Delayed sympathetic dependence in the spared nerve injury (SNI) model of neuropathic pain

Molecular Pain

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)

ISSN: 1744-8069