Electrical properties of ‘dark green’ and ‘yellow’ neurosecretory cells in the snail Lymnaea stagnalis L.

Abstract

A NUMBER of electrophysiological investigations of neurosecretory neurones have been carried out in gastropod molluscs^1–6 but in every case except one⁵ the neurosecretory status and function of the cells was uncertain. In the pulmonate snail Lymnaea stagnalis L., substantial morphological and histochemical evidence obtained by light and electron microscopy exists for regarding the ‘dark green’ (DGCs) and ‘yellow’ (YCs) neurones as neurosecretory^6–8. The distinction between DGCs and YCs was based on their colour reaction to a combined Alcian blue–Alcian yellow staining technique used on sections of fixed brain material viewed under the light microscope⁷, but differences in elementary neurosecretory granule diameter and axon terminal location have also been found^7,8. Good evidence also exists for a function of DGCs and YCs in ionic or osmotic regulation in Lymnaea; the rate of release of both DGC and YC neuroendocrine material increased when snails were kept in deionised water and decreased in hypertonic saline^8–10. We show here that it is possible to identify DGCs and YCs in electrophysiological experiments and characterise them on the basis of their location, appearance and electrical properties in the live brain.