COINDUCTION OF NEURONAL INTERFERON-GAMMA AND NITRIC-OXIDE SYNTHASE INRAT MOTOR-NEURONS AFTER AXOTOMY - A ROLE IN NERVE REPAIR OR DEATH

Induction of an interferon-gamma-like molecule, previously isolated fr om neurons (N-IFN-gamma), and of the neuronal isoform I of the synthet ic enzyme of the free radical nitric oxide, nitric oxide synthase I, a s well as of NADPH-diaphorase, were examined in axotomized dorsal moto r vagal and hypoglossal neurons. Unilateral transection of the vagal a nd hypoglossal nerves was performed in the same rat and an induction o f N-IFN-gamma and nitric oxide synthase I immunostaining as well as NA DPH-diaphorase histochemical positivity was observed in the ipsilatera l motoneurons after 2-4 days. The immuno and enzyme- histochemical pos itivities were much stronger in the dorsal motor vagal neurons than in hypoglossal neurons. Two and 4 weeks after axotomy N-IFN-gamma immuno reactivity and NADPH-diaphorase positivity persisted in the former, bu t started to decrease in the latter neurons. Previous data have shown that 23 weeks after nerve transection the majority of the dorsal motor vagal neurons are lost, while the majority of the hypoglossal neurons survive. The high and persistent expression of N-IFN-gamma and nitric oxide synthase I af ter axotomy in the dorsal motor vagal neurons, th at af e largely destined to die, indicates that the co-induction of th ese two molecules may be implicated in the pathogenesis of neuronal de generation.