Effect of Pregabalin on Synaptic Transmission in Rat Dorsal Horn Ganglion and Dorsal Horn Co-Cultures

The calcium channel alpha-2-delta (α2δ) subunit is an auxiliary subunit associated with voltage-dependent calcium channels, and is implicated in the trafficking and functional expression of the calcium channel complex.Upregulation of the α2δ-1 subunit in rat dorsal root ganglion (DRG) neurons occurs in several animal models of neuropathic pain, and results in an increase in trafficking of α2δ-1 to the presynaptic terminals of DRG neurons. This is inhibited by the α2δ-1 ligand pregabalin (Bauer et al., 2009).Co-cultures of embryonic rat spinal cord neurons and dorsal root ganglion neurons were used to examine synaptic transmission between the neurons, and the impact of pregabalin on this process. We have examined synaptic transmission by using both Fura-2 calcium imaging and in vitro electrophysiology.The F340/380 ratio was increased in DRGs upon exposure to capsaicin because of Ca2+ entry, and (with a delay) there was also an elevation in dorsal horn neurons. In a parallel experiment, the corresponding increase in observed EPSCs frequency in dorsal horn neurons was 3.0 ± 0.5-fold (n=14). The non-NMDA receptor antagonist CNQX (10 μM) caused a complete and reversible inhibition of the observed EPSCs.In dorsal horn monocultures there was no significant increase in EPSC frequency in response to capsaicin application. In addition, no increase in the F340/380 ratio was observed in dorsal horn neuron monocultures in response to capsaicin.Co-cultures were also incubated with pregabalin. The observed increase in EPSC frequency in control cells was 3.2 ± 1.5-fold (n=9), compared to a 1.5 ± 0.3-fold (n=6) increase cells treated with pregabalin (100 μM) for 48 hours. These data suggest that chronic pregabalin treatment reduced synaptic transmission between DRGs and dorsal horn neurons.Bauer et al. (2009). J Neurosci. Apr 1;29(13):4076-88.