Homeostatic compensation and neuromodulation maintain synchronized motor neuron activity in the crustacean cardiac ganglion

Motor neurons of the crustacean cardiac ganglion have variable intrinsic conductance magnitudes, yet produce virtually identical synchronized voltage activity. However, it is not known whether this variability makes cells vulnerable to desynchronization during neuromodulation. Previous work has investigated whether neuromodulation of variable networks can produce reliable responses in particular features of network output, but these studies have not examined this question as it relates to synchrony. To investigate this, we exposed the cardiac ganglion to the amine modulators serotonin and dopamine while recording from multiple motor neurons. Each amine had distinct excitatory effects, and serotonin caused desynchronized activity whereas dopamine did not. Dopamine was found to directly modify gap junctional conductance, and co-application of both modulators induced a serotonin-like response in network activity, but burst waveforms remained synchronized. Dopamine was also able to prevent desynchronization induced by the K channel blocker tetraethylammonium (TEA), suggesting that dopaminergic modulation of electrical coupling potentially plays