Neuropathic pain in aged rats: behavioral responses and astrocytic activation.

Neuropathic pain in aged rats: behavioral responses and astrocytic activation.

Stuesse S L; Crisp T; McBurney D L; Schechter J B; Lovell J A; Cruce W L

Experimental brain research

2001

2001-03

We used the Bennett and Xie (1988) model of chronic neuropathic pain to study the effect of age on thermal and tactile sensitivity and on astrocytic activation in the dorsal horn of the spinal cord after nerve injury. Fischer 344 FBNF1 hybrid rats in three age groups, 4-6, 14-16, and 24-26 months, were studied. Rats were either unligated (day 0, control) or the left sciatic nerve was loosely ligated to cause a chronic constriction injury (CCI). CCI causes a neuropathic pain condition characterized by tactile allodynia and thermal hyperalgesia. Rats were behaviorally assessed for tactile and thermal sensitivity of their ligated and unligated hind paws up to 35 days postligation. Rats were sacrificed before or at various days postligation, and activated astrocytes were identified at the L4-L5 levels of their spinal cords by use of an antibody to glial fibrillary acid protein (GFAP). The number of GFAP-ir astrocytes in the dorsal horn of the spinal cord in the control, uninjured condition decreased with age (P \textless or = 0.001) but increased after CCI in all three age groups. After CCI, astrocytic activation in the cord was less robust in aged rats than in younger ones (P \textless or = 0.01). Not all the CCI rats displayed hyperalgesia to touch and to heat. Rats with an increased sensitivity to heat had increased levels of GFAP-ir in their cords; however, rats with decreased thermal sensitivity also displayed increased

Aging/*physiology; Animal; Animal/*physiology; Animals; Astrocytes/*metabolism; Behavior; Cell Count; Disease Models; Functional Laterality/physiology; Glial Fibrillary Acidic Protein/metabolism; Hyperalgesia/physiopathology; Immunohistochemistry; Inbred F344; Lumbar Vertebrae; Male; Nerve Crush/methods; Neuralgia/*metabolism/pathology/physiopathology; Pain Measurement; Peripheral Nervous System Diseases/*metabolism/pathology/physiopathology; Posterior Horn Cells/*metabolism; Rats; Thermosensing/physiology; Touch/physiology; Up-Regulation/*physiology

Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).

219–227

2

137