Involvement of Opioid Peptides in the Analgesic Effect of Spinal Cord Stimulation in a Rat Model of Neuropathic Pain / 神经科学通报·英文版

Spinal cord stimulation (SCS)-induced analgesia was characterized, and its underlying mechanisms were examined in a spared nerve injury model of neuropathic pain in rats. The analgesic effect of SCS with moderate mechanical hypersensitivity was increased with increasing stimulation intensity between the 20% and 80% motor thresholds. Various frequencies (2, 15, 50, 100, 10000 Hz, and 2/100 Hz dense-dispersed) of SCS were similarly effective. SCS-induced analgesia was maintained without tolerance within 24 h of continuous stimulation. SCS at 2 Hz significantly increased methionine enkephalin content in the cerebrospinal fluid. The analgesic effect of 2 Hz was abolished by μ or κ opioid receptor antagonist. The effect of 100 Hz was prevented by a κ antagonist, and that of 10 kHz was blocked by any of the μ, δ, or κ receptor antagonists, suggesting that the analgesic effect of SCS at different frequencies is mediated by different endorphins and opioid receptors.

Antinociception Induced by Moringa Stenopetela (Baker f.) Cufod. Leaves Extract and Possible Mechanisms of Action

Moringa stenopetala (Baker f.) Cufod., is an endemic species growing in the south of Ethiopia. M. stenopetala is often consumed as food and used in traditional medicine and it has also been traditionally used for relieving of pain in Ethiopia. This study aimed to investigate the antinociceptive effect and mechanisms of action of M. stenopetala leaves methanol extract in mice. The per-oral doses of 50, 100, and 200 mg/kg of M. stenopetala extract were tested for antinociceptive action by using hot-plate, tail-immersion, and writhing tests. The possible mechanisms of in the antinociceptive action were investigated by pre-treatment with 5 mg/kg naloxone (non-selective opioid antagonist), 1 mg/kg ketanserin (5-HT2A/2C receptor antagonist), and 1 mg/kg yohimbine (α2 adrenoceptor antagonist). The methanol extract of M. stenopetala showed antinociceptive effect in all tests. The significant involvement of 5-HT2A/2C receptors and α2 adrenoceptors in antinociception induced by M. stenopetala extract in the hot-plate and tail-immersion tests, as well as significant contribution of opioid receptors and α2 adrenoceptors in writhing test, were identified. In conclusion, these findings demonstrate that the methanol extract of M. stenopetala has potential in pain management. Thisstudywillcontributetonewtherapeuticapproachesandprovideguidancefornewdrug development studies.

Analysis of psychiatrists' prescription of opioid, benzodiazepine, and buprenorphine in Medicare Part D in the United States

Abstract Introduction The opioid epidemic is a severe problem in the world, especially in the United States, where prescription opioid overdose accounts for a quarter of drug overdose deaths. Objective To describe psychiatrists' prescription of opioid, benzodiazepine, and buprenorphine in the United States. Methods We conducted a retrospective cross-sectional study of the 2016 Medicare Part D claims data and analyzed psychiatrists' prescriptions of: 1) opioids; 2) benzodiazepines, whose concurrent prescription with opioids can cause overdose death; 3) buprenorphine, a partial opioid agonist for treating opioid addiction; 4) and naltrexone microsphere, a once-monthly injectable opioid antagonist to prevent relapse to opioid dependence. Prescribers with 11 or more claims were included in the analysis. Results In Medicare Part D in 2016, there were a total of 1,131,550 prescribers accounting for 1,480,972,766 total prescriptions and 78,145,305 opioid prescriptions, including 25,528 psychiatrists (2.6% of all prescribers) accounting for 44,684,504 total prescriptions (3.0% of all prescriptions) and 131,115 opioid prescriptions (0.2% of all opioid prescriptions). Psychiatrists accounted for 17.3% of benzodiazepine, 16.3% of buprenorphine, and 33.4% of naltrexone microsphere prescriptions. The opioid prescription rate of psychiatrists was much lower than that of all prescribers (0.3 vs 5.3%). The buprenorphine prescription rate of psychiatrists was much higher than that of all prescribers (2.3 vs. 0.1%). There was a substantial geographical variation across the United States. Conclusions The results show that, proportionally, psychiatrists have lower rates of opioid prescription and higher rates of benzodiazepine and buprenorphine prescription.

