Hugo Adriaensen

Morphine differentially affects the sensory and affective pain ratings in neurogenic and idiopathic forms of pain

&NA; In a double‐blind, placebo controlled crossover study, the effect of morphine on the affective and sensory pain ratings in different forms of chronic pain was investigated. Six patients suffering from central neurogenic pain, 8 from peripheral neurogenic pain and 6 from idiopathic pain participated in the study. Morphine (0.3 mg/kg bodyweight) and placebo (saline) were administered intravenously. Both the affective and sensory dimensions of pain sensation were assessed by means of the 101‐point rating scale. From our results it appeared that morphine reduced the affective but not the sensory dimension of pain sensation in both groups of neurogenic pain patients. In the idiopathic pain group, neither the affective nor the sensory dimension of pain sensation were affected. The observed differences in opioid responsiveness were neither the result of differences in opioid consumption nor of differences in baseline pain levels.

The mcgill pain questionnaire constructed for the dutch language (mpq-dv) - preliminary data concerning reliability and validity

&NA; The Dutch version of the McGill Pain Questionnaire was composed mainly by following R. Melzacks methodological design. The recommendations of the Finnish research team were considered and integrated. In the first phase as wide an inventory of pain descriptions as possible was drawn up. In the second phase, these pain descriptions were categorized by pain experts and students according to quality aspects. In the third phase, the pain descriptions were judged according to intensity aspect as well by pain experts, by students and by pain patients. Finally a fourth phase was set up to obtain insight into the reliability and validity of the McGill Pain Questionnaire ‐ Dutch Version (MPQ‐DV).

Behavioral assessment of facial pain in rats : face grooming patterns after painful and non-painful sensory disturbances in the territory of the rat's infraorbital nerve

&NA; Noxious stimulation of the rats face evokes intense face grooming with face wash strokes almost exclusively directed to the stimulated area (e.g. Clavelou et al., Neurosci. Lett., 14 (1989) 3263–3270). Similar asymmetric face grooming behavior has been observed after transection (Berridge and Fentress, J. Neurosci., 6 (1986) 325–330) and chronic constriction of the infraorbital nerve (Vos et al., J. Neurosci., 14 (1994) 2708–2723). In the present study, the relation between unilateral facial pain and asymmetric face grooming was experimentally studied in normal, intact rats: face grooming patterns evoked by non‐painful sensory disturbances in the territory of the infraorbital nerve (i.c. unilateral vibrissae clipping, anesthetic infraorbital nerve blockade, application of mineral oil on vibrissae) were compared to those evoked by noxious facial stimulation (s.c. formalin injection in mystacial pad) and those observed in unstimulated control rats, using video‐analysis. Only formalin‐injected rats displayed significantly more face grooming activity directed to the affected infraorbital nerve territory than unstimulated control rats. Non‐painful sensory disturbances (especially mineral oil application) induced an initial bout of directed face grooming; this response was transient and short‐lasting. These observations suggest that directed face grooming can be used as a sign of unilateral facial pain in freely moving rodents; unilateral non‐painful facial sensory disturbances do not lead to intense and persistent directed face grooming.

The emotional stroop task and chronic pain: what is threatening for chronic pain sufferers?

Using a computer version of the emotional stroop task, it was investigated whether chronic pain patients display an involuntary attentional shift towards pain‐related information (sensory, affective pain words and injury related words). Multiple regression analyses were used to investigate which pain and psychosocial variables (pain severity, pain‐related fear, pain catastrophizing and negative affect) were predictive of attentional bias. Results indicated: (1) that there was an attentional bias towards the sensory pain words; and (2) that current pain intensity was predictive of the effect. No other attentional effects were found. The results are discussed in terms of possible reasons for the difficulty of demonstrating attentional bias in chronic pain patients. Copyright 2000 European Federation of Chapters of the International Association for the Study of Pain

Comparison of epidural sufentanil plus clonidine with sufentanil alone for postoperative pain relief

Sufentanil 25 μg plus clonidine 1 μg/kg administered epidurally was compared with epidural sufentanil 50 μg alone in a double‐blind fashion for pain relief in 40 patients after abdominal surgery. The duration of complete pain relief was significantly longer in those who received the mixture. Oxygen saturation was reduced 10 and 20 minutes after sufentanil alone, but remained stable after sufentanil and clonidine. There were significant decreases in arterial blood pressure in the latter group that were maximum between 20 and 120 minutes after administration.

Critical review of oral drug treatments for diabetic neuropathic pain-clinical outcomes based on efficacy and safety data from placebo-controlled and direct comparative studies.

The present review aims to evaluate the efficacy and safety of a selection of oral treatments for the management of painful diabetic neuropathy. A literature review was conducted retrieving placebo‐controlled and direct comparative studies with a selection of oral treatments for painful diabetic neuropathy. All studies were analyzed with regard to efficacy and tolerability. Efficacy was evaluated as the percentage improvement in pain intensity between baseline and endpoint. Tolerability was evaluated by means of study discontinuations due to adverse events and by incidence of drug‐related adverse events.

