Endogenous bursters in central pattern generators (CPGs) generate rhythmic firing patterns controlling regular movements in the organism. Based on a pacemaker kernel model of the stomatogastric ganglion (SGG) of crustaceans, we constructed three reduced models, (i) dendrite-reduced model (DRM), (ii) axon-reduced model (ARM), and (iii) primary neuritereduced model (PNRM). Similar firing patterns were observed in two models except the axonreduced one. Perturbing of various parameters in the models induced bifurcation phenomena in the occurrence of interspike intervals (ISIs), which depicted variation of the firing patterns. By comparing and analyzing two-dimensional parameter planes derived from the above different models, the effects of compartments on varying firing patterns were detected. In particular, a different kind of period-doubling transition mode of firing patterns, which varied via a ring-shape mode, was found.