Table 1.
Effect of sympathectomy on neuropathic pain in the rat: summary of major studies in different experimental models
| Neuropathic pain model | sympX timing (related to nerve injury) | Type of sympX | Mechanical allodynia | Mechanical hyperalgesia | Heat hyper-sensitivity | Cold hyper-sensitivity |
| CCI | 5 d prior | Chemical GU | ↔(a) | ↘↘↘(a) | ↘↘↘(a) | |
| Intra-operative | Surgical | ↔/↗(b,1) | ↘↘(b) | ↘↘↘(b) | ||
| 1 w after | Surgical | ↘(k) | ↘(k) | |||
| 10 d after | Chemical GU | ↘(a) | ↘↘(a) | ↘↘↘(a) | ||
| PSL | 7 and 4 d prior | Chemical GU | ↔(c) | ↘(c) | ||
| Intra-operative | Chemical GU | ↗(c,2) | ↗(c,2) | |||
| 1 w after | Surgical | ↘(k) | ↘(k) | |||
| 7 m after | Chemical GU | ↘↘↘(c) | ↘↘↘(c) | |||
| SNL L5 or SNL L5/L6 | 1 w prior | Surgical | ↘↘↘(d), ↔(h) | ↘↘↘(d) | ||
| Intra-operative | Surgical | ↔(g) | ↘(f) | |||
| Intra-operative | Chemical GU/PM | ↔(g) | ||||
| 4 d after | Surgical | ↘↘↘(f) | ↘↘(d,e) | ↘(k), ↘↘↘(e) | ||
| 1 w after | Surgical | ↘↘↘(d,k,e,i), ↔(h), ↘↘(j) | ↘↘(d) | |||
| 2 w after | Chemical GU/PM | ↘↘(d) | ||||
| 3 w after | Surgical | ↘↘↘(d), ↔(h) | ||||
| 5 w after | Surgical | ↘↘↘(d) |
a [21], b [12], c [13], d [25], e [23], f [11], g [15], h [16], i [22], j [26], k [14]
(1)Sympathectomy induces hyperalgesia in sham animals or in contralateral hind paw, (2)Possible direct effect of Guanethidine
sympX: sympathectomy, m: month, w: week, d: day
CCI: Chronic Constriction Injury, PSL: Partial Sciatic Ligation; SNL: Spinal Nerve Ligation
Sympathectomy slightly decreases (↘), decreases (↘↘), almost abolishes (↘↘↘), has no effect (↔) or aggravates (↗) pain hypersensitivity after nerve injury.
For guanethidine monosulfate (GU) and phentolamine mesylate (PM) injections:
a [21]: subcutaneous injections of GU (30 mg/kg), during 4 consecutive days
c [13]: one or two intraperitoneal injections of GU (30 mg/kg)
d [25]: single intraperitoneal injection of GU (30 mg/kg) or PM (0.5 and 4 mg/kg)
g [15]: single intravenous injection of GU (30 mg/kg) or PM (4 mg/kg)