Preemptive analgesic effect of lidocaine in a chronic neuropathic pain model / Efeito analgésico preemptivo da lidocaína em modelo de dor crônica neuropática

Preemptive analgesia inhibits the progression of pain caused by surgical lesions. To analyze the effect of lidocaine on postoperative pain relief, we performed compression of the right sciatic nerve in Wistar rats and observed the differences on behavior between the group that received lidocaine and the group that was not treated with the local anesthetics pre-operatively. Group 1 was not operated (control); group 2 underwent the sciatic nerve ligature without lidocaine; group 3, underwent surgery with previous local infiltration of lidocaine. Group 2 showed significantly longer scratching times with a peak on day 14 post-operative (p=0.0005) and reduction in the latency to both noxious (p=0.003) and non-noxious (p=0.004) thermal stimulus. Group 3 presented significantly shorter scratching times (p=0.004) and longer latency times when compared to Group 2. Preemptive use of lidocaine 2 percent can potentially reduce the postoperative neuropathic pain associated with sciatic nerve compression.

A analgesia preemptiva inibe a progressão da dor causada por lesão cirúrgica. Para analisar o efeito da lidocaína na diminuição da dor pós-operatória, submetemos ratos Wistar a compressão cirúrgica do nervo ciático e observamos diferenças em alguns padrões de comportamento entre o grupo tratado com lidocaína pré-operatória e o grupo não-tratado com o anestésico local. O grupo 1 não foi operado (controle); o grupo 2, submetido a ligadura do nervo ciático sem lidocaína, apresentou significativo aumento do tempo de coçar-se com um pico no 14º pós-operatório (p=0.0005) e redução na latência para os estímulos térmicos nocivo (p=0.003) e não-nocivo (p=0.004); o grupo 3, operado com a droga preemptiva, demonstrou significativo decréscimo no tempo de coçar-se (p=0.004) e maiores tempos de latência quando comparados aos do grupo 2. O uso preemptivo da lidocaína 2 por cento pode, potencialmente, reduzir a dor neuropática pós-operatória associada à compressão do nervo ciático.

Motor neuron diseases in the University Hospital of Fortaleza (Northeastern Brazil): a clinico-demographic analysis of 87 cases

In this retrospective (1980-1998) study, we have analyzed clinico-demographically, from the records of the University Hospital of Fortaleza (Brazil), a group of 87 patients showing signs and symptoms of motor neuron diseases (MNDs). Their diagnosis was determined clinically and laboratorially. The WFN criteria were used for amyotrophic lateral sclerosis (ALS) diagnosis. The clinico-demographic analysis of the 87 cases of MNDs showed that 4 were diagnosed as spinal muscular atrophy (SMA), 5 cases as ALS subsets: 2 as progressive bulbar paralysis (PBP), 2 as progressive muscular atrophy (PMA) and 1 as monomelic amyotrophy (MA), and 78 cases of ALS. The latter comprised 51 males and 27 females, with a mean age of 42.02 years. They were sub-divided into 4 groups according to age: from 15 to 29 years (n= 17), 30 to 39 years (n= 18), 40 to 69 years (n= 39) and 70 to 78 years (n= 4). From the 78 ALS patients, 76 were of the classic sporadic form whilst only 2 were of the familial form. The analysis of the 87 patients with MNDs from the University Hospital of Fortaleza showed a predominance of ALS patients, with a high number of cases of juvenile and early onset adult sporadic ALS

Possible analgesic effect of vigabrin in animal experimental chronic neuropathic pain

Since anticonvulsants have been used for treating neuralgias, an interest has arisen to experimentally test vigabatrin for its gabaergic mechanism of action. For this, 41 Wistar rats were used, and in 25 of them a constractive sciatic neuropathy was induced (Bennet & Xie model). For testing pain symptoms, spontaneous (Scratching) and evoked behaviors to noxious (46 degrees Celsius) and non-noxious (40 degrees Celsius) thermal stimuli were quatified. Moreover, a comparative pharmacological study of vigabatrin with other analgesic anticonvulsant drugs was also performed. The results showed a possible dose-dependent analgesic effect of vigabatrin (gamma-vinyl-GABA) on experimental neuropathic pain, as shown vy the significant (p<0.05) decreasing effect of vigabatrin on scratching and by its significant (p>0.05) increasing effect on the latency of the right hindpaw withdrawal of the animals to noxious thermal stimulus. This was corroborated by similar findings with analgesic anticonvulsants (carbamazepine, phenytoin and valproic acid). This possible and not yet described analgesic effect of vigabatrin seems not to be opioid mediated.

