UBC Theses and Dissertations
Systemic epinephrine and defensive burying in the rat Terlecki, Lori Janine
Many investigators have suggested that epinephrine influences the behaviour of organisms in aversive situations; however, attempts to confirm this prediction by examining the effects of adrenal demedullation and epinephrine injections on the performance of rats in traditional aversive conditioning paradigms have failed to provide unambiguous support for this point of view. In the present investigations, the recently developed defensive burying paradigm was used to assess the effects of epinephrine on the behaviour of rats in aversive situations. Defensive burying refers to the fact that rats typically respond to well-defined aversive objects by pushing moveable material towards and over them. Rats with demedullated adrenal glands, and therefore reduced systemic levels of epinephrine, exhibited reduced levels of burying of an unconditioned aversive stimulus (Experiments 5 and 6). This reduction of burying observed in demedullated rats was counteracted by replacement injections of epinephrine (Experiment 6). Intact rats given systemic injections of .01, .1, .5 or 1 mg/kg of epinephrine exhibited increased levels of burying of both unconditioned and conditioned aversive stimuli (Experiments 1, 2, 3, 4, and 6); whereas, a larger dose (2 mg/kg) of epinephrine produced an obvious motor impairment (Experiment 4). These findings clearly confirm the hypothesis of a relation between levels of epinephrine and the responsiveness of organisms to aversive stimulation. Furthermore, the systematic and robust nature of these results illustrates the utility of the defensive burying paradigm in the investigation of epinephrine-behaviour relations and the mechanisms that underlie them.
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