EFFECTS OF NERVE GROWTH FACTOR ON CYCLIC AMP LEVELS IN EMBRYONIC CHICK DORSAL ROOT GANGLIA FOLLOWING FACTOR DEPRIVATION

Abstract

AbstractNerve growth factor (NGF) at 10 B.U./ml produced a 5‐fold increase in the concentration of cyclic AMP 10min after addition to freshly excised embryonic chick dorsal root ganglia (DRG). The presence of NGF at 10 B.U./ml, but not 1 B.U./ml, over a 6 h incubation in nutrient‐free medium prevented this cyclic AMP increase when the DRG were again challenged with NGF (10 B.U./ml) after the 6 h. Incubation of DRG for 6 h at 37°C without NGF did not prevent the cyclic AMP response from occurring when NGF was presented at this time. The basal cyclic AMP concentration, however, decreased by 65–75% during the course of the 6 h incubation, and the continuous presence of NGF (10 B.U./ml) was unable to prevent this. When NGF was added to 6‐h NGF‐deprived DRG, the time for maximum cyclic AMP increase decreased from 15min to 6min with increasing NGF concentrations from 1 to 50 B.U./ml, although the relative magnitude of the cyclic AMP increase was essentially the same (approx 3‐fold) at these NGF concentrations.Attempts were made to correlate the cyclic AMP response in NGF‐deprived DRG with another rapid response resulting from administration of NGF to NGF‐deprived DRG, namely, the reactivation of hexose uptake. The cyclic AMP and permeation responses both occurred on the same time scale (5‐15 min), and both responded to increasing concentrations of NGF with a decreasing time to achieve maximal effect. A temporal relationship between cyclic AMP and membrane permeability was noted, but it could not be ruled out that it might reflect difficulties in methodology and/or inadequacy in current knowledge of the underlying mechanisms.