Dorsal root potential produced by a TTX-insensitive micro-circuitry in theturtle spinal cord

1. The mechanisms underlying the dorsal root potential (DRP) were studied i n transverse slices of turtle spinal cord. DRPs were evoked by stimulating one filament in a dorsal root and were recorded from another such filament. 2. The DRP evoked at supramaximal stimulus intensity was reduced but not el iminated after blockade of GABA(A) receptors. The remaining component was e liminated by blocking NMDA and AMPA receptors. 3. The DRP was reduced but not eliminated after blockade of AMPA receptors. The early component of the remaining DRP was dependent on GABA(A) receptor s and the residual component on NMDA receptors. 4. The DRP was reduced but not eliminated by TTX. GABA(A), NMDA and AMPA re ceptors contributed to the generation of the TTX-insensitive DRP. The early component of the DRP in the presence of TTX depended on GABA(A) receptor a ctivation, and the late component mainly on the activation of NMDA receptor s. 5. Our results show that part of the DRP is generated by a TTX-resistant, p robably non-spiking micro-circuit with separate components mediated by GABA and glutamate.