Maria Caterina Pace

Neurobiology of pain

The neurobiology of pain had a notable interest in research focused on the study of neuronal plasticity development, nociceptors, molecular identity, signaling mechanism, ionic channels involved in the generation, modulation and propagation of action potential in all type of excitable cells. All the findings open the possibility for developing new therapeutic treatment. Nociceptive/inflammatory pain and neuropathic pain represent two different kinds of persistent chronic pain. We have reviewed the different mechanism suggested for the maintenance of pain, like descending nociceptive mechanism and their changes after tissue damage, including suppression and facilitation of defence behavior during pain. The role of these changes in inducing NMDA and AMPA receptors gene expression, after prolonged inflammation is emphasized by several authors. Furthermore, a relation between a persistent pain and amygdale has been shown. Molecular biology is the new frontier in the study of neurobiology of pain. Since the entire genome has been studied, we will able to find new genes involved in specific condition such as pain, because an altered gene expression can regulate neuronal activity after inflammation or tissue damage. J. Cell. Physiol. 209: 8–12, 2006.

Endocrine consequences of opioid therapy

Gonadal hormones are known to be affected by morphine and other opioids. In this paper, we summarize data collected in recent years which clearly indicate that the opioid-induced effects on steroid hormones depend on the opioid used and in some cases on the sex of the subject. Indeed morphine is able to reduce hormones like testosterone and cortisol in both male and female subjects in just a few hours, probably acting directly on peripheral glands. These depressant effects of morphine on hormones are also present in the treatment of surgical pain and are quickly reversible once opioid administration is suspended. Similar actions were also found to occur in experimental animals and in vitro in glial cells, further confirming the morphine-induced reduction of testosterone cell content. Testosterone and its metabolites are well known substances involved in the development and maintenance of the brain and all body structures. Thus when treating pain with opioids, their effects on hypothalamo-pituitary-gonadal and hypothalamo-pituitary-adrenal-related hormones must be considered and, where possible, hormone replacement therapy should be started.

Control of post-thoracotomy pain by transcutaneous electrical nerve stimulation: effect on serum cytokine levels, visual analogue scale, pulmonary function and medication

OBJECTIVES Transcutaneous electrical nerve stimulation (TENS) has been used to control post-thoracotomy pain with contrasting results. We aimed to assess the efficacy of TENS on post-thoracotomy pain in relation of four criterion measurements as: (i) cytokines; (ii) pain; (iii) respiratory function and (iv) intake of narcotic medication. METHODS Between January 2008 and October 2010, 58 patients underwent standard posterolateral thoracotomy for resectable lung cancer. Fifty patients were enrolled in the present study and randomized in two groups: TENS group (25 patients) who received postoperatively TENS for 5 days and placebo group (25 patients) without TENS. In both groups (i) serum cytokines (IL-6, IL-10, TNF-α) were measured by ELISA before surgery and at 6, 12, 24, 48, 72, 96 and 120 postoperative hours (POHs); (ii) at the same POHs, the pain score was measured using visual analogue scale (VAS) ranging from 0 to 10 levels; (iii) respiratory function (FEV 1% and FVC % of predicted value) were valuated on 72, 96 and 120 POHs; (iv) the total intake of narcotic medication given during postoperative period of 5 days was recorded. Repeated measures of analysis of variance assess the difference between two study groups. A value of P < 0.05 was considered statistically significant. RESULTS Of the 50 patients enrolled, two patients of TENS group and two patients of the placebo group were lost to follow-up. (i) Serum IL-6 (P = 0.001), IL-10 (P = 0.001) and TNF-α (P = 0.001) levels in TENS group were significantly lower than in the control group; (ii) VAS score in TENS group was significantly lower than in the control group (P < 0.001); (iii) recovery of FEV 1 (P = 0.02) and of FVC (P = 0.02) was statistically better in the TENS group than in control group; (iv) morphine requirement was lower in the TENS group with respect to placebo TENS (P = 0.004). After 48 POHs, no patient required supplementary dose of morphine. TENS group compared with placebo-group presented a significant reduction of non-opioid consumption (P = 0.002). CONCLUSIONS TENS is a valuable strategy to alleviate post-thoracotomy pain with reduction of cytokine production and of analgesic consumption, and with positive effects on pulmonary ventilation function.

