Influence of nerve growth factor on chick trigeminal motor nucleus explants.

Explants of the metencephalic basal plate from stage 11 (40-hour) chick embryos containing the trigeminal (V) motor nucleus were cultured in standard control medium, in medium supplemented with nerve growth factor (NGF), in medium supplemented with NGF and specific antibodies to NGF (anti-NGF), and in medium supplemented with anti-NGF alone. The explants grown in the presence of NGF displayed an enhanced density and complexity of neuritic outgrowth, with this growth significantly surpassing that seen in the control group (p less than .001). The explants grown in NGF plus anti-NGF and those grown in anti-NGF alone did not differ from controls. The results indicate that this early cholinergic population is specifically responsive to NGF. This finding is consistent with recent studies in which NGF receptor binding has been found in this and other early brainstem and spinal cord motor neuron populations. The possible relevance of these observations to the normal sequence involved in the development of the V motor nucleus is discussed, particularly as they may relate to the relationship between the V ganglion and the developing V motor population.