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Kainate receptor-mediated presynaptic inhibition at the mouse hippocampal mossy fibre synapse
1. The presynaptic action of kainate (KA) receptor activation at the mossy fibre-CA3 synapse was examined using fluorescence measurement of presynaptic Ca(2+) influx as well as electrophysiological recordings in mouse hippocampal slices. 2. Bath application of a low concentration (0·2 μM) of KA reve...
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| Main Authors: | , |
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| Formato: | Artigo |
| Idioma: | English |
| Publicado em: |
Blackwell Science Inc
2000
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| Assuntos: | |
| Acesso em linha: | https://ncbi.nlm.nih.gov/pmc/articles/PMC2269840/ https://ncbi.nlm.nih.gov/pubmed/10718745 https://ncbi.nlm.nih.govhttp://dx.doi.org/10.1111/j.1469-7793.2000.t01-1-00653.x |
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| Resumo: | 1. The presynaptic action of kainate (KA) receptor activation at the mossy fibre-CA3 synapse was examined using fluorescence measurement of presynaptic Ca(2+) influx as well as electrophysiological recordings in mouse hippocampal slices. 2. Bath application of a low concentration (0·2 μM) of KA reversibly increased the amplitude of presynaptic volley evoked by stimulation of mossy fibres to 146 ± 6 % of control (n = 6), whereas it reduced the field excitatory postsynaptic potential (EPSPs) to 30 ± 4 %. 3. The potentiating effect of KA on the presynaptic volleys was also observed in Ca(2+)-free solution, and was partly antagonized by (2S,4R)-4-methylglutamic acid (SYM 2081, 1 μM), which selectively desensitizes KA receptors. 4. The antidromic population spike of dentate granule cells evoked by stimulation of mossy fibres was increased by application of 0·2 μM KA to 160 ± 10 % of control (n = 6). Whole-cell current-clamp recordings revealed that the stimulus threshold for generating antidromic spikes recorded from a single granule cell was lowered by KA application. 5. Application of KA (0·2 μM) suppressed presynaptic Ca(2+) influx to 78 ± 4 % of control (n = 6), whereas the amplitude of the presynaptic volley was increased. 6. KA at 0·2 μM reversibly suppressed excitatory postsynaptic currents (EPSCs) evoked by mossy fibre simulation to 38 ± 9 % of control (n = 5). 7. These results suggest that KA receptor activation enhances the excitability of mossy fibres, probably via axonal depolarization, and reduces action potential-induced Ca(2+) influx, thereby inhibiting mossy fibre EPSCs presynaptically. This novel presynaptic inhibitory action of KA at the mossy fibre-CA3 synapse may regulate the excitability of highly interconnected CA3 networks. |
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