Amine modulation of electrical coupling in the pyloric network of the lobster stomatogastric ganglion

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Abstract
The neurons of the pyloric network of the lobster (Panulirus interruptus) stomatogastric ganglion organize their rhythmic motor output using both chemical and electrical synapses. The 6 electrical synapses within this network help set the firing phases of the pyloric neurons during each rhythmic cycle. We examined the modulatory effects of the amines dopamine (DA), serotonin (5HT) and octopamine (Oct) on coupling at all the electrical synapses of the pyloric network. Electrical coupling within the pacemaker group [anterior burster (AB) to pyloric dilator (PD), and PD- Dopamine decreased or increased the coupling strength of all the pyloric electrical synapses: the sign of the effect depended upon which neuron was the target of current injection. For example, DA decreased AB→ PD coupling (i.e., when current was injected into the AB) but increased coupling in the other direction, PD→ AB. Dopamine decreased AB to VD coupling when current was injected into either neuron. Serotonin also had mixed effects; it enhanced PD→AB coupling but decreased AB to VD and PD to VD coupling in both directions. Octopamine's only effect was to reduce PD→ VD coupling. li]4. The characteristic modulation of electrical coupling by each amine may contribute to the unique motor pattern that DA, 5HT and Oct each elicit from the pyloric motor network.