Affiliations: [a] Centro de Biofísica y Bioquímica del Instituto Venezolano de Investigaciones Científicas, IVIC, Caracas, Venezuela | [b] Centro de Biofísica y Neurociencias, CBN-UC, Facultad de Ciencias de la Salud, Universidad de Carabobo, Valencia, Venezuela | [c] Instituto de Ingeniería Biológica y Médica, Facultades de Ingeniería, Medicina y Biología, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, P.O. 7820436, Santiago de Chile, Chile
Correspondence:
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Corresponding author: A. Eblen-Zajjur, Instituto de Ingeniería Biológica y Médica, Facultades de Ingeniería, Biología y Medicina, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, P.O. 7820436, Santiago de Chile, Chile. Tel.: +56 9 44292800; E-mail: [email protected].
Abstract: Despite the frequent clinical hyper- or hypothermia cases, thermal-dependence of the endogenous pain modulation system at the spinal cord is not well understood. We evaluate spinal dorsal horn neuronal network responses during mechanical heterotopic noxious stimuli (HNS) at three different body temperatures (34; 37 or 40°C) by measuring lumbar cord dorsum potentials activated by electrical stimulation of the ipsilateral sural nerve in adult thiopental anesthetized rats. A noxious clamp was applied randomly to the tail, right hindpaw, right forepaw, muzzle and left forepaw. HNS induced a decrease of the N wave amplitude and duration at 37°C. This effect was reduced at 40°C for both amplitude (−18.2% for 37–40°C; P<0.0005) and duration (−16.4% for 37–40°C; P<0.0001). P wave did not show neither amplitude nor duration changes at neither 3 tested temperatures. Clinical range changes of temperature could modify pain sensation, moreover, hyperthermia increases nociceptive sensory input to dorsal horn, and could exacerbate pain sensation in individuals with fever.
