Evidence against AMPA Receptor-Lacking Glutamatergic Synapses in the Superficial Dorsal Horn of the Rat Spinal Cord (original) (raw)
2009, Journal of Neuroscience
Pure NMDA receptor (NMDAr)-mediated EPSCs, thought to correspond to "silent" glutamatergic synapses that lack AMPA receptors (AMPArs), have been observed in superficial spinal dorsal horn of neonatal but not adult rats. Recent anatomical studies suggest that AMPArs are present at virtually all glutamatergic synapses in this region in adults. We used antigen retrieval to examine co-localisation of AMPArs and PSD-95 (a marker for glutamatergic synapses) in laminae I-II of neonatal and adult rats. We found a high degree of co-localisation in all cases, which suggests that AMPArs are present in the great majority of glutamatergic synapses even in neonatal animals. We therefore re-examined evidence for silent synapses by performing blind whole-cell recordings from superficial dorsal horn neurons in slices from neonatal or adult rats, with focal stimulation to activate glutamatergic synapses. On some occasions in both neonatal (10/109, 9%) and adult (9/77, 12%) slices NMDAr-mediated EPSCs were observed when the holding potential was raised to +50mV at a stimulus strength that had failed to evoke AMPAr-mediated EPSCs. However, in all cases tested, AMPAr-mediated EPSCs were then observed when the cell was returned to −70 mV; this and other properties of the EPSCs suggest that they do not represent genuine silent synapses. When compared with previous findings, our results indicate that the appearance of silent synapses depends on experimental protocol. This suggests that pure NMDAr-mediated EPSCs seen in previous studies do not correspond to AMPAr-lacking synapses, but result from another mechanism, for example loss of labile AMPArs from recently formed synapses.
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.