Naltrexone-associated Visual Hallucinations: A Case Report

Naltrexone is a competitive antagonist of μ, δ, and κ opioid receptors. Naltrexone has been investigated for use an as anti-obesity agent in both the general population and in patients with severe mental illness, including schizophrenia. In patients with schizophrenia, however, potential psychotic symptoms due to adverse effects of naltrexone have not been investigated. Our case study, a relevant case report, and some related articles suggest that naltrexone might be associated with the emergence of visual hallucinations, which clinicians should be aware of.

Opioid-induced constipation: a narrative review of therapeutic options in clinical management

Pain therapy often entails gastrointestinal adverse events. While opioids are effective drugs for pain relief, the incidence of opioid-induced constipation (OIC) varies greatly from 15% to as high as 81%. This can lead to a significant impairment in quality of life, often resulting in discontinuation of opioid therapy. In this regard, a good doctor-patient relationship is especially pivotal when initiating opioid therapy. In addition to a detailed history of bowel habits, patient education regarding the possible gastrointestinal side effects of the drugs is crucial. In addition, the bowel function must be regularly evaluated for the entire duration of treatment with opioids. Furthermore, if the patient has preexisting constipation that is well under control, continuation of that treatment is important. In the absence of such history, general recommendations should include sufficient fluid intake, physical activity, and regular intake of dietary fiber. In patients of OIC with ongoing opioid therapy, the necessity of opioid use should be critically reevaluated in terms of an with acceptable quality of life, particularly in cases of non-cancer pain. If opioids must be continued, lowering the dose may help, as well as changing the type of opioid. If these measures do not suffice, the next step for persistent OIC is the administration of laxatives. If these are ineffective as well, treatment with peripherally active μ-opioid receptor antagonists should be considered. Enemas and irrigation are emergency measures, often used as a last resort.

Analgesic effects of eucalyptus essential oil in mice

BACKGROUND: The use of aroma oils dates back to at least 3000 B.C., where it was applied to mummify corpses and treat the wounds of soldiers. Since the 1920s, the term “aromatherapy” has been used for fragrance therapy with essential oils. The purpose of this study was to determine whether the essential oil of Eucalyptus (EOE) affects pain pathways in various pain conditions and motor coordination. METHODS: Mice were subjected to inhalation or intraperitoneal injection of EOE, and its analgesic effects were assessed by conducting formalin, thermal plantar, and acetic acid tests; the effects of EOE on motor coordination were evaluated using a rotarod test. To determine the analgesic mechanism, 5′-guanidinonaltrindole (κ-opioid antagonist, 0.3 mg/kg), naltrindole (δ-opioid antagonist, 5 mg/kg), glibenclamide (δ-opioid antagonist, 2 mg/kg), and naloxone (μ-opioid antagonist, 4, 8, 12 mg/kg) were injected intraperitoneally. RESULTS: EOE showed an analgesic effect against visceral pain caused by acetic acid (EOE, 45 mg/kg); however, no analgesic effect was observed against thermal nociceptive pain. Moreover, it was demonstrated that EOE did not have an effect on motor coordination. In addition, an anti-inflammatory effect was observed during the formalin test. CONCLUSIONS: EOE, which is associated with the μ-opioid pain pathway, showed potential effects against somatic, inflammatory, and visceral pain and could be a potential therapeutic agent for pain.

Effects of Naloxegol on Gastrointestinal Transit and Colonic Fecal Volume in Healthy Participants Receiving Oxycodone

