Granule cells NMDA receptors

There have been a number of observations which show increased excitation and/or reduced inhibition in slices prepared from human epileptic brain tissue. Thus burst discharges can be evoked with stimuli that would not do so in normal animal tissue and these can be blocked by NMD A receptor antagonists. The inhibitory postsynaptic currents (IPSCs) in hippocampal dentate granule cells in slices prepared from temporal lobe epileptic tissue are in fact reduced by stimulation that activates NMDA currents (Isokawa 1996), which are more prolonged than usual and show changes in slope conductance. 

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. 

Cehers, G., Cehere, A., Wagner, A., Liljequist, S. (1999). Prolonged inhibition of glutamate reuptake down-regulates NMDA receptor fimctions in cultured cerebellar granule cells. J. Neurochem. 72 2181-90. 

Halabisky B, Friedman D, Radojicic M, Strowbridge BW. 2000. Calcium influx through NMDA receptors directly evokes GABA release in olfactory bulb granule cells. J Neurosci 20 5124-5134. 

Fig. 7. The distribution of the NMDA receptor NRl subunit mRNA splice variants in the adult rat brain (X-ray film autoradiographs, horizontal sections). Pan, NRl total mRNA AV, anteroventral thalamic nuclei Cb, cerebellum Cp, caudate putamen Cx, neocortex Dg, denate granule cells ER, entorhinal cortex Hi, hippocampus S, septum smc, sensori-motor cortex T, thalamus. Scale bar, 1.8. mm (Laurie and Seeburg, 1994). See Fig. 6 for explanation of the nomenclature.

Fig. 14. Expression of the NMDA receptor NR2 subunit mRNAs in the dentate gyrus of the adult rat hippocampus (emulsion autoradiographs). DG, dentate granule cells arrows indicate examples of labelled cells. (Monyer et al., 1992, 1994). Scale bar, 50 p,m.

Vallano ML, Lambolez B, Audinat E, Rossier J (1996) Neuronal activity differentially regulates NMDA receptor subunit expression in cerebellar granule cells. J Neurosci 76 631-639. 

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