STIMULATORY EFFECTS OF SUBSTANCE P ON NEURITE EXTENSION AND CYCLIC AMP LEVELS IN CULTURED NEUROBLASTOMA CELLS

Abstract— Synthetic substance P initially increased cyclic AMP levels and subsequently induced neurite extension in cultured neuroblastoma N 18 cells. The magnitude of these effects depended on the concentration of fetal calf serum (FCS) in the culture medium, being more evident in the presence of a lower (0.1%) concentration of FCS.
In Eagle's medium containing 0.1% FCS, low concentrations of substance P (10^?7-10^?5 M) increased cyclic AMP levels and stimulated neurite extension.
In Eagle's medium containing 5%FCS, both substance P at concentrations of 10^?5-10^?3M and dibutyryl cyclic AMP at concentrations of 10^?4-10^?2M increased cyclic AMP levels and stimulated neurite extension. The activities of acetylcholinesterase, (Na⁺+ K⁺)-, HCO₃^? and Mg²⁺ -stimulated-ATPase were also increased. Cell growth was inhibited.
Substance P at concentrations of 10-⁷-10^?5M also stimulated the adenylate cyclase activity of a particulate fraction of N 18 in a concentration-dependent manner.