When CA3 commissural afferents received low-frequency (weak) stimuli synchronized with a train of mossy fiber bursts (strong), associative long-term potentiation (LTP) was induced at mixed commissural and associational synapses on hippocampal CA3 pyramidal cells in vitro. In contrast, a weak mossy fiber input did not potentiate when given in phase with commissural/associational bursts. Furtherm...

A single mossy fiber input contains several release sites and is located on the proximal portion of the apical dendrite of CA3 neurons. It is, therefore, well suited to exert a strong influence on pyramidal cell excitability. Accordingly, the mossy fiber synapse has been referred to as a detonator or teacher synapse in autoassociative network models of the hippocampus. The very low firing rates...

Extensive research has revealed a fundamental organization of the cerebellum consisting of functional parasagittal zones. This compartmentalization has been well documented with respect to physiology, biochemical markers, and climbing fiber afferents. Less is known about the organization of mossy fiber afferents in general, and more specifically in relation to molecular markers such as zebrin. ...

P2X(7) receptor subunits form homomeric ATP-gated, calcium-permeable cation channels. In this study, we used Western blots and immunocytochemistry to demonstrate that P2X(7) receptors are abundant on presynaptic terminals of mossy fiber synapses in the rat hippocampus. P2X(7)-immunoreactive protein was detected using a specific P2X(7) antibody in Western blots of protein isolated from whole hip...

Mossy fiber synapses on hippocampal CA3 pyramidal cells, in addition to expressing an NMDA receptor-independent form of long-term potentiation (LTP), have recently been shown to express a novel presynaptic form of long-term depression (LTD). We have studied the mechanisms underlying mossy fiber LTD and present evidence that it is triggered, at least in part, by a metabotropic glutamate receptor...

Dentate granule cells (DGCs) and their microcircuits have been implicated in hippocampus-dependent memory encoding and epileptogenesis. Little is known about how the proper maturation of DGCs is determined by their intrinsic programs or external factors during development. In order to explore this, we dispersed premature DGCs on living hippocampal slices. Here we report that the survival and ne...

The dentate gyrus is one of two main areas of the mammalian brain where neurons are born throughout adulthood, a phenomenon called postnatal neurogenesis. Most of the neurons that are generated are granule cells (GCs), the major principal cell type in the dentate gyrus. Some adult-born granule cells develop in ectopic locations, such as the dentate hilus. The generation of hilar ectopic granule...

Repeated kindled seizures induce long-lasting physiological and morphological alterations in the hippocampal formation. In the dentate gyrus (DG), the morphological alterations induced by kindled seizures include loss of polymorphic neurons in the hilus, mossy fiber axon sprouting, and synaptic reorganization of the mossy fiber pathway. In this study, quantitative stereological methods were use...

The mossy fiber pathway has long been considered to provide the major source of excitatory input to pyramidal cells of hippocampal area CA3. In this review we describe anatomical and physiological properties of this pathway that challenge this view. We argue that the mossy fiber pathway does not provide the main input to CA3 pyramidal cells, and that the short-term plasticity and amplitude vari...

Commentary Identification and characterization of the vast variety of hippo-campal principal neurons and interneurons are necessary to understand the role that each cell type plays in the complex network alterations leading to epilepsy (1). Over several decades, research has focused on which cells are necessary, sufficient, or extraneous for hippocampal dysfunction often observed in animal mode...