Retrograde axon reaction in the lateral vestibular nucleus of neonatal and adult rats.

Upper cervical cord lesions were performed in neonatal and adult rats (neonates survived for 10-20 days, adults 7-30 days). Retrograde axonal reaction was examined in the lateral vestibular nucleus. Nuclear eccentricity, which is a normal feature in neonatal lateral vestibular neurons, is not peculiar to adult neurons. As early as 7 days after cordotomy, neonatal neurons reacted severely, to the extent of atrophy and cell loss. Seven days after cordotomy, adult neurons were swollen, with eccentrically placed nuclei and Nissl granules which had undergone dissolution. The latter feature is regarded as the diagnostic feature in identifying reacting chromatolytic cells.