Figure 3. Calcium channel subtypes affected by GABA_B receptor activation .

A, baclofen (10 μm) suppressed the ramp‐generated inward calcium current (red vs. black traces). A ‘cocktail’ of L‐type calcium channel blockers (20 μm nifedipine, 100 μm verapramil, 20 μm nimodipine and 20 μm SR33805) reduced the inward current (blue trace) and the addition of baclofen to this cocktail produced an additional reduction in the calcium current (green trace). Extracellular calcium instead of barium was used as the charge carrier in this experiment. B, using the same protocol as in A, 10 μm baclofen reduced the inward current (red trace), 3 μm omega conotoxin GVIA (N‐type calcium channel blocker) reduced the recovered inward current (blue trace) but baclofen in the presence of omega conotoxin (green trace) had no additional effect.