Psychoemotional manifestations in hippocampectomized rats

The effects of lesioning of the dorsal hippocampus on the psychoemotional state of Wistar rats were studied. Hippocampal lesions did not affect the learning process, but affected mainly the pattern of psychoemotional manifestations in all animals regardless of the typology of higher nervous activity. All animals showed reductions in the extremes of types of passive and active stress reactions. Individual effects depended on the behavioral phenotypes of the animals. Hippocampal lesions in rapidly learning rats (10%) led to sharp decreases in irritability (active/passive = 0.35/0.5 instead of 1.0/0.4), while passive-defensive manifestations were not altered. In slowly learning animals (30%), hippocampal lesions were not accompanied by qualitative changes in the patterns of psychoemotional manifestations, while non-learning rats (60%) showed decreases in passive and increases in active manifestations (active/passive = 0.45/1.4 instead of 0.3/1.9). It is suggested that the hippocampus is involved in producing psychoemotional reactions, individual patterns of which depend on the morphofunctional characteristics of the system responsible for organizing the psychoemotional state.Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 89, No. 7, pp. 868–878, July, 2003.