Firing Mode-Dependent Synaptic Plasticity in Rat Neocortical Pyramidal Neurons

B. Birtoli
2004 Journal of Neuroscience  
Pyramidal cells in the mammalian neocortex can emit action potentials either as series of individual spikes or as distinct clusters of high-frequency bursts. However, why two different firing modes exist is largely unknown. In this study, we report that in layer V pyramidal cells of the rat somatosensory cortex, in vitro associations of EPSPs with spike bursts delayed by ϩ10 msec led to long-term synaptic depression (LTD), whereas pairings with individual action potentials at the same delay
more » ... ced long-term potentiation. EPSPs were evoked extracellularly in layer II-III and recorded intracellularly in layer V neurons with the whole-cell or nystatin-based perforated patch-clamp technique. Bursts were evoked with brief somatic current injections, resulting in three to four action potentials with interspike frequencies of ϳ200 Hz, characteristic of intrinsic burst firing. Burst-firing-associated LTD (Burst-LTD) was robust over a wide range of intervals between Ϫ100 and ϩ200 msec, and depression was maximal (ϳ50%) for closely spaced presynaptic and postsynaptic events. Burst-LTD was associative and required concomitant activation of low voltage-activated calcium currents and metabotropic glutamate receptors. Conversely, burst-LTD was resistant to blockade of NMDA receptors or inhibitory synaptic potentials. Burst-LTD was also inducible at already potentiated synapses. We conclude that intrinsic burst firing represents a signal for resetting excitatory synaptic weights.
doi:10.1523/jneurosci.0795-04.2004 pmid:15163685 fatcat:y6bjwpnwj5drblzr4wejpby2bi