Recovery of sympathetic nerve function after lumbar sympathectomy is slower in the hind limbs than in the torso

Abstract

Local sympathetic denervation by surgical sympathectomy is used in the treatment of lower limb ulcers and ischemia, but the restoration of cutaneous sympathetic nerve functions is less clear. This study aims to explore the recovery of cutaneous sympathetic functions after bilateral L_2-4 sympathectomy. The skin temperature of the left feet, using a point monitoring thermometer, increased intraoperatively after sympathectomy. The cytoplasm of sympathetic neurons contained tyrosine hydroxylase and dopamine β-hydroxylase, visualized by immunofluorescence, indicated the accuracy of sympathectomy. Iodine starch test results suggested that the sweating function of the hind feet plantar skin decreased 2 and 7 weeks after lumbar sympathectomy but had recovered by 3 months. Immunofluorescence and western blot assay results revealed that norepinephrine and dopamine β-hydroxylase expression in the skin from the sacrococcygeal region and hind feet decreased in the sympathectomized group at 2 weeks. Transmission electron microscopy results showed that perinuclear space and axon demyelination in sympathetic cells in the L₅ sympathetic trunks were found in the sympathectomized group 3 months after sympathectomy. Although sympathetic denervation occurred in the sacrococcygeal region and hind feet skin 2 weeks after lumbar sympathectomy, the skin functions recovered gradually over 7 weeks to 3 months. In conclusion, sympathetic functional recovery may account for the recurrence of hyperhidrosis after sympathectomy and the normalization of sympathetic nerve trunks after incomplete injury. The recovery of sympathetic nerve function was slower in the limbs than in the torso after bilateral L_2-4 sympathectomy.

Keywords: lumbar sympathectomy; nerve regeneration; neural regeneration; recovery of function; skin; sympathetic nerve.

Figure 1

Anatomy of the bilateral lumbar sympathetic trunk (indicated by arrows) in a rat.

Figure 2

Immunofluorescence staining results in the lumbar sympathetic trunk in rats under fluorescence microscope (× 200). (A, B) Immunofluorescence staining showed positive expression of tyrosine hydroxylase (green, A) and dopamine β-hydroxylase (red, B) in the cytoplasm of sympathetic neurons in excised sympathetic trunks. Scale bars: 100 μm.

Figure 3

Skin temperature of the left feet. (A) Intraoperative temperatures of the left feet skin during lumbar sympathectomy in rats. The abscissa represents time (seconds), and the ordinate represents temperature (°C). (B) The postoperative temperatures of the left feet skin 2 weeks (n = 12) and 7 weeks (n = 8) after sympathectomy. No significant differences in hind left plantar skin temperature or sacrococcygeal skin temperature were found among groups or at different time points (P > 0.05). Data are expressed as the mean ± SD (one-way analysis of variance and the least significant difference test).

Figure 4

Effect of lumbar sympathectomy on the sweating of the plantar skin of the hind feet. Negative staining: Blue sweat spots in the plantar skin of hind feet were not different from those in the plantar skin of front feet in the rats without sympathetic denervation. Positive staining: Blue sweat spots in the plantar skin of hind feet were fewer than those in the plantar skin of front feet in the rats with lumbar sympathetic denervation.

Figure 5

Immunohistochemical staining of norepinephrine under a light microscope in the plantar skin of hind feet 2 weeks and 3 months after sympathectomy in rats. At 2 weeks, the positive staining of norepinephrine in the sympathectomized group was less than that in the normal group. Arrows indicate positive staining within sympathetic neurons. Scale bars: 100 μm.

Figure 6

Immunohistochemical staining of dopamine β-hydroxylase under a light microscope in the plantar skin of hind feet 2 weeks and 3 months after sympathectomy in rats. At 2 weeks, the positive staining of dopamine β-hydroxylase in the sympathectomized group was less than that in the normal group. Arrows indicate positive staining within sympathetic neurons. Scale bars: 100 μm.

Figure 7

Protein expression of NE and DβH in the plantar skin of hind feet 2 weeks and 3 months after sympathectomy in rats. (A) NE and DβH protein bands of western blot assays. (B) Expressions of NE in the plantar skin of hind feet. NE expression was significantly lower in the sympathectomized group compared with the normal group and sham-operated group at 2 weeks. NE expression levels were not different among groups at 3 months. (C) Expressions of DβH in the plantar skin of hind feet. DβH expression was significantly lower in the sympathectomized group compared with the normal group and sham-operated group at 2 weeks. DβH levels were also not different among the groups at 3 months. Protein levels were calculated relative to the GAPDH level in the same sample. Data are expressed as the mean ± SD (n = 4 specimens per group at each time point). Each experiment was conducted in triplicate, and the results were averaged for the evaluation of the experimental results. *P < 0.05, vs. sympathectomized group (one-way analysis of variance and the least significant difference test). NE: Norepinephrine; DβH: dopamine β-hydroxylase.

Figure 8

Immunohistochemical staining of norepinephrine under a light microscope in sacrococcygeal skin 2 and 7 weeks after sympathectomy in rats. At 2 weeks, the positive staining of norepinephrine in the sympathectomized group was less than that in the normal group. Arrows indicate positive staining within sympathetic neurons. Scale bars: 100 μm.

Figure 9

Immunohistochemical staining of dopamine β-hydroxylase under a light microscope in sacrococcygeal skin 2 and 7 weeks after sympathectomy in rats. At 2 weeks, the positive staining of dopamine β-hydroxylase in the sympathectomized group was less than that in the normal group. Arrows indicate positive staining within sympathetic neurons. Scale bars: 100 μm.

Figure 10

Expression of NE and DβH in sacrococcygeal skin 2 and 7 weeks after sympathectomy in rats. (A) NE and DβH protein bands of western blot assay. (B) Expressions of NE in sacrococcygeal skin. NE expression was significantly lower in the sympathectomized group compared with the normal group and sham-operated group at 2 weeks. NE expression levels were not different among the groups at 7 weeks. (C) Expressions of DβH in sacrococcygeal skin. DβH expression was significantly lower in the sympathectomized group compared with the normal group and sham-operated group at 2 weeks. DβH levels were not different among the groups at 7 weeks. Protein levels were calculated relative to the GAPDH level in the same sample. Data are expressed as the mean ± SD (n = 4 specimens per group at each time point). Each experiment was conducted in triplicate, and the results were averaged for the evaluation of the experimental results. *P < 0.05, vs. sympathectomized group (one-way analysis of variance and the least significant difference test). NE: Norepinephrine; DβH: dopamine β-hydroxylase.

Figure 11

Effects of lumbar sympathectomy on the ultrastructure of L₅ sympathetic trunks of rats (transmission electron microscopy, uranyl acetate staining). (A) Sympathetic cells in the sham-operated group show integral myelin of axons and no perinuclear space. (B) Demyelination of axons and perinuclear space in sympathetic cells (arrows) were found in the sympathectomized group, 3 months post-surgery. Scale bars: 2 μm.