Summer Undergraduate Diversity Program

National Science Foundation
Experimental Program to
Stimulate Competitive Research

Summer Undergraduate Diversity Research Program

Michel Lau
Faculty Advisor
Dr. Craig Johnston
Department of Pharmaceutical Sciences

Changes in Central Oxytrocin Receptors
in Relation to the Preovlatory Surge of
Luteinizing Hormone in Cycling Female Rats

Abstract

Oxytocin (OT) has been shown to exert a physiologically relevant stimulatory influence on the preovulatory surge of luteinizing hormone (LH), which causes ovulation. Further studies demonstrate that this stimulation is mediated via oxytocin receptors (OT-R), but where and how OT-R influence LH secretion is not known. Using immunocytochemical methods the present study investigated changes in OT-R which occur throughout the day of proestrus in the cycling female Sprague-Dawley rat to determine the location and mechanisms by which OT-R affect the proestrous surge of LH. Cycles of rats were determined by changes in vaginal cytology obtained by daily vaginal lavage. Regular cycling proestrous animals were perfused under tribromoethanol anesthesia at 9:00 hr, 16:00 hr and at 20:00 hr to compare the location and quantity of OT-R throughout the hypothalamus. These times were chosen because previous data showed that OT-R message expression increased by fifteen fold between 9:00 hr and 15:00 hr on proesterus. Both immunoperoxidase staining with DAB and immunofluorescent staining with secondary antibody conjugated to Texas Red or Alexa red fluorescent probe were used at concentrations determined by titration on 10-20 micron frozen sections of the rat hypothalamus to visualize the OT-R. Both techniques were used in order to determine which method would provide a more reliable technique for analysis. Antibody concentrations have been determined and the analysis of brain slices obtained at all three times has now begun.