In this review we have assessed the effects of prenatal protein malnutrition on the hippocampal formation of the developing brain. In investigating this insult in the hippocampal neuronal model we have concentrated on aspects of enhanced inhibition we have shown in our earlier studies. Since this involves particular attention to the GABAergic interneurons we have examined the complex interneuronal networks of the hippocampal formation and their neurotransmitter afferent inputs, particularly the serotonergic system from the midbrain raphé nuclei. A variety of combinations of specialized interneurons are discussed in terms of how malnutrition insults perturb function in these inhibitory and disinhibitory networks. Pathological enhancement of inhibition manifests itself by diminished plasticity, alterations in theta activity and deficits in long-term learning behaviors. Long-term inhibition in select GABA interneuron systems may form a major derangement seen following prenatal protein malnutrition. The focus of this study is to relate enhanced inhibition to the several forms of inhibitory systems present in the hippocampal formation and develop hypotheses as to the primary derangements that may account for pathological inhibition in prenatal malnutrition.