Exogenous NGF Research Articles

Different effects of nerve growth factor on cultured sympathetic and sensory neurons

Long-term cultures of dissociated nodose ganglion (NG) and superior cervical ganglion (SCG) neurons from newborn rabbits were used to compare their response to nerve growth factor (7S NGF). SCG neurons required added NGF for their survival and a concentration of 1 μg/ml was found to be optimal. NG neurons, on the other hand, survived well for a long term without addition of NGF, but its application (1 μg/ml) was found to be effective in accelerating the growth of fibers (neurites) and neuronal somata. It is concluded that unlike SCG, NG neurons do not depend on exogenous NGF but may require an intrinsic trophic-like factor which may be contained in the serum of the medium, emanating from glial cells or by metabolic cooperation between neurons.

Ionic behaviors and nerve growth factor dependence in developing chick ganglia: II. Studies with neurons of dorsal root ganglia

Using intact dorsal root ganglia (DRG) from embryonic (E) chick and measuring 22Na + accumulation, the authors have recently shown that (i) ionic control by the ganglia has a complete requirement for exogenous NGF between E6 and E10, and (ii) control of ion pump mechanisms independent of exogenous NGF is progressively acquired by these ganglia from E10 to E16. Similar experiments have now been carried out using enriched suspensions of ganglionic neurons to test whether the acquisition of endogenous control by older ganglia was (1) due to the close association between neurons and nonneurons, and (2) correlated with a decreasing need by these neurons for exogenous NGF for survival in culture. In this enriched neuronal population, Na + accumulation in the absence of NGF increases from E7 to E10, paralleling the increase in Na + accessible space under ouabain, but then decreases conspicuously between E10 and E16, despite little change in the ouabain-sensitive Na + space. NGF prevents Na + accumulation during the early period, and becomes increasingly irrelevant for this behavior in later (after E10) development. K + movements (traced with 86Rb +) behaved similarly. Active K + influx (Na +, K +-pump mediated) also increases severalfold between E7 and E10. This K + influx is sensitive to NGF at E7 and E10 but not at E14, paralleling the observed Na + and K + behaviors. These data suggest that the control of Na +,K +-pump performances acquired by these neurons between E10 and E16 represents the development of a neuronal self-sufficiency. This increase in ionic control is not due to an increase in pump molecules or pumping efficiency. No increases in the binding of [ 3H]ouabain or active K + influx occur between E10 and E16, when ionic control is developing. The ionic dependence on NGF by the DRG neurons changes with their developmental age along the same temporal pattern displayed by their survival response to NGF in culture.

Short-latency ionic effects of nerve growth factor deprivation and readministration on ganglionic cells.

AbstractNerve growth factor (NGF) is likely to exert its trophic action on dorsal root ganglion (DRG) and on sympathetic ganglion neurons by controlling a crucial function of these cells. This function would in turn regulate other cellular machineries and, ultimately, lead to the traditional NGF consequences, such as survival and neuritic growth. A corollary of this view is that the key to NGF action must lie in short‐latency events, occurring within minutes of NGF administration. Chick embryo DRG dissociates have proved to be an effective experimental system to investigate short‐latency responses to NGF, in that (1) measurable functional deficits develop over 6 h of NGF deprivation in vitro and (2) delayed presentation of NGF promptly and fully restores the defective function. The first deficit observed in this experimental system, a decline in RNA‐labeling capability, led to the recognition that NGF controls the transport of selected exogenous substrates, all of which are Na+‐coupled and depend on an Na+ gradient across the neuronal membrane. Subsequent work showed that NGF controlled such transport systems by actually regulating the neuronal ability to control intracellular Na+. Under NGF deprivation, the DRG cells accumulate Na+ to levels that reflect, and presumably equate, the extracellular Na+ concentrations. Conversely, on delayed NGF administration, the accumulated Na+ is actively extruded to an extent and at a speed that depends on the NGF concentration. The Na+ response is elicited by both Beta and 7S NGF, but not by other proteins tested. All ganglionic systems that display a requirement for exogenous NGF in culture have also displayed the Na+ response to NGF. The Na+ response is grossly paralleled by a K+ response. DRG dissociates, in which intracellular K+ has been pre‐equilibrated with extracellular 86Rb+, lose their 86Rb+ over 6 h of NGF deprivation and restore it on delayed NGF administration. The regulation by NGF of mechanisms controlling intracellular Na+ and K+ levels in their target neurons is likely to occupy an early and fundamentl place in the sequence of events underlying the mode of action of this factor.

The role of nerve growth factor in vitro in cell resistance to 6-hydroxydopamine toxicity

Abstract Cell resistance to the catecholaminergic neurotoxin 6-hydroxydopamine was studied in various cell lines: human neuroblastoma lines SK-N-MC. SK-N-SH, and SK-N-SH-SY5Y; and non-neuroblastoma lines CHO-K1, S-180, C-6, and L-M, the latter three of which synthesize nerve growth factor. Cells were treated one day after seeding for 1 h with 6OHDA. Cytotoxicity of the drug was quantified as the percent live cells, determined by the trypan blue exclusion test, 24 h after treatment. At 100 μg/ml, 6OHDA lethal toxicity was confined mainly to neuroblastoma cells. However, drug specificity was dependent not only on cell type, but also on cell density and presence of NGF. Thus, the non-neuroblastoma cell strain S-180-A, which produces less NGF than its parent line S-180, lost resistance to toxicity at low cell density, and even at high density was less resistant than SK-N-MC neuroblastoma cells. Moreover, when mouse β-NGF (500 BU/ml) was administered to human neuroblastoma clones SY5Y and IN one day after seeding for 24 h before drug treatment, the cell survival rate increased significantly, although only SY5Y cells were protected by a lower concentration (1 BU/ml) of exogenous NGF. Finally, cell line S-180 became susceptible to 6OHDA killing when incubated one hour with high titer anti-mouse β-NGF immediately prior to drug treatment, whereas cell line C-6 did not. NGF was therefore proposed to have an important, though not determinative, role in cell resistance to 6OHDA toxicity.