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.

Avances en la comprensión de las adicciones: niveles, modelos, farmacoterapia / Progress in the understanding of addictins: Levels, models, pharmacotherapy

La comprensión de los mecanismos subyacentes en las diversas adicciones avanza continuamente. Las diferentes líneas de investigación, ya sea tanto en el plano molecular, o de los circuitos y áreas involucradas, como así también de los abordajes psicosociales, profundizan su búsqueda con el objetivo de mejorar la eficacia de los tratamientos. Un interesante artículo de Koob y colaboradores (2009), que lleva por subtítulo El abordaje de la piedra de Rosetta, revisa detalladamente los distintos niveles en juego en esta compleja problemática. El objetivo del mencionado artículo es aportar elementos en el sentido de favorecer el desarrollo de fármacos adecuados para el tratamiento de estas condiciones patológicas, que incluyen tanto el uso de drogas ilícitas, como del alcohol y el tabaco. Las actuales farmacoterapias utilizadas para el tratamiento de la adicción pueden ser empleadas para validar y mejorar los modelos de laboratorios en animales y humanos, para así identificar nuevos candidatos viables para tratamientos. Esta aproximación tiene la capacidad de promover la investigación traslacional y puede proveer un marco heurístico para desarrollar farmacoterapias eficientes y efectivas para la adicción

The comprehension of the mechanisms underlying the different addictions is in constant progess. The different lines of research, both in the molecular field or the circuits and areas involved, as well as in psychosocial approaches emphasize their investigations with the purpose of enhancing the efficacy of the treatments. An interesting article by Koob et al (2009), which is subtitled "The Rosetta Stone Approach", provides a detailed review of the different levels involved in this complex issue. The purpose of the mentioned article is to provide elements that promote the development of pharmacological drugs suitable for the treatment of these pathological conditions, which include both the use of illegal drugs, as well as acohol and tobacco. The current pharmacological therapies used for the treatment of addiction can be used to validate and improve labortory models in animals and humans, in order to identify new potential candidates for treatments. This approach is able to promote a translational research and can offer a heuristic framework to develop efficient and effective pharmacotherapies for addiction

Naltrexone influences protein kinase C epsilon and integrin alpha7 activity in SH-SY5Y neuroblastoma cells

Alcohol influences the neuroadaptation of brain cells where receptors and enzymes like protein kinase C (PKC) exist. Naltrexone acts on opioid receptors. However, other mechanisms of action remain unknown. We prepared SH-SY5Y neuroblastoma cells, and fed them with 150 mM ethanol for 72 h followed by treatment with naltrexone for 24 h. We performed microarray analysis and reverse transcriptase-polymerase chain reaction. Our results showed that PKC epsilon increased 1.90 times and showed an overall decreasing pattern as time increased. Phosphorylated ERK also increased 2.0 times according to the change of PKC epsilon. Integrin alpha7 increased 2.32 times and showed an increasing pattern as time increased. In conclusion, naltrexone influences PKC epsilon neuronal signaling system and endothelial adhesion molecule integrin alpha7 in addition to the well-known opioid system.

Stereological study of rat spleen following acute ethanol treatment.

To investigate the acute effect of ethanol (4 g/kg, i.p.) on spleen adult female Wistar rats were treated intraperitoneally with: a) ethanol (4 g/kg body wt), b) naltrexone (5 mg/kg body wt) followed 45 minutes later by ethanol (4 g/kg body wt) and c) naltrexone (5 mg/kg body wt) alone. Untreated and saline-treated rats were used as controls. Twenty hours after the ethanol treatment the animals were sacrificed and the spleens were removed. A piece of tissue from the central part of each organ was fixed in Bouin's solution. Paraffin sections were stained with hematoxylin-eosin and analysed using stereological measurements. The volume densities of the following tissue compartments: red pulp, white pulp (divided in follicles, periarterioral lymphatic sheath and marginal zone) and the connective tissue were determined. Stereological analysis also included parameters of follicles: the areal numerical density (the number of follicles per 1 mm2 of tissue section), the numerical density (the number of follicles per mm3 of tissue) and the mean follicle diameter. The immunoarchitecture of the spleen was preserved following acute ethanol treatment. Unlike other parameters that were unaffected, ethanol evoked a decrease in both volume density of follicle and the mean follicle diameter. Naltrexone pretreatment had no influence on ethanol-induced changes. The data obtained indicate that a single dose of ethanol has a profound effect on rat spleen affecting the follicles, but the mechanism of its action remains to be elucidated.

