Table 1.

Probability of axonal regeneration for spinal-projecting neurons

	Group 1	2A	2B	3	4	5	6A	6P	7	8	9	10
CTRLS ± SE (n = 8)	13.3  ± 1.2	17.5  ± 1.3	7.3  ± 0.7	20.6  ± 2.0	28.6  ± 2.4	37.5  ± 2.7	14.0  ± 2.5	28.3  ± 2.1	399.5  ± 24.3	17.0  ± 1.4	25.1  ± 2.9	87.7  ± 7.6
TRANS ± SE (n = 27)	1.8  ± 0.3	5.3  ± 0.6	3.7  ± 0.3	11.9  ± 0.9	15.2  ± 1.1	11.7  ± 1.2	7.5  ± 0.6	20.7  ± 1.3	123.8  ± 7.9	4.1  ± 0.4	4.3  ± 0.8	32.9  ± 3.1
% REG ± SE	13.8  ± 2.1	30.3  ± 3.6	51.0  ± 4.7	57.4  ± 4.1	53.1  ± 3.7	31.3  ± 3.2	53.4  ± 4.4	73.3  ± 4.5	31.0  ± 2.0	24.2  ± 2.4	17.0  ± 3.0	37.5  ± 3.5

For each of 12 previously described cytoarchitectonic groups (Swain et al., 1993), the number of neurons per side projecting beyond the level of the fifth gill was determined by retrograde transport of HRP in eight control (CTRLS) large larvae (see Materials and Methods). The probability of regeneration for each of these neuronal groups was determined in 27 animals that had received a spinal transection (TRANS) at the level of the fifth gill and were allowed to recover for 65–95 d. After recovery, HRP was injected 5 mm caudal to the lesion, and the number of retrogradely labeled neurons was counted. In each animal, the percentage regeneration (% REG) was calculated for each neuron group by comparing the number of labeled neurons with the mean neuron count for that group in control animals. The names of the 12 neuron groups are indicated in Figure 1.