| Abstract No.: | C-D3151 |
| Country: | Venezuela |
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| Title: | REDUCED GABA NEUROTRANSMISSION UNDERLIES HYPERALGESIA
INDUCED BY REPEATED FORCED SWIMMING STRESS |
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| Authors/Affiliations: | 2 Ricardo Cárdenas*; 2 Lorena Leal; 2 José Antonio Silva; 1 Lorena Piñerua-Shuhaibar; 2 Luis Quintero; 2 Heberto Suárez-Roca;
1 Department of Neurobiology, IVIC-Zulia, Maracaibo; 2 Sección de Neurofarmacología y Neurociencias, Instituto de Investigaciones Clínicas, Facultad de Medicina, LUZ, Maracaibo, Venezuela
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| Content: | Objectives: We determined if cutaneous hyperalgesia and pain-induced c-Fos overexpression in the spinal cord produced by repeated forced swimming (FS) stress in the rat were related to changes in GABA neurotransmission by studying spinal release of GABA and the effect of positive modulation of GABA-A receptors with diazepam.
Materials and methods: Male rats were daily submitted to 10–20 min of either forced swimming or sham swimming (SS) for 3 consecutive days. Two days later, spinal GABA release was estimated by in vivo microdialysis. In other set of rats, either diazepam (2 mg/kg, i.p.) or saline was administered 1 h before either SS or FS and inflammatory nociception was assessed with the formalin test; it was followed by removal of lumbar spinal cords for c-Fos immunocytochemistry.
Results: Basal and pain-evoked release of GABA in the spinal cord was lower in FS rats than in SS rats. In contrast, pain scores during formalin test late phase and pain-induced c-Fos expression in laminae I–VI of ipsilateral dorsal horn were significantly higher in FS rats than in SS rats. In FS rats, diazepam did not have effect on GABA release but reduced pain scores and overexpression of c-Fos whereas flumazenil (0.1 mg/kg, i.p.), an antagonist of the benzodiazepine binding site, reversed these effects. When diazepam was given only 1 h before the formalin test, it slightly but significantly reduced pain scores during late phase in FS rats but not in SS rats.
Conclusion: Stress-induced reduction in GABA-A receptor activation is involved in the development of FS stress-induced hyperalgesia. |
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