A Critical Window for Experience-Dependent Plasticity at Whisker Sensory Relay Synapse in the Thalamus

Abstract

This study investigated the role of sensory experience in the refinement of whisker sensory relay synapses in the ventral posterior medial nucleus (VPm) of the murine thalamus. Sensory deprivation was done by whisker plucking, and synaptic connectivity was determined by whole-cell patch-clamp recording in acute slices. Sensory deprivation started at P12-P13, but not at P16, disrupted the elimination of VPm relay synapses. The majority of deprived neurons received multiple relay inputs, whereas the majority of nondeprived neurons received a single relay input. Sensory deprivation started a few days earlier at P10, however, had no effect on synapse elimination. The disruption of synapse elimination was associated with a delay in synapse maturation. The AMPA/NMDA ratio of EPSC was significantly smaller in deprived neurons. On the other hand, deprivation had no effect on the peak amplitude or decay time constant of the NMDA component, or the I-V relationship of the AMPA component, nor does it affect the paired-pulse ratio of EPSCs. The reduction in the AMPA/NMDA ratio was already evident within 24 h of whisker plucking, and the effect is associated with a reduction in the amplitude of quantal AMPA events. Thus, P12-P13 is a critical period for experience-dependent refinement at the whisker sensory relay synapse in the VPm.

Rewiring of Afferent Fibers in the Somatosensory Thalamus of Mice Caused by Peripheral Sensory Nerve Transection

“…To determine the number of lemniscal inputs for each relay neuron, we recorded evoked lemniscal EPSCs at holding potentials of Ϫ70 and ϩ40 mV from the same cell over a wide range of stimulus intensity (typically from 10 to 400 A) (Arsenault and Zhang, 2006;Chen, 2006, 2008;Wang and Zhang, 2008). First, we roughly searched for EPSC steps using the increment of 50 A.…”

“…Liquid junction potential was compensated (estimated as ϩ13 mV). The rectification index was defined as the ratio of the EPSC amplitude at ϩ40 mV to that at Ϫ40 mV (Isa et al, 1995;Wang and Zhang, 2008).…”

“…To analyze input-specific miniature EPSCs, we recorded Sr 2ϩ -induced delayed miniature EPSCs (Wang and Zhang, 2008). First, single-fiber-mediated lemniscal EPSCs were recorded in the presence of 100 M DL-APV.…”

“…1 B, C). One week after the IONC, we assessed the number of lemniscal fiber inputs to a single relay neuron by step-counting procedures, as previously described (Arsenault and Zhang, 2006;Wang and Zhang, 2008). We counted the number of EPSC steps with an increase of stimulus intensity (see Materials and Methods).…”

Peripheral nerve damage does not alter release properties of developing central trigeminal afferents

“…The Pr value has been used to identify the first order relays and higher order relays in the thalamus (Reichova and Sherman 2004;Sherman 2007). In the trigeminal pathway, the higher relay stations [the ventral posterior medial nucleus (VPM) of the thalamus and layer IV excitatory neurons in the barrel cortex] exclusively receive high Pr terminals that result in paired-pulse depression (PPD) (Castro-Alamancos 2002;Laurent et al 2002;Deschenes et al 2003;Yanagisawa et al 2004;Fontanez and Porter 2006;Lu et al 2006;Iwasato et al 2008;Lee and Sherman 2008;Wang and Zhang 2008;Zhu 2009). However, the properties of afferent terminals in the PrV have not been investigated.…”