EFFECTS OF PRENATAL PROTEIN-MALNUTRITION ON HIPPOCAMPAL LONG-TERM POTENTIATION IN FREELY MOVING RATS

It has been demonstrated that prenatal protein malnutrition significan tly affects hippocampal plasticity, as measured by long-term potentiat ion, throughout development. This paper focuses on the hippocampal den tate granule cell population response to two separate paradigms of tet anization of the medial perforant pathway in prenatally protein-malnou rished and normally nourished adult male rats, The 100-pulse paradigm consisted of the application of ten 25-ms-duration bursts of 400 Hz st imulation with an interburst interval of 10 s. The 1000-pulse paradigm consisted of the application of five 500-ms bursts of 400 Hz stimulat ion with an interburst interval of 5 s. No between-group differences w ere obtained for input/output response measures prior to tetanization. No between-group, nor between-paradigm, differences were obtained in the degree of population EPSP slope enhancement, However, in response to both paradigms, prenatally malnourished animals showed significantl y less enhancement of the population spike amplitude (PSA) measure tha n normally nourished animals, Normally nourished animals showed a sign ificantly greater level of PSA enhancement in response to the 100-puls e paradigm than the 1000-pulse paradigm, Prenatally malnourished anima ls showed no significant differences in the degree of PSA enhancement between the two paradigms, Results indicate that short duration bursts (less than or equal to 25 ms) are more effective in inducing maximal PSA enhancement in normally nourished rats than longer duration stimul us bursts. The apparent inability of prenatally malnourished rats to t ransfer enhanced cellular activation (population EPSP slope enhancemen t) into enhanced cellular discharge (PSA enhancement) suggests that a preferential enhancement of GABAergic inhibitory modulation of granule cell excitability may result from the prenatal dietary insult. Such p otentiation of inhibitory activity would significantly lower the proba bility of granule cell population discharge, resulting in the signific antly lower level of PSA enhancement obtained from these animals, (C) 1997 Academic Press.