Developmental changes in axon terminals visualized by immunofluorescence for the growth-associated protein, GAP-43, in the robust nucleus of the archistriatum of the zebra finch

Abstract Two afferents to the robust nucleus of the archistriatum (RA) are important for song learning by the zebra finch. The growth-associated protein-43 (GAP-43) has been used as a molecular marker for axonal growth. In these experiments, the axon terminals were visualized by immunofluorescence with antibodies against GAP-43 and we studied the developmental processes in the zebra finch after the invasion of the RA by afferent fibers. After waiting at the dorsal border of the RA before invading the RA, the axon terminals from the higher vocal center (HVc) first contacted the soma, and then redistributed and established synapses on the dendrites. The initial contact with the soma may be closely related to the neurotrophic properties of the axon terminals from the HVc neurons.