EXPOSURE TO PREDATOR ODOR REDUCES LOCOMOTOR-ACTIVITY LEVELS IN ADULT MALE-RATS - LACK OF EFFECT OF HIPPOCAMPAL LESION

The hippocampus has been implicated in mediating responses to predator s. Involvement of the hippocampus was tested in the present study in w hich a multivariate analysis of the locomotor activity of intact and h ippo-campectomized (destruction of dentate and CA1 cells) laboratory r ats, Rattus norvegicus, was conducted following exposure to a predator odor. Levels of various activity variables were monitored in an autom ated activity monitoring system following a brief 3-min exposure to 2- propylthietane (weasel odor), caproic acid (goat odor), toluene (organ ic solvent), and a no-odor condition in hippocampal-lesioned (using co lchicine) and sham-operated control male rats. Rats of both groups dis played reduced levels of total distance, movement time, vertical activ ity, and number of movements following exposure to weasel odor and tol uene in comparison to the no-odor condition. Exposure to goat odor res ulted only in reduced levels of vertical activity and number of moveme nts. There were no differences in activity levels between hippocampal- lesioned and sham-operated rats during baseline activity recording or follow ing exposure to any of the odors. However, hippocampal-lesioned rats spent less time in the center of the activity boxes than sham-op erated control rats across all conditions. This study demonstrates tha t laboratory rats show marked changes in locomotion in response to the odor of a predator and suggests that an intact hippocampus is not ess ential for mediating these responses.