattern of secretion at a site preceding alpha-2-adrenergic neurons. Further, there may be diurnal variation in the control of GH secretion in the female. Finally, these results support a role for GRH in GH negative feedback system.


Includes bibliographical references (pages 116-134)


ix, 167 pages




Northern Illinois University

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