The 5-HT1A receptor agonist F 13640 attenuates mechanical allodynia in a rat model of trigeminal neuropathic pain

The effects of acute intraperitoneal injections of the 5-HT(1A) receptor agonists F 13640 [(3-chloro-4-fluoro-phenyl)-[4-fluoro-4-[[(5-methyl-pyridin-2-ylmethyl)-amino]-methyl]piperidin-1-yl]-methadone] and F 13714 [3-chloro-4-fluorophenyl-(4-fluoro-4-[[(5-methyl-6-methylamino-pyridin-2-ylmethyl)-amino]-methyl]-piperidin-1-yl-methanone] were studied in comparison with those of baclofen and morphine on responsiveness to von Frey hair stimulation after chronic constriction injury to the rats infraorbital nerve (IoN-CCI). Following IoN-CCI, an ipsilateral hyperresponsiveness developed that remained stable in control rats throughout the period of drug testing. F 13640, F 13714, baclofen and morphine dose-dependently decreased the hyperresponsiveness; normalization of the response occurred at doses 0.63, 0.04, 5 and 10 mg/kg, respectively. Confirming earlier data, baclofens effects further validate IoN-CCI as a model of trigeminal neuralgia. The effects of F 13640 and F 13714 are initial evidence that 5-HT(1A) receptor agonists produce profound analgesia in the IoN-CCI model. The present data extend recent evidence that high-efficacy 5-HT(1A) receptor activation constitutes a new mechanism of central analgesia the spectrum of which may also encompass trigeminal neuropathic pain.

Influence of thiopental, etomidate, and propofol on regional myocardial function in the normal and acute ischemic heart segment in dogs

The effects of 30-min infusions of thiopental (20, 30, 40, 50, 60 and 70 mg·kg−1·h−1), etomidute (2.4, 3.6, 7.2, 9.6, 12, and 14.4 mg·kg−1·h−1), and propofol (6, 9, 12, 15, 18, and 21 mg·kg−1·h−1) On regional hemodynamic variables In the normal and acute ischemic heart segment were studied in dogs using ultrasonic segment length gauges. The three agents were associated with a dose-dependent decrease in end-diastolic length, indicating u decrease in left ventricular filling. This effect was most pronounced for propofol. At the doses tested, etomidate did not significantly alter regional myocardial function. Thiopental, however, was associated with a dose-dependent decrease in systolic shortening, which was significantly greater in the ischemic segment. These findings confirm the hemodynamic stability seen with etomidate and show that thiopental depresses myocardial function more in the acute ischemic heart than in the normal heart. The decrease in systolic shortening associated with propofol was similar in the normal and in the acute ischemic heart segment.

Endothelin-1-induced pain and hyperalgesia: a review of pathophysiology, clinical manifestations and future therapeutic options.

Pain in patients with metastatic cancer contributes to increased suffering in those already burdened by their advancing illness. The causes of this pain are unknown, but are likely to involve the action of tumour-associated mediators and their receptors. In recent years, several chemical mediators have increasingly come to the forefront in the pathophysiology of cancer pain. One such mediator, endothelin-1 (ET-1), is a peptide of 21 amino acids that was initially shown to be a potent vasoconstrictor. Extensive research has revealed that members of the ET family are indeed produced by several epithelial cancerous tumours, in which they act as autocrine and/or paracrine growth factors. Several preclinical and clinical studies of various malignancies have suggested that the ET axis may represent an interesting contributor to tumour progression. In addition, evidence is accumulating to suggest that ET-1 may contribute to pain states both in humans and in other animals. ET-1 both stimulates nociceptors and sensitises them to painful stimuli. Selective stimulation of ET receptors has been implicated as a cause of inflammatory, neuropathic and tumoural pain. ET-1-induced pain-related behaviour seems to be mediated either solely by one receptor type or via both endothelin-A receptors (ETAR) and endothelin-B receptors (ETBR). Whereas stimulation of ETAR on nociceptors always elicits a pain response, stimulation of ETBR may cause analgesia or elicit a pain response, depending on the conditions. The administration of ETAR antagonists in the receptive fields of these nociceptors has been shown to ameliorate pain-related behaviours in animals, as well as in some patients with advanced metastatic prostate cancer. The identification of tumour-associated mediators that might directly or indirectly cause pain in patients with metastatic disease, such as ET-1, should lead to improved, targeted analgesia for patients with advanced cancer. In this review, we will describe the current status of the role of ET-1 in different types of painful syndromes, with special emphasis on its role in the pathophysiology of cancer pain. Finally, potential new treatment options that are based on the role of the ET axis in the pathophysiology of cancer are elaborated.

Epidural ketamine potentiates epidural morphine but not fentanyl in acute nociception in rats.

Epidural opioids have been reported to provide superior analgesia in acute pain management. Despite the fact that the required doses are low, major side effects such as respiratory depression may still occur. In an effort to maximize analgesia and to minimize the rate of side effects, epidural NMDA receptor antagonists, especially ketamine, may be co‐administered with opioids. This study investigated whether ketamine had beneficial effects on fentanyl‐ or morphine‐induced antinociception in an acute pain model in rats.