Development of Galanin- and Enkephalin-Like Immunoreactivities in the Sympathoadrenal Lineage of the Avian Embryo

Abstract

The neurochemical differentiation of the sympathoadrenal nervous system has been analyzed by focusing on the developmental expression of two neuropeptides, galanin and enkephalin. Both peptides are expressed early in the formation of the sympathetic ganglia and adrenal gland. Expression in the adrenal persists during embryogenesis to hatching while expression in the sympathetic is lost as sympathoblasts differentiate into neurons. Galanin expression and its modulation by nerve growth factor (NGF) and dexamethasone (Dex) was also studied in vitro. Differential effects of these factors were found on adrenal versus sympathetic cultures. However, the results coincided with proposed role of the factors in inducing either neuronal properties (NGF) or chromaffin characteristics (Dex).