Lesions of parvocellular subdivisions of the hypothalamic paraventricular nucleus alter open field behavior and acquisition of sensory and spatial discrimination

Abstract

Rats with ibotenic acid (IBO) lesions of the hypothalamic paraventricular nucleus (PVN) were compared with operated control animals over a battery of tests designed to assess memory- and arousal-related behavioral processes. At the dose employed in these experiments, ibotenic acid selectively destroys parvocellular elements of the PVN, leaving magnocellular subdivisions relatively intact, allowing for experimental dissection of the influence of parvocellular and magnocellular PVN neuronal populations on the behavioral parameters measured. IBO-treated rats showed a greater incidence ofrearing behavior and exhibited greater levels of total and central ambulation in an open field than control rats. Acquisition of both sensory and spatial reward contingencies were retarded in the IBO-lesion group; however, no differences were evident between IBO-treated and control groups in an approach-avoidance test, nor in the ability to perform the spatial and sensory discrimination tasks to a criterion level of accuracy. Histological examination verified that bilateral IBO lesion destroyed parvocellular elements of the PVN, while sparing the majority of magnecellular neurons. Results suggest that parvocellular PVN lesion alter behavioral performance via interactions with physiological systems overning arousal level.