BACKGROUND/AIMS: Opioids cause gastrointestinal (GI) dysmotility, decrease gut secretion, and affect gut sphincters. Symptoms of opioid-induced bowel dysfunction may be alleviated by peripherally acting opioid antagonists like naloxegol, but detailed knowledge on GI effects of this drug is lacking. We hypothesized that naloxegol, compared to placebo, would reduce GI transit time and colonic fecal volume in opioid-treated healthy participants. METHODS: We conducted a randomized, double-blinded, single-center, 2-way cross-over study in 24 healthy males, randomized to a 6 day treatment period of oxycodone (15 mg twice a day) co-administered with either naloxegol (25 mg once a day) or matching placebo. Participants swallowed an electromagnetic capsule which determined GI transit times. Colonic fecal volume was quantified with magnetic resonance imaging both pre-treatment and post-treatment. RESULTS: Naloxegol reduced total GI transit time by 21% (56 hours vs 71 hours, P = 0.02) and colonic transit time by 23% (45 hours vs 59 hours, P < 0.01), compared to placebo. However, no difference in colonic fecal volume was found (818 mL vs 884 mL, P = 0.20). CONCLUSIONS: Short-term administration of naloxegol in healthy participants reverses the retardation of total GI and colonic transit induced by oxycodone. This supports the use of naloxegol in the treatment of GI side effects to opioid treatment, and add knowledge to the current understanding of mechanisms behind peripherally-acting opioid antagonists.

A Context-Based Analgesia Model in Rats: Involvement of Prefrontal Cortex / 神经科学通报·英文版

Cognition and pain share common neural substrates and interact reciprocally: chronic pain compromises cognitive performance, whereas cognitive processes modulate pain perception. In the present study, we established a non-drug-dependent rat model of context-based analgesia, where two different contexts (dark and bright) were matched with a high (52°C) or low (48°C) temperature in the hot-plate test during training. Before and after training, we set the temperature to the high level in both contexts. Rats showed longer paw licking latencies in trials with the context originally matched to a low temperature than those to a high temperature, indicating successful establishment of a context-based analgesic effect in rats. This effect was blocked by intraperitoneal injection of naloxone (an opioid receptor antagonist) before the probe. The context-based analgesic effect also disappeared after optogenetic activation or inhibition of the bilateral infralimbic or prelimbic sub-region of the prefrontal cortex. In brief, we established a context-based, non-drug dependent, placebo-like analgesia model in the rat. This model provides a new and useful tool for investigating the cognitive modulation of pain.

Colorectal Transit and Volume During Treatment With Prolonged-release Oxycodone/Naloxone Versus Oxycodone Plus Macrogol 3350

BACKGROUND/AIMS: Opioid-induced constipation (OIC) is the most common gastrointestinal (GI) side effect to opioid treatment. Opioid receptor antagonists against OIC have been introduced, but their efficacy has not been directly compared to conventional laxatives. Our aim was to compare symptoms and objective parameters of gut function in an experimental model of OIC during treatment with the opioid antagonist naloxone and oxycodone in prolonged-release (PR) formulation versus oxycodone plus macrogol 3350. METHODS: In this randomized, double-blind, crossover trial 20 healthy men received a 5-day treatment of combined PR oxycodone/naloxone or PR oxycodone plus macrogol 3350. Regional GI transit times and segmental colorectal transit were assessed with the Motilis 3D-Transit electromagnetic capsule system. Colorectal volumes were determined by MRI. OIC symptoms were assessed with validated questionnaires, along with stool frequency and consistency. RESULTS: Total colorectal volume did not change after 5 days’ treatment with PR oxycodone/naloxone (941 vs 1036 mL; P = 0.091), but increased significantly after PR oxycodone plus macrogol treatment (912 vs 1123 mL; P 0.05). The Patient Assessment of Constipation Symptom Questionnaire abdominal symptoms score was lower during PR oxycodone/naloxone compared to PR oxycodone plus macrogol (0.2 vs 3.2; P = 0.002). Stool frequency was lower during PR oxycodone/naloxone compared to PR oxycodone plus macrogol (4.2 vs 5.4; P = 0.035). CONCLUSIONS: PR oxycodone plus macrogol increases colorectal volume, but does not improve GI transit compared to PR oxycodone/naloxone. However, PR oxycodone/naloxone results in a lower abdominal symptom burden, despite higher stool frequency during macrogol treatment.

