Figure 6. In combination, P2 receptor antagonist and gap junction blockers decrease CO₂/H⁺ sensitivity by an amount similar to each blocker alone.

A, trace of firing rate shows that under control conditions exposure to 15% CO₂ increased neuronal activity ∼2 Hz. A second exposure to 15% CO₂, this time in the presence of suramin to block P2 receptors and cobalt to block gap junction hemichannels, increased firing rate only ∼1 Hz or 72% of control. The asterisk indicates an 8 min time break. CO₂ sensitivity fully recovered after washing out suramin and cobalt. B, summary data (n = 3) show that in combination suramin and cobalt decreased CO₂/H⁺ sensitivity of RTN neurons by 28 ± 3.0%. C, the per cent inhibition by suramin and cobalt acting together is not different from that of either blocker alone.