Percentage of PPN cells manifesting both N+P/Q-type calcium channels (outer ring), PPN cells manifesting only N-type channels (middle ring), and those manifesting only p/Q-type channels (inner ring). The proportion of type I cells is in brown (13–16%), of type II cells is in purple (66–68%), and of type III cells (13–16%). These results suggest that all three electrophysiological types, and probably all three transmitter types (type I cells are non-cholinergic, type II cells are 2/3 cholinergic, and type III cells are 1/3 cholinergic) bear all three calcium channels types (N only, P/Q only, both N+P/Q) (Kezunovic, et al., 2011; D’Onofrio, et al., 2015; Luster, et al., 2015).