A light microscopical study of transganglionic degeneration in young rats of different ages.

Transganglionic degeneration (TGD) has been studied in the trigeminal nucleus caudalis of young rats of different ages with the aid of the Fink-Heimer technique at various intervals following peripheral nerve transection. In addition, the occurrence of TGD was examined in adult rats after retransection of a peripheral nerve originally transected at birth. The results showed no degeneration argyrophilia indicating TGD in the rats operated at birth regardless of the survival time. Small amounts of TGD appeared in rats operated at an age of about one week and surviving one to 4 weeks. Similar results were obtained in rats operated at 17-26 days of age and surviving for around one week, whereas longer survival times resulted in an increased amount of TGD. These findings suggest that nonargyrophilic forms of TGD predominate in the youngest rats, since other studies have demonstrated a substantial cell loss in the trigeminal ganglion of the neonatal rat following peripheral nerve injury. No degeneration argyrophilia was observed in the rats which were subjected to a retransection of the peripheral nerve when grown to adults. This might be a reflection of a severe cell loss after the initial transection and/or that regenerating neurons will react more like immature neurons.