Identification of Neurons Containing Vertebrate-Type Brain-Gut Peptides by Antibody and Cobalt Labelling

Abstract

Different chemical compounds such as cobalt chloride, heme proteins and fluorescent dyes (e.g. Procion yellow and Lucifer yellow) have proved invaluable for tracing neurons. They do not, however, reveal the identity of the chemical contents, whereas immunocytochemistry does. Immunocytochemical methods are inferior, however, for revealing the complete dendritic domain and axonal pathway of a particular cell due to a variety of reasons. First, with the thin sections (5–10 µm) obligatory for this technique, a curved and branched axonal pathway cannot be followed very far since the plane of section does not usually coincide with the axonal trajectory. Second, there are considerable variations in the metabolic activities of peptidergic neurons that are reflected in a changing distribution of material in both the perikarya and the axons. Factors such as age, diet, sex and, possibly, behavioural history are very important in determining how much of a particular pathway is stainable at any particular time (see also Chap. 13).