Fig. 1.

Dorsal view of a Lymnaea stagnalis central nervous system preparation after retrograde filling of the penial nerve with the nickel-lysine, showing the neuronal network regulating male mating. The cerebral commissure was cut after backfilling, and the cerebral ganglia placed to the sides to expose the pedal, pleural, and parietal ganglia. Retrograde-stained neurons appear bluish black. The arrow indicates an example of one of the dispersed cells in the right parietal ganglion that was selected for MALDI-TOF-MS analysis. The arrowhead indicates the giant neuron, right parietal dorsal one (RPD1). Different CNS backfills showed a variability of 5–10 stained neurons. Abbreviations: AL anterior lobe, rPe right pedal ganglion, PeI cluster I of pedal ganglion, PN penial nerve, rPa right parietal ganglion, rPl right pleural ganglion, rCG right cerebral ganglion, V visceral ganglion, VL ventral lobe