Mossy fibers

Rat (Wistar) 3 wk 7 d/wk ad lib (W) 15 (increase in volume of mossy fiber zone, granule cell layer, and commissural association zone in hippocampus of offspring) Slomianka et al. 1989 PbAc... 

Alfano DP, LeBoutillier JC, Petit TL. 1982. Hippocampal mossy fiber pathway development in normal and postnatally lead-exposed rats. Exp Neurol 75 308-319. 

Yokoi, M., Kobayashi, K., Manabe, T. et al. Impairment of hippocampal mossy fiber LTD in mice lacking mGluR2. Science 273 645-647,1996. 

Villacres, E., Wong, S. T., Chavkin, C. and Storm, D. R. Type I adenylyl cyclase mutant mice have impaired mossy fiber long-term potentiation. /. Neurosci. 18 3186-3194,1998. 

Longo, B. M. and Mello, L. E. Supragranular mossy fiber sprouting is not necessary for spontaneous seizures in the intrahippocampal kainate model of epilepsy in the rat. Epilepsy Res. 32 172-182,1998. 

Nadler, J. V. The recurrent mossy fiber pathway of the epileptic brain. Neurochem. Res. 28 1649-1658, 2003. 

CA3 pyramidal neurons receive the mossy fiber input from the granule neurons of the dentate gyrus. This connection is part of the 3-cell circuit of the hippocampus that is believed to be involved in learning and memory. 

A second type of NMDA-receptor-independent LTP exists in the mossy-fiber pathway at the dentate granule cell-to-CA3 pyramidal cell synapse [19]. This form of LTP, termed mossy fiber-CA3 LTP, is believed to involve PKA activation in the presynaptic cell which leads to increased neurotransmitter release. However, the exact induction mechanism is not yet clear. 

There is growing evidence to suggest that, within the hippocampus, kainate and AIPA may depress fast excitatory transmission by distinct mechanisms. For example, in area CA3, kainate exerts its effects via an action on presynaptic mossy-fiber excitability (37,92), whereas ATPA is suggested to act indirectly via an increase in... 

Kainate (200 nM) renders the mossy-fiber axons more excitable, as evidenced by an increase in the presynaptic fiber volley as well as lowered threshold for antidromic action potentials. At the same time, a kainate-induced suppression of synaptic transmission and depression of presynaptic calcium influx was observed (92). In contrast, application of very low concentrations of kainate (50 nM) facilitates synaptic transmission at the mossy fibers (77,100). The kainate-induced facilitation is blocked by LY382884, suggesting a role for GLUK5-containing receptors (77). However, only depression of transmission has been observed with ATPA (35). Thus, the facilitatory and depressory effects of kainate could be mediated by different receptor populations that have distinct pharmacological properties. 

The recently developed GLUK5 selective compound LY382884 (47) is the first antagonist that is selective enough for kainate receptors over AMPA receptors to be used to study the functions of native KA receptors in the presence of intact AMPA receptor-mediated transmission. The use of LY382884 has uncovered a role for kainate receptors in the regulation of short- and long-term synaptic plasticity in the mossy-fiber pathway (49,77) as well as at thalamocortical synapses (87) (Fig. 3)... 

Kainate receptors have recently been implicated in the induction of EIP in the mossy fibers (49,85). Unlike EIP in the area CA1, induction of mossy-fiber EIP is independent of NMDA-receptor activation and involves presynaptic mechanisms (105). Synaptic activation of the facilitatory presynaptic receptor can account for the role of KA receptors in the induction of mossy-fiber LIP by maintaining a high level of release during high-frequency transmission (77). Furthermore, following induction of LTP, the presynaptic kainate receptor-mediated facilitation of synaptic transmission is lost, suggesting that the mechanism by which presynaptic kainate receptors facilitate... 

Schmitz, D., Frerking, M., and Nicoll, R. A. (2000) Synaptic activation of presynaptic kainate receptors on hippocampal mossy fiber synapses. Neuron 27,327-338. 

Contractor, A., Swanson, G., and Heinemann, S. F. (2001) Kainate receptors are involved in short- and long-term plasticity at mossy fiber synapses in the hippocampus. Neuron 29, 209-216. 

Chronic treatment with EGb 761 in mice created histological changes in the hippocampus (Barkats et al. 1995). Increases are seen in the projection field of hippocampal mossy fibers and a reduction in the area of the stratum radiatum. These changes are hypothesized to result from... 

Sharma G, Ajayaraghavan S (2003) Modulation of presynaptic store calcium induces release of glutamate and postsynaptic firing. Neuron 38 929-939 Sharma G, Grybko M, Vijayaraghavan S (2008) Action potential-independent and nicotinic receptor-mediated concerted release of multiple quanta at hippocampal CA3-mossy fiber synapses. J Neurosci 28 2563-2575... 

Huag T, Storm JF (2000) Protein kinase A mediates the modulation of the slow Ca2+-dependent K+ current, lsAHP,by the neuropeptides CRF, VIP, and CGRP in hippocampal pyramidal neurons. J Neurophysiol 83 2071-2079 Huang Y, Li X-C, Kandel ER (1994) cAMP contributes to mossy fiber LTP by initiating both a covalently mediated early phase and macromolecular synthesis-dependent late phase. Cell 79 69-79... 

Vaidya V.A., Siuciak J.A., Du E, and Duman R.S. (1999) Hippocampal mossy fiber sprouting induced by chronic electroconvulsive seizures. Neuroscience 89 157—166. 

The parallel fibers receive input from many sources via a complex series of mossy fibers and granule cells and influence the firing of the Punkinje cells. The output from the Purkinje cells is entirely inhibitory. It is transmitted via synapses in the cerebellar nuclei to neurons that lead back to the cerebral cortex, into the thalamus, and down the spinal cord.411 The pathway to the cortex completes an inhibitory feedback loop, of which there are many in the nervous system. For details see Llinas404 and Nicholls.149... 

Rebola N, Lujan R, Cunha RA, Mulle C (2008) Adenosine A2A receptors are essential for long-term potentiation of NMDA-EPSCs at hippocampal mossy fiber synapses. Neuron 57(1) 121—134... 

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