Nancy S. Morrow, Ph.D.
Advisor: Dr. Stephen Kiefer
Investigation of running and gastric ulceration in the rat during activity stress
The impetus behind the self-destructive wheel running that occurs in activity-stress was explored in a series of experiments. The first experiment used surface recordings from the stomach (the electrogastrogram) to examine the relationship between changes in gastric function and increased wheel running. Results indicated that changes in the frequency and amplitude of stomach potentials were accompanied by increased activity and gastric ulceration. Home cage control rats did not exhibit changes in the EGG and did not become ulcerated. It was suggested that changes in gastric factors influenced the development of excessive wheel running.
The next two experiments investigated the role of norepinephrine (NE) in triggering excessive wheel running during restricted feeding. Injections of FLA-63, a NE antagonist, were given (ip) during the 7 h period before or after the feeding session; saline was injected into activity controls. Results indicated that rats injected prior to the feeding hour ran less than their saline counterparts throughout the entire day, had reduced ulceration, but did not have an increased liklihood of survival. Rats injected after the feeding hour decreased running only during the interval of drug treatment while running similar amounts as the saline controls during the hours preceding the feeding hour; there were no significant differences in ulcer severity between rats injected with saline or FLA-63 during the postfeeding hours. It was speculated that NE contributed to excessive running during restricted feeding but that adequate stores of NE were necessary for survival during activity-stress.
The running patterns between males and females were also examined. Results indicated that both males and females increased running in a similar manner but that females ran more than males during baseline conditions and throughout testing. The estrous cycle in female rats did not impose an estrous-related peak in activity. It was suggested that using females during activity-stress procedures may have both practical and theoretical advantages.
Ph.D., Psychology, Kansas State University, 1989