PRENATAL PROTEIN-MALNUTRITION EFFECTS ON THE SEROTONERGIC SYSTEM IN THE HIPPOCAMPAL-FORMATION - AN IMMUNOCYTOCHEMICAL, LIGAND-BINDING, AND NEUROCHEMICAL STUDY

Prenatally protein malnourished rats born to dams maintained on a 6% c asein diet during pregnancy and then fostered at birth to females on a 25% casein diet show adult alterations in hippocampal kindling and lo ngterm potentiation and behavioral changes that all suggest dysfunctio n of hippocampal formation (HF). In the present investigation, compare d to well-nourished controls, 220 day malnourished rats exhibited a de crease in the 5-HT fiber density in the dentate gyrus (DG) and CA3 sub field and, a 15-25% decrease 5-HT uptake sites assayed with [H-3]-cita lopram in CA3 and CA1. In malnourished rats, 5-HT1A receptors assayed with [H-3]8-OH-DPAT were decreased by 20% in CA3. Because most hippoca mpal subfelds showed no 5-HT changes, hippocampal 5-HT levels determin ed via HPLC methods were similar in adult malnourished and control rat s. These results suggest that there are localized changes in the 5-HT afferent system in the hippocampal formation of the 220 day prenatally protein malnourished rat. Considering the 5-HT afferent input to inhi bitory intrahippocampal neurons, the decreased 5-HT plexus may result in increased inhibition within specific hippocampal subfields despite overall normal levels of 5-HT in the total HF.