Morphology of two electrotonically-coupled giant neurosecretory neurons in the snail, Lymnaea stagnalis

Abstract

1. 1. Giant neurosecretory neurons, VD1 and RPD2, stain yellow with the Alcian Blue-Alcian Yellow staining technique for neurosecretion. VD1 stains more intensely than RPD2. 2. 2. VD1 has main anteriorly-directed axons to the left- and right-hand side of the c.n.s. with extensive but variable projections to the nerves of the visceral and parietal ganglia. 3. 3. RPD2 has its main axonal projection to the intestinal nerve but other constantly occurring projections to three nerves of the visceral and right parietal ganglia. Anteriorly-directed axons project through the left- and right-hand sides of the (central nervous system) c.n.s. but are finer than those in VD1. 4. 4. The site of the electrotonic junction between VD1 and RPD2 is located in the viscero-right parietal connective or visceral ganglion neuropile. 5. 5. Release of neurosecretory material in both cells can take place from extraganglionically projecting axons in the connective tissue surrounding the central ganglia and probably from the surface of central connectives and peripheral nerves close to the c.n.s.