Figure 7. α₂-NA receptor stimulation inhibits HCN currents via a PLC–PKC signalling pathway.

A, dialysis with the adenylate cyclase inhibitors SQ22536 (1 mm, n= 5), 2′,5′-dideoxyadenosine (0.1 mm, n= 5), or MDL 12 330 (0.5 mm, n= 5) did not prevent the increase in evoked spikes per pulse produced by clonidine (10 μm) in current clamp. B, summary of the current–voltage relationship of the clonidine-sensitive current under control conditions (^, n= 6, data from Fig. 3E) or from cells dialysed with SQ22536 (1 mm, •, n= 6). Points are means ±s.e.m.C, the effects of clonidine on evoked firing were blocked by the PLC inhibitor U73122 (10 μm in pipette, n= 5). The PKC antagonists calphostin C (1 μm in pipette, n= 6) and chelerythrine (1 μm in bath, n= 7) also prevented the increase in evoked spikes per pulse produced by clonidine in current clamp. D, summary of the current–voltage relationship of the clonidine-sensitive current under control conditions (^, n= 6, data from Fig. 3E) or in the presence of chelerythrine (•, n= 6). *P-value < 0.05.