Local GABAergic signaling within sensory ganglia controls peripheral nociceptive transmission

Abstract

Figure 1. Stimulus-induced release of GABA from DRG neurons. (A-E) "Sniffing patch" experiments. (A) Coculture of DRG neurons with HEK293 cells transiently cotransfected with 1 , 2 , and 2 GABA A subunits and GFP (HEK GABAA cells). (B) An example of recording from the GFP-positive HEK GABAA cell juxtaposed to a small-diameter rat DRG neuron (as shown in A). Timing of GABA (200 M) and capsaicin (CAP, 1 M) applications is indicated by the arrows. (C) A similar experiment but with HEK GABAA monoculture (no DRG neurons present). (D) A recording from a nontransfected HEK293 (HEK control ) cell in close apposition to a small DRG neuron. (E) Mechanical stimulation of DRG neuron in HEK GABAA -DRG coculture did not activate inward current in HEK GABAA cell. (F) Summary of the experiments shown in B-E; number of responsive cells from the total number of recordings is indicated within/above each bar. (G) Summary of experiments shown in E; "Mechano" indicates mechanical stimulation of DRG neuron adjacent to the "sniffing" HEK GABAA cell. *Significant difference from baseline at P < 0.05 (1-way ANOVA with Bonferroni correction). (H-L) HPLC analyses. (H) Release of GABA from the dissociated DRG cultures in response to various stimuli (as indicated). (I) Similar to H but acutely extracted, non-dissociated DRGs were used. Asterisks indicate significant difference from basal release: *P < 0.05, **P < 0.01, ***P < 0.001 (1-way ANOVA with Bonferroni correction). Number of experiments is indicated within each bar. (J-L) Effects of the synaptic transmission inhibitors concanamycin A (0.5 M; J) and tetanus toxin (10 g/ml; K), as well as the GAT1 blocker NO711 (200 M; L), on the basal and high-extracellular-K + -induced GABA release from acutely extracted whole DRGs. Asterisks indicate significant difference from basal release: *P < 0.05, **P < 0.01, ***P < 0.001; number symbols indicate significant difference from high-K + -induced release: # P < 0.05, ## P < 0.01, ### P < 0.001 (1-way ANOVA with Bonferroni correction). Number of experiments is indicated within each bar.