Differential expression of spinal γ-aminobutyric acid and opioid receptors modulates the analgesic effects of intrathecal curcumin on postoperative/inflammatory pain in rats

BACKGROUND: Curcumin is traditionally used as an herbal medicine. We explored the efficacy of intrathecal curcumin in relieving both postoperative and inflammatory pain and elucidated the mechanisms of action of curcumin interacting with γ-aminobutyric acid (GABA) and opioid receptors at the spinal level. METHODS: Experimental pain was induced in male Sprague-Dawley rats via paw incision or injection of intraplantar carrageenan. After examination of the effects of intrathecal curcumin on the pain, GABA and opioid receptor antagonists were intrathecally administered to explore the involvement of GABA or opioid receptors on the effect of curcumin. Additionally, the expression levels of the GABA and opioid receptors were assessed. RESULTS: Intrathecal curcumin reduced the withdrawal threshold of both incisional surgery- and carrageenan injection-induced nociception. Intrathecal GABA and opioid receptor antagonists reversed the curcumin-mediated antinociception. Incisional surgery decreased the levels of the GABA receptors mRNA, but little changed the levels of the opioid receptors mRNA. Carrageenan injection increased the levels of the opioid receptors mRNA, but not the GABA receptors mRNA levels. Intrathecal curcumin increased or decreased the levels of GABA receptors mRNA and opioid receptors mRNA in the spinal cords of incised or carrageenan-injected rats, respectively. CONCLUSIONS: Intrathecal curcumin was effective to postoperative and inflammatory pain and such antinociception of curcumin was antagonized by both GABA and opioid receptor antagonists. Also, intrathecal curcumin altered the levels of GABA and opioid receptors. Thus, spinal GABA and opioid receptors may, respectively, be directly or indirectly involved when curcumin alleviates postoperative and inflammatory pain.

Intrathecal tramadol may cause respiratory depression

Opioids such as morphine and fentanyl have been used in neuraxial anesthesia to prolong the analgesic effects since long, but these have frequently been associated with few adverse effects e.g. nausea, vomiting, pruritus and rarely respiratory depression. Tramadol has also been used in epidural as well as spinal anesthesia, and respiratory depression has not been reported with its intrathecal use. We present a case in which 20 mg of intrathecal tramadol produced signs of opioid overdose including respiratory depression. The side effects were reversed with naloxone confirming our suspicion that these were caused by tramadol. We recommend adequate monitoring and vigilance for tramadol as is used for other intrathecal opioids

µ-opioid receptors in the central nucleus of the amygdala regulate food rather than water intake in rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of µ-opioid receptors (µ-ORs) in the central nucleus of the amygdala (CeA) on feeding and drinking behaviors in rats and evaluate the role of glutamate signaling in opioid-mediated ingestive behaviors.</p><p><b>METHODS</b>Stainless steel cannulas were implanted in the unilateral CeA for microinjection of different doses of the selective µ-OR agonist DAMGO in satiated or water-deprived male SD rats. The subsequent food intake or water intake of the rats was measured at 60, 120, and 240 min after the injection. The rats receiving microinjections of naloxone (NTX, a nonselective opioid antagonist) or D-AP-5 (a selective N-methyl-D-aspartic acid-type glutamate receptor antagonist) prior to DAMGO microinjection were tested for food intake at 60, 120, and 240 min after the injections.</p><p><b>RESULTS</b>Injections of DAMGO (1-4 nmol in 0.5 µl) into the CeA significantly increased food intake in satiated rats, but did not affect water intake in rats with water deprivation. NTX (26.5 nmol in 0.5 µl) injected into the CeA antagonized DAMGO-induced feeding but D-AP-5 (6.3-25.4 nmol in 0.5 µl) injections did not produce such an effect.</p><p><b>CONCLUSION</b>µ-ORs in the CeA regulate food intake rather than water intake in rats, and the orexigenic role of µ-ORs is not dependent on the activation of the NMDA receptors in the CeA.</p>

Difference of the Naltrexone's Effects in Social Drinkers by Spicy Food Preference

The purpose of this study was to investigate the differences in subjective acute effects of alcohol and naltrexone among those who prefer spicy food to varying degrees. Acute biphasic alcohol effects scale (BAES), visual analogue scale for craving (VAS-C), blood alcohol concentration (BAC) and food preference scale were measured in 26 men. Repeated measures ANOVA (2 preference groupsx4 time blocks) on the stimulative subscale of BAES revealed a significant group by block interaction in naltrexone condition (N+) (P<0.001), but not in non-naltrexone condition (N-). Furthermore, repeated measures ANOVA (2 drug groupsx4 time blocks) on the stimulative subscale of BAES revealed a significant group by block interaction in strong preference for spicy food (SP) (P<0.001), but not in lesser preference for spicy food (LP). The paired t-test revealed that significant suppression of the stimulative subscale of BAES was observed at 15 min (P<0.001) and 30 min (P<0.001) after drinking when N+ compared with N- in SP. For those who prefer spicy food, the stimulative effect of acute alcohol administration was suppressed by naltrexone. This result suggests that the effect of naltrexone may vary according to spicy food preference.

