THE EXPRESSION OF B-50 GAP-43 DURING DEVELOPMENT OF RAT SPINAL NEURONS IN CULTURE IS REGULATED BY INTERNEURONAL CONTACT

The neuron-specific phosphoprotein B-50 (GAP-43) is associated with neuritogenesis during development and regeneration. We monitored B-50 in cultured spinal neurons (fetal rat) with an enzyme-linked immunoadsorbent assay. B-50 levels increased from 24 to 72 h, then decreased. Other cultures, fixed at 24 h intervals and incubated with anti-B-50 immunoglobulins and fluorescent conjugates, showed that B-50 was present in somata after 24 h, but mainly in neurites after 48 h; after 72-96 h neurons migrated into clusters and B-50 was detected only in free neurites at the perimeter of the culture. We conclude that B-50 expression is down-regulated by neurite-cell or cell-cell contact. © 1990.