Ionic channels and neuropathic pain: Phisiopatology and applications

Neuropathic pain is defined by the International Association for Pain research as a pain associated to a primary lesion or a dysfunction of the central or peripheral system. Over the past few years the causes of the neuropathic pain were not known and there were not good treatments for it, now we have a better knowledge of the physiopathological aspects and there is a wider diffusion of the research for target aimed therapies. The physiologic genesis of nervous messages occurs exclusively in skin sensorial endings or in nerve tissues as a consequence of an adequate sensorial stimulus and depends on the quick variations of the electric potential difference at the endings of ionic membranes. These variations of even 500 V a second are possible because of the presence of ionic channels. In neuropathic pain impulses can be originated even from ectopic sites. Ectopic discharges originated in a peripheral neuropathic system have an important role in the early stage of neuropathic pain development in two different ways. First they give an excess of spontaneous and evoked electric impulses to the central nervous system, causing a primitive neuropathic pain signal; then the ectopic activity develops and maintains the central sensitisation process. All this amplifies the afferent signals deriving from residual efferents that go on innerving cutaneous areas damaged and partly disnerved, causing tactile allodynie. Sodium channels are the greatest responsible for electrogenesis, that is the basis of the action potential generation and its propagation. Action potential begins after a depolarization such that it could cause a membrane transitory modification, turning prevalently permeable to Na+ more than to K+ as during a release phase. Neuropathy generates a local accumulation of sodium channels, with a consequent increase of density. This remodel seems to be the basis of neuro hyperexecitably. Calcium channels have also an important role in cell working. Intracellular calcium increase contributes to depolarization processes, through kinase and determines the phosphorylation of membrane proteins that can make powerful the efficacy of the channels themselves. In the future new diagnostic opportunities of physiopathologist mechanism leading to neuropathic pain will allow treatments aimed at specific molecular changes of ionic channels. J. Cell. Physiol. 215: 8–14, 2008.

Buprenorphine in long-term control of chronic pain in cancer patients.

The aim of this randomized open-label prospective study was to evaluate the analgesic activity of buprenorphine in a transdermal formulation for cancer chronic pain control versus sustained-release morphine, in all cases combined with oral tramadol. A transdermal system with 35 microg/h buprenorphine was applied to the first group of patients (BT); the second group received 60 mg/day of sustained-release morphine (MT). In both groups oral tramadol was administered to a maximum of 200 mg daily, in case of need. The administration of transdermal buprenorphine versus morphine resulted in significant differences in the physical pain (P = 0.01), mental health (P = 0.03) and vitality (P = 0.001). These data indicated that the BT group showed an improvement of pain and a positive effect on the quality life.

Estradiol and testosterone differently affect visceral pain-related behavioural responses in male and female rats

In the study of pain, the presence of sex differences is well known, with female subjects being more affected in a number of chronic painful conditions; however, the underlying mechanisms and the involvement of gonadal hormones, are still controversial. This study evaluated visceral pain in a validated rat model of artificial calculosis and the effects of estradiol and testosterone administration. Adult male and female rats were divided into groups and treated with one of the substances or Oil (vehicle) for 5 days, starting 2 days before surgery, with half receiving an artificial calculosis (Stone) and half only a sham (Sham) procedure. The animals’ behaviour (ureteral crises, frequency and duration) were recorded for 72 h; estradiol and testosterone plasma levels were determined in all groups at the end of the observation period. After surgery, only Stone rats showed ureteral pain crises, with a significant sex difference in the Oil‐treated groups in which the number and duration of crises were higher in females than in males. This difference was not present in the estradiol‐treated groups in which ureteral crises were decreased only in females while testosterone treatment had no effect in either sex. Estradiol and testosterone plasma levels were affected by treatments in both sexes. These results confirm that, also in this model of visceral pain, females experience more pain than males; moreover, they show that supraphysiological levels of estradiol, but not of testosterone, are analgesic only in females. A dose and sex‐dependent efficacy of gonadal hormones is suggested and discussed.