Effects of Co-Administration of Intrathecal Nociceptin/Orphanin FQ and Opioid Antagonists on Formalin-Induced Pain in Rats

PURPOSE: Nociceptin/orphanin FQ (N/OFQ) as an endogeneous hexadecapeptide is known to exert antinociceptive effects spinally. The aims of this study were to demonstrate the antinociceptive effects of i.t. N/OFQ and to investigate the possible interaction between N/OFQ and endogenous opioid systems using selective opioid receptor antagonists in rat formalin tests. MATERIALS AND METHODS: I.t. N/OFQ was injected in different doses (1-10 nmol) via a lumbar catheter prior to a 50 microL injection of 5% formalin into the right hindpaw of rats. Flinching responses were measured from 0-10 min (phase I, an initial acute state) and 11-60 min (phase II, a prolonged tonic state). To observe which opioid receptors are involved in the anti-nociceptive effect of i.t. N/OFQ in the rat-formalin tests, naltrindole (5-20 nmol), beta-funaltrexamine (1-10 nmol), and norbinaltorphimine (10 nmol), selective delta-, micro- and kappa-opioid receptor antagonists, respectively, were administered intrathecally 5 min after i.t. N/OFQ. RESULTS: I.t. N/OFQ attenuated the formalin-induced flinching responses in a dose-dependent manner in both phases I and II. I.t. administration of naltrindole and beta-funaltrexamine dose-dependently reversed the N/OFQ-induced attenuation of flinching responses in both phases; however, norbinaltorphimine did not. CONCLUSION: I.t. N/OFQ exerted an antinociceptive effect in both phases of the rat-formalin test through the nociceptin opioid peptide receptor. In addition, the results suggested that delta- and micro-opioid receptors, but not kappa-opioid receptors, are involved in the antinociceptive effects of N/OFQ in the spinal cord of rats.

Functional activity of the cannabinoid 1 receptor is not affected by opioid antagonists in the rat brain / 대한마취과학회지

BACKGROUND: WIN55212-2 is a synthetic cannabinoid agonist and selective to cannabinoid 1 (CB1) receptors, which are distributed mainly in the central nervous system. Opioid receptors and CB1 receptors have several similarities in terms of their intracellular signal transduction mechanisms, distributions, and pharmacological action. Several studies have therefore sought to describe the functional interactions between opioids and cannabinoids at the cellular and behavioral levels. The present study investigated agonist-stimulated [35S]GTPgammaS binding by WIN55212-2 in rat brain membranes and determined the antagonism by selective opioid antagonists at the level of receptor-ligand interaction and intracellular signal transduction. METHODS: Sprague-Dawley rats (male, n = 20) were euthanized for the preparation of brain membranes. In agonist-stimulated [35S]GTPgammaS binding by WIN55212-2, the values of EC50 and maximum stimulation (% over basal) were determined in the absence or presence of the micro, kappa and delta opioid receptor antagonists naloxone (20 nM), norbinaltorphimine (3 nM), and naltrindole (3 nM), respectively. Ke values for opioid antagonist inhibition in the absence or presence of each opioid receptor antagonist were calculated using the following equation: [nanomolar antagonist] / (dose ratio of EC50 - 1). RESULTS: In WIN55212-2-stimulated [35S]GTPgammaS binding in the rat brain membranes, the values of EC50 and maximum stimulation (% over basal) were 154 +/- 39.5 nM and 27.6 +/- 5.3% over basal, respectively. Addition of selective opioid antagonists did not produce a significant rightward shift in the WIN55212-2 concentration-response curve, and Ke values were not applicable. CONCLUSIONS: Our results suggest that the functional activity of WIN55212-2-stimulated [35S]GTPgammaS binding was not affected by opioid antagonists in the rat brain membranes. Although the exact mechanism remains unclear, our results may partially elucidate their actions.

