Molecular characterization of NOS in a mollusc: expression in a giant modulatory neuron.

Here we report on the molecular characterization of the first molluscan NOS in the CNS of the pond snail Lymnaea stagnalis. This Lymnaea NOS (Lym-nNOS) which is expressed preferentially in the CNS is most similar to mammalian neuronal NOS but contains tandem repeats of a seven amino acid motif not found in any other known NOS. We have localized Lym-nNOS to the serotonergic cerebral giant cells (CGCs) which modulate synaptic transmission within a neural network that generates feeding behavior. Our results suggest that the CGCs employ both NO and serotonin in the modulation of the central neural network underlying feeding.