Synthesis of Nerve Growth Factor mRNA in Cultures of Developing Mouse Whisker Pad, a Peripheral Target Tissue of Sensory Trigeminal Neurons

The study investigated the synthesis of nerve growth factor (NGF) mRNA in developing mouse whisker pads, a peripheral target tissue of sensory trigeminal neurons. It was found that the increase in NGF mRNA levels in the mouse maxillary process/whisker pad was not directly linked to epidermal differentiation, as evidenced by the fact that retinoic acid, which prevents epithelial differentiation, did not affect NGF mRNA levels. In cultures, the timing of NGF mRNA production varied with the age of the explanted tissue, with E11.5 explants showing a pattern similar to in vivo conditions. Earlier stage explants (E10/10.5) showed a slow increase in NGF mRNA, which was significantly enhanced by a soluble factor produced by E11.5 explants, but not by IL-1 beta and TGF-beta 1. This suggested that a specific soluble factor within the tissue strongly stimulated NGF mRNA production.