Do opioid receptors play a role in the pathogenesis of the inflammatory response in acute pancreatitis? / Os receptores opioides desempenham papel na patogênese da resposta inflamatória na pancreatite aguda?

PURPOSE: To investigate the effect of the opioid blocker naltrexone in the inflammatory response in acute pancreatitis (AP). METHODS: Acute pancreatitis was induced in anesthetized male Wistar rats by retrograde injection of 2.5% sodium taurocholate diluted in 0.5ml saline into the main pancreatic duct. Animals were randomized to the following experimental groups: Control Group (n=9): animals received an intraperitoneal injection of saline solution (0.5ml), 15 minutes before the induction of AP. Naltrexone Group (n=9): animals received an intraperitoneal injection of naltrexone 0.5ml (15 mg/kg), 15 minutes before induction of AP. Peritoneal levels of TNF-α and serum levels of IL-6 and amylase were determined The volume of the ascitic fluid was also evaluated. Myeloperoxidase (MPO) activities were analyzed in homogenates of pulmonary tissue. RESULTS: There were no significant differences in the ascitic fluid volume, nor in TNF-a and IL-6 levels in the naltrexone group compared to controls. Treatment with naltrexone did not affect the lung MPO activity compared to control group. CONCLUSIONS: The opioid receptors don't play an important role in the pathogenesis of the inflammatory response in acute pancreatitis. If opioids affect leukocytes inflammatory signaling, there are no major implications in the pathogenesis of acute pancreatitis.

OBJETIVO: Investigar o efeito do bloqueador opióide naltrexone na resposta inflamatória da pancreatite aguda. METODOS: Pancreatite aguda foi induzida em ratos machos Wistar, através de injeção retrógada de solução de taurocolato de sódio a 2,5% nos ductos pancreáticos. Os animais foram alocados em dois grupos: Grupo controle (n=9) animais receberam 0,5 ml de solução salina intra-peritonial 15 minutos antes da indução da pancreatite aguda e Grupo naltrexone (n=9) animais receberam naltrexone (15mg/kg de peso), em 0,5 ml de volume final por via intraperitoneal, 15 minutos antes da indução da pancreatite aguda. Foram avaliados o volume de ascite, os níveis séricos de amilase e IL-6, assim como TNF-α peritoneal e a atividade da mieloperoxidase (MPO) no tecido pulmonar. RESULTADOS: Não foram encontradas diferenças significantes nos parâmetros analisados entre o grupo que recebeu solução salina e o que recebeu naltrexone . CONCLUSÕES: Os receptores opióides não desempenham papel importante na resposta inflamatória sistêmica associada à pancreatite aguda. Se os opioides alteram a sinalização inflamatória nos leucócitos está ação não se reflete na patogênese da pancreatite aguda.

Receptores opioides até o contexto atual / Opioid receptors to date

JUSTIFICATIVA E OBJETIVOS: Devido à finalidade do ambulatório e os fármacos utilizados rotineiramente, o objetivo deste estudo foi rever e atualizar os conhecimentos sobre os receptores opioides e como complemento de estudo após palestra apresentada aos integrantes da equipe. CONTEÚDO: Foram revisados desde os aspectos históricos até os conhecimentos mais recentes sobre receptores opioides, descritos seus subtipos e mecanismos de ação. Para tal, foram consultadas referências indexadas pelo Pubmed. CONCLUSÃO: Com os dados presentes na literatura atual, concluiu-se que ainda existe muito a ser pesquisado sobre o tópico, visando medicações mais seguras e novas técnicas biomoleculares ainda são necessárias.

BACKGROUND AND OBJECTIVES: Due to the objective of the outpatient setting and to routinely used drugs, this study aimed at reviewing and updating the knowledge about opioid receptors and worked as a study complement after a lecture presented to team members. CONTENTS: We have reviewed from historical aspects to most recent developments about opioid receptors, in addition to describing subtypes and action mechanisms. For such, Pubmed-indexed references were queried. CONCLUSION: After reviewing current literature data, we have concluded that there is still a lot to be researched about the topic, aiming at safer drugs, and new biomolecular techniques are still needed.

