Si1 is a Neuron in Melibe.
- Names and Aliases - Swim Interneuron 1, Si1.
- Species: Melibe leonina
- Neurotransmitter: Unknown
There is one Si1 in each hemisphere of the cerebropleural ganglion. The axon projects ipsilaterally to the pedal ganglion. Si1 is an integral component of the central pattern generator that produces lateral-flexion swimming. Si1 fires rhythmic bursts during a swim motor pattern that are in phase with ipsilateral swim neurons and antiphase with contralateral swim neurons.
- Non-serotonergic neuron that is surrounded by CeSP neurons and projects to ipsilateral pedal ganglion.
- Soma located just posterior and lateral to the tentacular lobe, and just medial to the three serotonergic CeSP-A neurons.
- Soma has larger diameter than other neurons in its vicinity.
- The axon projects ipsilaterally to the pedal ganglion, with fine branches projecting anteriorally in both the cerebral and pedal ganglia. The axon continues out the larger of the two pedal-pedal connectives (PP2 according to nomenclature in Newcomb et al, 2006) to the contralateral pedal ganglion.