Effects of naltrexone and cross-tolerance to morphine in a learned helplessness paradigm

Opiates have been implicated in learned helplessness (LH), a phenomenon known to be related to opiate stress-induced analgesia (SIA). In the present study, we investigated the role of opiates in the induction of LH and SIA under different conditions. Adult female Wistar rats were trained either by receiving 60 inescapable 1-mA footshocks (IS group, N = 114) or by confinement in the shock box (control or NS group, N = 92). The pain threshold of some of the animals was immediately evaluated in a tail-flick test while the rest were used 24 h later in a shutttle box experiment to examine their escape performance. The opiate antagonist naltrexone (0 or 8 mg/kg, ip) and the previous induction of cross-tolerance to morphine by the chronic administration of morphine (0 or 10 mg/kg, sc, for 13 days) were used to identify opiate involvement. Analysis of variance revealed that only animals in the IS group demonstrated antinociception and an escape deficit, both of which were resistant to the procedures applied before the training session. However, the escape deficit could be reversed if the treatments were given before the test session. We conclude that, under our conditions, induction of the LH deficit in escape performance is not opiate-mediated although its expression is opiate-modulated.

Influence of chronic prenatal and postnatal administration of naltrexone in locomotor activity induce by morphine in mice

The influence of chronica pre- and postnatal naltrexone exposure on the sensitivity of off spring to the locomotor effects of morphine was investigated i C-57 Black mice. Pregnant mice were injected subcutaneously (sc) with either saline (0.1 ml/10 g) or naltrexone (10 mg/kg) twice daily during gestation and throughout lactation, 21 days postpartum. One, three and seven weeks after bith, male offspring were tested for locomotor activity. At 7 weeks of age, dose-response curves were obtained with morphine (10, 31.6, and 100 mg/kg) and amphetamine (0.31, 10 and 31.6 mg/kg) in naltrexone-pretreated and in saline-treated animals. Naltrexone exposure during gestation and lactation resulted in an augmented sensitivity of offspring to the locomotor activity increasing effects of morphine. In these animals, the dose-response relationship for the effect of morphine on locomotor activity was displaced to the left about threefold. In contrast, naltrexone exposure did not alter the sensitivity of offspring to amphetamine. It was also found that ofsspring of naltrexone-treated animals have significantly greater spontaneous locomotor activity than that of the offspring of saline treated mothers. The increased locomotor activity persisted for at least 4 weeks after the last injection of naltrexone. These findings indicate that chronic opioid receptor blockade during gestation and early portnatal development induces supersensitivity to the locomotor effects of morphine and is associated with long-lasting behavioral alterations

Role of kappa opioid receptors during stress responsiveness in rats.

Effects of kappa opioid agonist, ketocyclazocine (KCZ) and its antagonist, M(r) 2266, were evaluated on some stress responses in rats. KCZ (1 or 10 mg/kg, ip) dose-dependently attenuated cold restraint stress (CRS)-induced gastric ulcer formation. Similar gastric cytoprotection was also seen with KCZ (1 or 10 micrograms/rat, icv). Pretreatment of rats with M(r) 2266 (0.3 mg/kg, ip) clearly antagonized the ulceroprotective effects of both ip and icv KCZ. KCZ effects on the gastric mucosa during CRS were also reduced by naltrexone (5 mg/kg, ip) pretreatment. KCZ (1 or 10 mg/kg, ip) also attenuated the plasma corticosterone response to CRS and these effects were blocked by M(r) 2266 (0.3 mg/kg) pretreatment. These results indicate kappa opioid receptor involvement during stress reactions and also suggest possible opioidergic interactions during CRS.

Effects of stress on immune responsiveness, gastric ulcerogenesis and plasma corticosterone in rats: modulation by diazepam and naltrexone.

Effects of restraint stress (24 hr at room temperature) were evaluated on some immunological, visceral and endocrinal responses in rats. In animals sensitized with sheep RBC (SRBC), restraint stress (a) prevented the booster-induced rise in anti-SRBC antibody titre, (b) induced gastric mucosal erosions, and (c) elevated plasma corticosterone, when compared to non-stressed controls. Diazepam (1 or 10 mg/kg) consistently attenuated the effects of stress on all three parameters studied. The opioid antagonist, naltrexone (1 or 5 mg/kg) tended to aggravate these stress-induced effects. These concurrent biological changes during stress and their modulation by drugs are discussed in light of a possible correlation between endocrinal, immunological and visceral changes during such aversive stimuli.

Diazepam inhibits retroactive interference of memory in humans: pretreatment with naltrexone does not alter this effect

1. In a double-blind of the effects of diazepam and naltrexone on retroactive memory interference, 88 health human volunteers were asked to study a text on the 1954 world Soccer Cup and were submitted to a written questionnaire on the material 48 h later. Three hours reading the text, 58 of the subjects were exposed to a non-factual, derogatory comment on the worls Cup. 2. All subjects were given either placebo or naltrexone (50 mg) before reading the text, and either placebo or diazepam (5 mg), per os, 2h after reading the text (1 h prior to the comment), Subjects were assigned to the different treatment groups by a double-blind design. 3. Exposure to the derogatory comment caused retroactive memory interference with the retention of material from the text. Diazepam blocked the retroactive interference and had no effect of its own on retention of the text. Pretreatment with naltrexone did not influence retention, retrograde interference, or the effect of diazepam on these variables. 4. The results obtained here extend to health adult humans observations made on rats and mice in which diazepam blocked retroactive interference