Metabolic syndrome is associated with a poor outcome in patients affected by outflow tract premature ventricular contractions treated by catheter ablation

BackgroundThe purpose of this study was to investigate the impact of metabolic syndrome (MS) on outcome of catheter ablation (CA) for treatment of frequent premature ventricular contraction beats (PVCs) originating from right ventricular outflow tract (RVOT), left ventricular outflow tract (LVOT) or coronary cusps (CUSPs), in patients with normal ventricular systolic function and absence of cardiac structural disease.MethodsIn this multicentre prospective study we evaluated 90 patients with frequent PVCs originating from RVOT (n = 68), LVOT (n = 19) or CUSPs (n = 3), treated with CA. According to baseline diagnosis they were divided in patients with MS (n = 24) or without MS (n = 66). The study endpoint was a composite of recurrence of acute or delayed outflow tract ventricular arrhythmia: acute spontaneous or inducible outflow tract ventricular arrhythmia recurrence or recurrence of outflow tract PVCs in holter monitoring at follow up.ResultsPatients with MS compared to patients without MS showed a higher acute post-procedural recurrence of outflow tract PVCs (n = 8, 66.6%, vs. n = 6, 9.0%, p = 0.005). At a mean follow up of 35 (17-43) months survival free of recurrence of outflow tract PVCs was lower in patients with baseline MS compared to patients without MS diagnosis (log-rank test, p < 0.001). In cox regression analysis, only MS was independently associated with study endpoint (HR = 9.655 , 95% CI 3.000-31.0.68 , p < 0.001).ConclusionsMS is associated with a higher recurrence rate of outflow tract PVCs after CA in patients without structural heart disease.

Effects of Vaginal Progesterone on Pain and Uterine Contractility in Patients with Threatened Abortion before Twelve Weeks of Pregnancy

Abstract: Fifty women with previous diagnosis of inadequate luteal phase and threatened abortion underwent a prospective, randomized, double‐blind study in one medical center carried out with a parallel trial. The primary objective was to establish the effects of vaginal progesterone (Crinone 8%) in reducing both pain and uterine contractions (UCs). The gel with or without (placebo) vaginal progesterone was administered once a day since the diagnosis of threatened abortion and for 5 days. The efficacy on pain symptom amelioration was evaluated by a 5‐score intensity gradation, while the UCs were evaluated by ultrasound. The secondary objective of the study was to evaluate the outcome of the pregnancies. The use of progesterone was effective both on pain relief and on the frequency of the UCs that decreased after 5 days of vaginal progesterone administration (P < 0.005). The evaluation of the ongoing pregnancy and spontaneous abortion in both study groups after 60 days showed that 4 patients of group A and 8 patients of group B miscarried (P < 0.05). In conclusion, patients with threatened abortion benefit from vaginal progesterone by a reduction of UCs and pain. The use of vaginal progesterone improved the outcome of pregnancies complicated by threatened abortion and previous diagnosis of inadequate luteal phase.

Pregabalin and transcutaneous electrical nerve stimulation for postherpetic neuralgia treatment.