Vértigo con nistagmo vertical por administración de morfina intratecal y reversión con naloxona / Vertigo and vertical nystagmus associated with intrathecal morphine administration and resolution by naloxone

La anestesia regional combinada es utilizada frecuentemente como herramienta para el tratamiento del dolor postoperatorio. Los efectos secundarios de los opioides utilizados por esta vía son similares a los que se presentan luego de la administración sistémica. La aparición de vértigo con nistagmo vertical es un efecto adverso muy pocas veces descripto con el uso de morfina por vía intratecal, epidural o endovenosa. Comunicamos el caso de un paciente que presentó esta complicación en el postoperatorio de una nefrectomía parcial, luego de la administración de morfina intratecal, con resolución completa mediante el uso de naloxona endovenosa.

Combined regional anesthesia is frequently used as a tool for management of postoperative pain. The profile of side effects of the opioids used via this route is similar to those occurring after systemic administration. The onset of vertigo with vertical nystagmus is an adverse effect rarely described after the use of intrathecal, epidural or intravenous morphine. We report the case of a patient who presented this complication in the postoperative period of a partial nephrectomy, after the administration of intrathecal morphine, with complete resolution by intravenous naloxone.

Involvement of opioid, adenosine and 5-HT3 receptors in antinociceptive effects of an ayurvedic polyherbal formulation

The present study was undertaken to evaluate the antinociceptive effects of an ayurvedic polyherbal formulation in rats and mice employing the tail immersion test and acetic acid-induced writhing test, respectively. With the tail immersion method, rats received two different doses [270 and 405 mg/kg BW, p.o.] of a formulation, pethidine [5.4 mg/kg BW, p.o.] as a reference standard and the combination of the higher dose of the formulation with naloxone [2 mg/kg, i.p.], an opioid receptor antagonist, and caffeine [16 mg/kg, i.p.], used as an adenosine receptor antagonist. In the acetic acid-induced writhing test, mice received two different doses [390 and 585 mg/kg, BW, p.o.] of formulation, diclofenac sodium [15 mg/kg, BW, p.o.] as a reference standard and the combination of the higher dose of the polyherbal formulation with ondansetron [0.5 mg/kg, i.p.], a serotonin receptor antagonist. The polyherbal formulation [405 mg/kg] exhibited a significant [p < 0.01] antinociceptive effect using the tail immersion method. In the acetic acid-induced writhing test, the formulation showed significant [p < 0.01] dose-dependent activity. The antinociceptive effect of the polyherbal formulation apparently involved an opiate-like mechanism, since its antinociceptive action was attenuated by naloxone pretreatment. In addition, antinociceptive activity was attenuated by caffeine and reversed by ondansetron pretreatment. Our data suggest that the polyherbal formulation possessed centrally and peripherally mediated antinociceptive properties. The activity could be mediated through opioid, adenosine, and serotonin receptors and via inhibition of cyclo-oxygenase- and/or lipoxygenase-dependent pathways

Morphine Postconditioning Attenuates ICAM-1 Expression on Endothelial Cells

The purpose of this study is to determine 1) whether morphine postconditiong (MPostC) can attenuate the intercellular adhesion molecules-1 (ICAM-1) expression after reoxygenation injury and 2) the subtype(s) of the opioid receptors (ORs) that are involved with MPostC. Human umbilical vein endothelial cells (HUVECs) were subjected to 6 hr anoxia followed by 12 hr reoxygenation. Three morphine concentrations (0.3, 3, 30 microM) were used to evaluate the protective effect of MPostC. We also investigated blockading the OR subtypes' effects on MPostC by using three antagonists (a micro-OR antagonist naloxone, a kappa-OR antagonist nor-binaltorphimine, and a delta-OR antagonist naltrindole) and the inhibitor of protein kinase C (PKC) chelerythrine. As results, the ICAM-1 expression was significantly reduced in the MPostC (3, 30 microM) groups compared to the control group at 1, 6, 9, and 12 hours reoxygenation time. As a consequence, neutrophil adhesion was also decreased after MPostC. These effects were abolished by coadministering chelerythrine, nor-binaltorphimine or naltrindole, but not with naloxone. In conclusion, it is assumed that MPostC could attenuate the expression of ICAM-1 on endothelial cells during reoxygenation via the kappa and delta-OR (opioid receptor)-specific pathway, and this also involves a PKC-dependent pathway.