TABLE 3.

Counts of the L4 DRG Neurons and Myelinated Nerve Fibers in the L4 DRs and Medial Gastrocnemius Muscle Nerve in WT and Mutant Mice at P21^a

Genotype	L4 DRG neurons	L4 DR nerve fibers	Muscle nerve fibers
WT	9,255 ± 192 (8)	2,495 ± 74; (7)	138 ± 2 (11)
myoNT3	10,050 ± 325 (8)*	2,914 ± 156 (7)*	210 ± 6 (8)**
Er81−/−	7,585 ± 189 (7)**	1,776 ± 39 (7)**	121 ± 3 (15)*
myoNT3;Er81−/−	8,871 ± 197 (13)*,b,c	2,451 ± 60 (16)*,b,c	178 ± 2 (8)*,b,c

^aNote the deficits in numbers of sensory neurons and nerve fibers in Er81^−/− mutants and excess neurons and nerve fibers in myoNT3 mutants relative to wild-type mice. Overexpression of NT3 in muscle augmented the number of neurons and nerve fibers in myoNT3;Er81^−/− double relative to Er81^−/− single mutants. Means ± SEM (N) of counts are shown. Values denoted by an a single or double asterisk are significantly different from wild-type values at P < 0.05 or P < 0.001, respectively.

^bA significant difference from myoNT3 at P < 0.05.

^cA significant difference from Er81^−/− at P < 0.05.

L4, lumbar 4; DRG, dorsal root ganglia; DR, dorsal spinal root; WT, wild-type; P21, postnatal day 21; NT3, neurotrophin-3.