Behavioral changes of Wistar rats with experimentally-induced painful diabetic neuropathy

With the purpose of studying data on spontaneous customary changes in diabetic rats, we induced diabetes in 28 Wistar rats with streptozotocin. The animals were observed for 27 weeks in an attempt to characterize spontaneous customary chages that could suggest signs of chronic pain. Morphine, as a central-acting potent analgesic and its specific antagonist naloxone, were used. Our results evidenced in the animals a clinical syndrome similar to human diabetes. Long-term customary analysis revealed a significant (p<0.05) increase of scratching and resting/sleeping behaviors, but diminished motor, eating and grooming customs. Moreover, the thermal tests revealed hyperalgesia in 43 per cent of the animals, what may corroborate the meaning of scratching as a sign of pain. Pharmacological tests with morphine showed a significant (p<0.05) inhibition of scratch, with concomitant increase of motor and eating activities and diminished rest/sleep capacity. Naloxone antagonized the effects induced by morphine. Such results suggest that these animals exhibit evoked behavior of hyperalgesia and that scratch may possibly be a spontaneous manifestation of chronic pain also in Wistar rats with this experimental model of painful diabetic neuropathy.

The effect of baclofen on spontaneous and evoked behavioral expression of experimental neuropathic chronic pain

Baclofen (Beta-p-chlorophenyl-GABA) has been used in humans to treat spasticity, as well as trigeminal neuralgia Since GABA (gamma-aminobutyric acid) has been implicated in inhibitory and analgesic effects in the nervous system, it was of interest to study the effect of baclofen in experimental neuropathic pain. With this purpose, experiments were carried out in 17 neuropathic rats with constrictive sciatic injury, as described by Bennet and Xie (1988), taking as pain parameters scratching behaviour and the latency to the thermal nociceptive stimulus. The results showed that baclofen induces, in a dose-dependent manner, significant decrease (p<0.05) of scratching behaviour and significant increase (p<0.05) of the latency to the nociceptive thermal stimulus. The absence of antagonism of naloxone suggested a non-participation of an opioid-mediated mechanism in this analgesic effect of baclofen on experimental neuropathic pain.

Amyotrophic lateral sclerosis: clinical analysis of 78 cases from Fortaleza (Northeastern Brazil)

We report on the clinical characteristics of amyotrophic lateral sclerosis (ALS) in Fortaleza (Northeastern Brazil). For this, we analyzed retrospectively (from 1980 to 1999) 78 cases of ALS from the Service of Neutrology of the University Hospital of Fortaleza diagnosed clinically and laboratorially (EMG, muscle biopsy, myelography, blood biochemistry, muscle enzymes and cranio-cervical X-ray). The results showed that they were mostly sporadic ALS (76/78), and they were divided into definite (n=36), probable (n=20), possible (n=15) and suspected (n=7), according to the level of diagnostic certainty. They were also subdivided into juvenile (n=17), early-onset adult (n=18), age-specific (n=39) and late-onset (n=4) groups. Clinically, they presented as initals symptoms, principally, asymmetrical (30/78) and symmetrical (24/78) weakness of extremities, besides bulbar signs, fasciculations, and atrophy. Curiously, pain as first symptom occurred in an expessive fashion (17/78). The predominant initial anatomic site, in this series, was the spinal cord, and mainly affecting the arms. As to the symptom accrual from region to region, this occurs more quickly in contiguous areas, and fasciculations are predominant when bulbar region was associated.