ObjectivePostherpetic neuralgia (PHN) is responsible for one of the most common types of neuropathic pain, described as a burning pain that shakes, hits, and tightens and includes allodynia and paresthesia. Aim of the StudyTo evaluate the efficacy of Pregabalin when used during transcutaneous electric nerve stimulation (TENS) in patients with PHN and to analyze any changes in physical activity and sleep quality. MethodsPatients aged 50 to 80 years were included in this randomized study. We enrolled 15 male (average age 65±8.6 y) and 15 female patients (average age 64±8.2 y). The male patients had a history of neuropathic pain lasting 15.6±8.8 months whereas the female patients had a history of neuropathic pain lasting about 14.9±8.6 months. We began with 1 week of patient screening followed by a week of Pregabalin titration. Then, we established the dose of Pregabalin for each patient to obtain visual analog scale (VAS) of less than 60 mm. The eligible patients were randomly divided into 2 groups receiving Pregabalin + TENS or Pregabalin+TENS placebo for the following 4 weeks. Patients underwent 8 outpatient visits during which they completed VAS, SF-McGill Pain Questionnaire, and sleep interference questionnaire. ResultsThe resulting data showed that Pregabalin administration associated with TENS reduced pain in patients with PHN. At the end of the treatment, all the observed groups presented a reduction of mean VAS. The group treated with Pregabalin 300 (P300)+TENS had a reduction of pain of 30% and the group treated with Pregabalin 600 (P600)+TENS had a reduction of pain of 40%. The comparison between group P300+TENS versus group P300+TENS placebo showed a statistically significant reduction of VAS (P300+TENS 25±0.67 vs. P300+TENS placebo 39±1.19 P<0.02). Moreover, the comparison between group P600+TENS versus group P600+TENS placebo has shown a statistically significant reduction of VAS (P600+TENS 23±0.78 vs. P600+TENS placebo 32±0.81 P<0.02). At the end of the study, all groups showed a statistically significant difference in terms of sleep interference, Short-Form McGill Pain Questionnaire total score, and Short-Form McGill Pain Questionnaire Present Pain Intensity. ConclusionsThese data support the conclusion that Pregabalin gives better results when combined with TENS therapy, which is an analgesic nonpharmacologic procedure. Therefore, a multidisciplinary treatment should be considered for this kind of pain.

Opioids Switching with Transdermal Systems in Chronic Cancer Pain

BackgroundDue to tolerance development and adverse side effects, chronic pain patients frequently need to be switched to alternative opioid therapyObjectiveTo assess the efficacy and tolerability of an alternative transdermally applied (TDS) opioid in patients with chronic cancer pain receiving insufficient analgesia using their present treatment.MethodsA total of 32 patients received alternative opioid therapy, 16 were switched from buprenorphine to fentanyl and 16 were switched from fentanyl to buprenorphine. The dosage used was 50% of that indicated in equipotency conversion tables. Pain relief was assessed at weekly intervals for the next 3 weeksResultsPain relief as assessed by VAS, PPI, and PRI significantly improved (p < 0.0001) in all patients at all 3 follow up visits. After 3 weeks of treatment, the reduction in the mean VAS, PPI, and PRI scores in the fentanyl and buprenorphine groups was 68, 77, 74, and 69, 79, and 62%, respectively. Over the same time period the use of oral morphine as rescue medication was reduced from 27.5 ± 20.5 (mean ± SD) to 3.75 ± 8.06, and 33.8 ± 18.9 to 3.75 ± 10.9 mg/day in the fentanyl and buprenorphine groups, respectively. There was no significant difference in either pain relief or rescue medication use between the two patient groups The number of patient with adverse events fell during the study. After the third week of the treatment the number of patients with constipation was reduced from 11 to 5, and 10 to 4 patients in the fentanyl and buprenorphine groups, respectively. There was a similar reduction in the incidence of nausea and vomiting. No sedation was seen in any patient after one week of treatment.ConclusionOpioid switching at 50% of the calculated equianalgesic dose produced a significant reduction in pain levels and rescue medication. The incidence of side effects decreased and no new side effects were noted. Further studies are required to provide individualized treatment for patients according to their different types of cancer.