Figure 7

Activation and subsequent desensitisation of GABA receptors fails to prevent the modulation of voltage-activated Ca²⁺ channels in cultured DRG neurones by pregabalin. A) Bar chart showing data obtained from neurones that responded to GABA (100 μM). All data are normalised with respect to the first Ca²⁺ transient evoked by 30 mM KCl. Open bars show the relative responses to 100 μM GABA in cells (n = 3) where 25 μM pregabalin enhanced the Ca²⁺ flux. Filled bars show responses in cells (n = 15) where 25 μM pregabalin inhibited the Ca²⁺ flux. Data are shown for GABA responses (GABA), K⁺-evoked Ca²⁺ transients under control conditions with GABA present (Ctrl), K⁺ evoked Ca²⁺ transients in the presence of GABA and 25 μM pregabalin (PGB) and on recovery in the continued presence of GABA (Rec). B) An example trace, showing a response to 100 μM GABA and Ca²⁺ transients evoked by K⁺ in the presence and absence 25 μM pregabalin. The long open bar shows the period of GABA application, the short open bars show K⁺ stimulation and the filled bar the period of pregabalin application. C) Bar chart showing data obtained from neurones that did not responded to GABA (100 μM) but were continually bathed with GABA for the duration of the experiment. All data are normalised with respect to the first Ca²⁺ transient evoked by 30 mM KCl. Data are shown for K⁺-evoked Ca²⁺ transients under control conditions with GABA present (Ctrl), increased (n = 10; open bars) and decreased (n = 13; filled bars) K⁺-evoked Ca²⁺ transients in the presence of GABA and 25 μM pregabalin (PGB) and on recovery (Rec). D) An example trace, showing no response to 100 μM GABA but responses to K⁺ in the presence and absence of 25 μM pregabalin. The long open bar shows the period of GABA application, the short open bars show K⁺ stimulation and the filled bar the period of pregabalin application.