The magnitude of mechanical allodynia in a rodent model of lumbar radiculopathy is dependent on strain and sex.
METHODS
This study examined the differences in tactile hypersensitivity across 6 different strains of male mice, and between male and female rats of 3 different strains in a rodent model of low back pain associated with lumbar radiculopathy.


OBJECTIVE
We investigated the possibility that differences in tactile allodynia following the same nerve root injury are affected by genotype and sex in rodents.


BACKGROUND
Low back pain associated with radiculopathy affects countless people throughout the world, encompassing a wide range of individual pain susceptibility. The roles of genetics and sex on differences in nociceptive sensitivities following lumbar nerve root injury have yet to be fully characterized.


METHODS
Six strains of mice (BALB/cJ, CBA/J, C57BL/6J, 129P3/J, C3H/HeJ, and C58/J; all males) and male and female Sprague Dawley, Holtzman, and Long-Evans rats underwent a lumbar nerve root injury followed by assessment of tactile allodynia.


RESULTS
The most sensitive mouse strains following nerve root injury were: 129P3/J, C58/J, and BALB/cJ; and the less sensitive strains were: C57BL/6J, C3H/HeJ, and CBA/J. Female Sprague Dawley and Long-Evans rats displayed increased hypersensitivity following nerve root injury compared to males. No sex differences were observed in Holtzman rats.


CONCLUSIONS
Different mouse strains, and male and female rats that are exposed to identical nerve root injuries have diverse levels of tactile hypersensitivity, supporting the hypothesis that genetic factors and sex play a key role in radicular pain. Our results correlate with data compiled in identical mouse and rat strains after L5-L6 nerve ligation, suggesting that the precise nature of the injury is not relevant to the inheritance of neuropathic symptom sensitivity.
LaCroix-Fralish
Michael L
ML
Department of Pharmacology and Toxicology, Dartmouth College, Hanover, NH, USA.
Rutkowski
Maria D
MD
Weinstein
James N
JN
Mogil
Jeffrey S
JS
Deleo
Joyce A
JA
D000818:Animals; D005260:Female; D006930:Hyperalgesia / Q000209:etiology* / Q000503:physiopathology*; D008161:Lumbosacral Region; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D010812:Physical Stimulation; D051381:Rats; D012727:Sex Characteristics; D013045:Species Specificity; D013126:Spinal Nerve Roots / Q000293:injuries*; D014110:Touch; D014947:Wounds and Injuries / Q000150:complications