Cerebrospinal fluid in acquired immunodeficiency syndrome

Abstract

Pain is responsible for most of patients complaints. The mechanisms involved in chronic pain are still unknown and they are object of intensive studies. Recently, important steps in this area have been done thanks to the use of new animal models of chronic pain, this way bringing further contribution for therapeutical approaches.Among pain modalities, the neuropathic pain is not yet well known. Anticonvulsants have been used in its treatment with partial success.With the aim of contributing for the understanding and alleviation of the human neuropathic pain syndromes we have tried to study the effect of vigabatrin, a new gabaergic anticonvulsant, in an animal model of chronic neuropathic pain, described by Bennet and Xie (1988) and modified by Seltzer (1990).For this, 36 Wistar rats divided in 2 experimental groups (n=20), and 2 control groups (normal rats, n=8; and sham-operated rats, n=8) were used. As pain parameters, we have used the spontaneous scratching behavior, suggestive of chronic pain, and the latency of hindlimbs withdrawal and struggle reaction to nocive thermal stimuli (46ºC).The behavioral results showed a chronic significant (p<0.05) increase of the scratching behavior and the presence of allodynia as shown by the thermal test in the experimental animals. Vigabatrin was effective in diminishing significantly (p<0.05) the scratching behavior in a dose-dependent way as well as in reverting significantly (p<0.05) the allodynia in those animals. This vigabatrin effect was not, however, reverted by naloxone, excluding this way an opioid participation in it. Moreover, the valproate acid, as a gabaergic, and other classical anticonvulsants with analgesic properties in neuropathic pain (carbamazepine and phenitoin) have corroborated the analgesic effect of vigabatrin.This study leads to the conclusion that vigabatrin may possibly exert an analgesic effect on chronic neuropathic pain. Further studies are however needed to confirm these preliminary results.