Tunicamycin-Induced Cell Death in the Trigeminal Ganglion is Suppressed by Nerve Growth Factor in the Mouse Embryo

The effect of nerve growth factor (NGF) on tunicamycin (Tm)-treated neurons in the trigeminal ganglion was investigated by use of caspase-3 immunohistochemistry. In intact embryos at embryonic day 16.5, only a few caspase-3-immunoreactivity were detected in the ganglion neurons. Mean ± SE of the density of the immunoreactivity was 0.22 ± 0.03%. In contrast, the number of the immunoreactive neurons was increased at 24 h after injection of 0.5 μg Tm in 1 μl of 0.05 N NaOH solution into mouse embryos at embryonic day 15.5. The density of immunoreactivity was also increased (mean ± SE = 1.44 ± 0.11%) compared to intact and 0.05 N NaOH-treated embryos (mean ± SE = 0.35 ± 0.03%). The Tm treatment caused increase of the number of trigeminal neurons representing apoptotic profiles (intact, mean ± SE = 79.3 ± 8.5; 0.05 N NaOH, mean ± SE = 132 ± 11.5; 0.5 μg Tm, mean ± SE = 370.2 ± 64.8). In addition, NGF significantly prevented the increase of density of the immunoreactivity (mean ± SE = 0.54 ± 0.16%) and the number of apoptotic cells (mean ± SE = 146.2 ± 11.3). Saline application (without NGF) had no effect on Tm-induced increase of the immunoreactivity (mean ± SE = 1.78 ± 0.23%) or the apoptotic profiles (mean ± SE = 431.9 ± 80.5). These results indicate that Tm-induced cell death in the trigeminal ganglion is suppressed by NGF in the mouse embryo.