Neuroscience 2005 Abstract
| Presentation Number: | 985.20 |
|---|---|
| Abstract Title: | Effects of a representational border on inhibitory synapses in adult rat primary somatosensory cortex (S1). |
| Authors: |
Hickmott, P. W.*1,2
1Dept Psychol, Univ. of California, Riverside, CA 2Interdepartmental Neurosci. Program, Univ. of California, Riverside, CA |
| Primary Theme and Topics |
Sensory and Motor Systems - Tactile/Somatosensory -- Thalamus and Cortex |
| Session: |
985. Tactile/Somatosensory: Thalamus and Cortex V Poster |
| Presentation Time: | Wednesday, November 16, 2005 4:00 PM-5:00 PM |
| Location: | Washington Convention Center - Hall A-C, Board # EE20 |
| Keywords: | barrel cortex, cortical plasticity, IPSPs, synaptic plasticity |
In rat S1, stimulation of connections that stay within a representation (NCB) yields inhibitory responses (IPSPs) that are larger than those evoked by stimulation of connections that cross into an adjacent representation (CB; Hickmott & Merzenich, 1997). Such differences may reflect the fact that there are fewer axons that cross a representational border than project within a representation (Mason et al, SFN Abstr. 2003). In this abstract we investigated whether inhibitory synapses have different properties between NCB connections and CB connections.
The border between the forepaw and lower jaw representations was mapped in adult rats (>P90) using in vivo recording and marked with DiI. Coronal slices were taken from the marked region and maintained in vitro. Whole-cell recordings were obtained from layer 2/3 neurons close to the border. Filling solution with a high concentration of chloride (100 mM) was used to enhance IPSP amplitude. Horizontal connections within layer 2/3 were electrically stimulated; stimuli were either at a site that was across the border from the neuron (CB) or at an equivalent site within the representation (NCB). IPSPs were isolated by bath application of 10 µM CNQX plus 100 µM APV. The synaptic efficacies of IPSPs were estimated by using minimal stimulation of CB and NCB connections. The mean minimal IPSP amplitudes (n=5) were .53±.11 mV for CB and .55±.15 mV for NCB. The short-term dynamics of IPSPs were also examined by stimulating CB and NCB connections with short trains of stimuli at various frequencies (5-20 Hz). IPSPs from CB and NCB stimulation exhibited different falling time dynamics and steady-state amplitudes during these trains (n=3). These data suggest that the synaptic efficacies IPSPs are similar between CB and NCB connections, but that there are differences in their short-term dynamics. Thus, a representational border can affect the properties of inhibitory synapses.
The border between the forepaw and lower jaw representations was mapped in adult rats (>P90) using in vivo recording and marked with DiI. Coronal slices were taken from the marked region and maintained in vitro. Whole-cell recordings were obtained from layer 2/3 neurons close to the border. Filling solution with a high concentration of chloride (100 mM) was used to enhance IPSP amplitude. Horizontal connections within layer 2/3 were electrically stimulated; stimuli were either at a site that was across the border from the neuron (CB) or at an equivalent site within the representation (NCB). IPSPs were isolated by bath application of 10 µM CNQX plus 100 µM APV. The synaptic efficacies of IPSPs were estimated by using minimal stimulation of CB and NCB connections. The mean minimal IPSP amplitudes (n=5) were .53±.11 mV for CB and .55±.15 mV for NCB. The short-term dynamics of IPSPs were also examined by stimulating CB and NCB connections with short trains of stimuli at various frequencies (5-20 Hz). IPSPs from CB and NCB stimulation exhibited different falling time dynamics and steady-state amplitudes during these trains (n=3). These data suggest that the synaptic efficacies IPSPs are similar between CB and NCB connections, but that there are differences in their short-term dynamics. Thus, a representational border can affect the properties of inhibitory synapses.
Supported by NINDS NS42241
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
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