GABA_A receptors mediate responses to GABA in human C-fibres.

<p>Increases in the electrical excitability index of unmyelinated axons in human sural nerve fascicles following bath application of GABA (10–30 µM) are blocked by prior application of the GABA_A receptor antagonists bicuculline (20 µM, grey bar A), picrotoxin (10 µM, grey bar B) and gabazine (10 µM, grey bar C). In contrast to both bicuculline and gabazine, the blocking effect of picrotoxin is not reversed upon wash-out (B). The pooled effect of each compound on the change in excitability index following bath application of GABA (10 µM) is shown in panel D. A significant reduction in the response to GABA (10 µM) was observed in the presence of gabazine (p<0.05, Student's paired t-test) and bicuculline (p<0.05, Student's paired t-test). Owing to the limited availability of human nerve fascicles a statistical comparison was not made for three fascicles exposed to picrotoxin.