The axon reaction of the goldfish mauthner cell and factors that influence its morphological variability

The axon reaction of the goldfish Mauthner cell, elicited by spinal cord transection, included somatic swelling, nuclear eccentricity, chromatolysis, nuclear infolding, and a perinuclear buildup of basophilic material. The latter three changes were found most consistently and showed gradations which were ranked quantitatively. The time of onset of chromatolysis and nucleus‐associated changes depended upon the distance of the wound from the Mauthner cell soma. Specifically, for Mauthner axons cut at 5, 10.5, and 20 mm distal to their somata, the approximate postoperative times of onset were 10, 20, and 40 days, respectively. Mauthner cells axotomized 42 mm distally did not display a consistent axon reaction. Cell atrophy and death were not found in cells axotomized 10.5, 20, or 42 mm from their somata up to 285 postoperative days, but were observed at the longer postoperative intervals (421 days) in neurons cut 5 mm distally and were consistently found in neurons axotomized less than 1.6 mm from their somata. The axon reactions of Mauthner cells within a pair were frequently different. This variability cannot be explained by the influence of cut site or postoperative interval and is hypothesized to result from different metabolic conditions of the individual cells.