Morphological and electrophysiological features of F76 and D1 neurones of the sub-oesophageal ganglia of Helix aspersa in vitro and in culture.

Identified neurones F76 and D1 of the suboesophageal ganglia of Helix aspersa were studied in the isolated ganglia in vitro and in culture. The neurones were examined electrophysiologically with current clamp and morphologically either with intracellular injections of Lucifer Yellow or biocytin. These nerve cells had very similar resting membrane potentials and responses to injected current. The projections of D1 and F76 have been characterised, with both neurones having two main axons. The F76 neurones project to the left pallial, right pallial, anal, and visceral nerves as well as to the left and right pleural ganglia. The D1 neurones have similar projections except that they do not project to the anal and visceral nerves. The bilateral symmetry to the pallial nerves and pleural ganglia is discussed. These cells were also studied electrophysiologically after mechanical isolation and culture. F76 and D1 neurones were separated by dissection (no enzymes) and cultured in three ways. In normal snail Ringer they remained viable for up to two weeks with no development. In Ringer preincubated with a ganglia or containing endothelial growth factor, neurite outgrowths were seen. Membrane potentials were significantly lower in cultured neurones than in vitro and the after hyperpolarization never went below resting in cultured cells but it did in vitro.