Fig. 8.

Input to CBIs during the CMP in the isolated cerebral ganglion. A, CBI-1 was weakly, slowly inhibited during the CMP, in phase with the fast IPSPs in C12. B, CBI-2 and CBI-4 received slow excitation during the CMP, which depolarized them above spiking threshold. C, CBI-3 was excited and spiked during the CMP, in phase with the IPSPs in C12 (not shown) and the EPSPs in C4. D, CBI-3 andC4 were electrically coupled, because hyperpolarizing or depolarizing current pulses in either neuron (solid bars) led to a smaller membrane potential change of the same polarity in the other. Action potentials in one neuron gave rise to brief depolarizing potentials in the other without a measurable delay. E, The excitation seen in CBI-3 during a cycle of the CMP induced by firing ofC15 (E1) was effectively mimicked by a depolarizing current pulse into C4 (E2), showing that electrotonic transmission of the chemically mediated excitation and spiking in C4 is sufficient to explain the excitation recorded in CBI-3.