Ozgur Yesilyurt

Effects of agmatine on ethanol withdrawal syndrome in rats

Effects of agmatine, which is an endogenous polyamine metabolite formed by decarboxylation of L-arginine, have been investigated on the ethanol withdrawal syndrome in rats. Adult male Wistar rats were used in the study. Ethanol (7.2% v/v) was given to the rats by a liquid diet for 21 days. Agmatine (20, 40, 80 and 160 mg/kg) and saline were injected to rats intraperitoneally 30 min before ethanol withdrawal testing. After 30th min, 2nd and 6th h of ethanol withdrawal, rats were observed for 5 min, and withdrawal signs which included locomotor hyperactivity, agitation, stereotyped behavior, wet dog shakes and tremor were recorded or rated. A second series of injections was given at 6 h after the first one, and subjects were then tested for audiogenic seizures. Agmatine caused dose-dependent and significant inhibitory effects on stereotyped behaviors, wet dog shakes and tremors during the observation period. It did not cause any significant change in motor coordination of naive (not ethanol-dependent) rats. Our results suggest that agmatine attenuates withdrawal syndrome in ethanol-dependent rats; thus, this drug may be beneficial in the treatment of ethanol dependence.

Topical cannabinoid enhances topical morphine antinociception

Opioids and cannabinoids produce antinociception through both spinal and supraspinal action. Both opioids and cannabinoids also have important peripheral action. Many previous studies indicate that systemically administered cannabinoids enhance antinociceptive properties of opioids. Experiments were conducted to test the hypothesis that topical cannabinoids would enhance the topical antinociceptive effects of morphine. Antinociception was measured in the radiant tail‐flick test after immersion of the tail of mice into a solution of dimethyl sulfoxide (DMSO) containing WIN 55, 212‐2, a cannabinoid agonist and morphine, an opioid agonist. Morphine and WIN 55, 212‐2 produce time dependent topical analgesic effects limited to the portion of the tail exposed to drugs. WIN 55, 212‐2 had a potency lower than that of morphine. The topical antinociceptive effects of WIN 55, 212‐2 were blocked by systemic pretreatment of cannabinoid CB1 receptor selective antagonist, AM 251. This suggests that topical antinociceptive effects of WIN 55, 212‐2 involve CB1 receptors. Combination of topical WIN 55, 212‐2 with topical morphine yielded significantly greater analgesic effects than that of topical morphine alone. The ability of the CB1 receptor antagonist AM 251 to antagonize the enhancement of antinociception of morphine by WIN 55, 212‐2 indicates that WIN 55, 212‐2 acts through a CB1 receptor to enhance the potency of topical morphine. Additionally, spinally administered ineffective doses of WIN 55, 212‐2 potentiated the antinociceptive effects of topical morphine. These results demonstrate an antinociceptive interaction between topical opioids with topical, and spinal cannabinoids. These observations are significant in using of topical combination of cannabinoid and morphine in the management of pain.

Agmatine Potentiates the Analgesic Effect of Morphine by an α2-Adrenoceptor-Mediated Mechanism in Mice

The effects of agmatine, which is an endogenous polyamine metabolite formed by decarboxylation of L-arginine, and a combination of agmatine and morphine on tail-flick test have been investigated in mice. Adult male Swiss–Webster mice were used in the study. Agmatine (10, 20 and 40 mg/kg), clonidine (0.15 mg/kg), yohimbine (0.625 and 1.25 mg/kg), or saline were injected into mice intraperitoneally. Morphine (1 and 2 mg/kg) was given subcutaneously. Agmatine alone did not produce any significant change on radiant tail-flick latencies, but it potentiated significantly and dose-dependently morphine-induced (1 mg/kg) analgesia. The potentiating effect of agmatine (40 mg/kg) on morphine-induced analgesia was blocked completely by yohimbine (0.625 mg/kg), a selective α2-adrenoceptor antagonist, pretreatment. Clonidine (0.15 mg/kg), an α2-adrenergic receptor agonist, caused a significant increase of the tail-flick latencies of the mice. Yohimbine (0.625 mg/kg) also blocked clonidine-induced analgesia. In addition, yohimbine (0.625 mg/kg) was ineffective on the tail-flick test and did not produce any significant change on the morphine-induced analgesia. Our results indicate that cotreatment of agmatine with morphine produces antinociceptive enhancement via an α2-adrenergic receptor-mediated mechanism and agmatine–morphine combination may be an effective therapeutic strategy for medical treatment of pain.

The interaction between IL-1β and morphine: possible mechanism of the deficiency of morphine-induced analgesia in diabetic mice

&NA; It is known that diabetic mice are less sensitive to the analgesic effect of morphine. Some factor(s) derived from mononuclear cells, e.g. interleukin‐1&bgr; (IL‐1&bgr;), may be responsible for the diminished analgesic effect of morphine in diabetic mice. Therefore, we examined direct effects of IL‐1&bgr;, intracerebroventricularly (i.c.v.), on morphine‐induced analgesia, subcutaneously (s.c.), in diabetic and control mice by using the tail‐flick test. Morphine at doses of 1, 2 and 5 mg/kg (s.c.) produced dose‐dependent analgesia in diabetic and control mice but diabetic mice were less sensitive to the analgesic effect of morphine when compared to the controls. IL‐1&bgr; at a dose of 0.1 ng/mouse produced analgesia in control mice but not in diabetics, whereas IL‐1&bgr; at a dose of 10 ng/mouse produced a hyperalgesic effect both in diabetic and control mice. IL‐1&bgr; at a dose of 1 ng/mouse has neither an analgesic nor a hyperalgesic effect in control and diabetic mice. Administration of a neutral (neither analgesic nor hyperalgesic) dose of IL‐1&bgr;, 1 ng/mouse (i.c.v.), just prior to administration of morphine (s.c.) abolished the analgesic effect of morphine at doses of 1, 2 and 5 mg/kg in control mice and the analgesic effect of morphine became similar to that in diabetics. The diminished analgesic effect of morphine in diabetes was attenuated further with IL‐1&bgr; at a dose of 1 ng/mouse (i.c.v.). These results suggest that the decreased analgesic effect of morphine in diabetes may be related to IL‐1&bgr;.

The Additive Antinociceptive Interaction Between WIN 55,212-2, a Cannabinoid Agonist, and Ketorolac

Combinations of nonsteroidal antiinflammatory drugs (NSAIDs) and opioids are widespread in the management of pain, allowing better analgesia with reduced side effects. Cannabinoids are promising analgesic drugs that have pharmacological properties similar to those of opioids. However, the beneficial effects of cannabinoids for pain treatment are counterbalanced by their psychotomimetic side effects. We designed the present study to evaluate the antinociceptive interaction between cannabinoids and NSAIDs in mice, using the acetic acid-induced writhing test and tail-flick test. Interactions were analyzed using isobolographic analysis. WIN 55,212-2, a cannabinoid agonist, and the NSAID ketorolac, either alone or in combination, produced dose-dependent antinociception in the writhing test. Isobolographic analysis showed additive interactions between WIN 55,212-2 and ketorolac when they were coadministered systemically. Ketorolac is inactive in the radiant heat tail-flick test in which WIN 55,212-2 was active. Ketorolac did not influence WIN 55,212-2–induced antinociception in the tail-flick test. This study demonstrated an additive antinociceptive interaction between WIN 55,212-2 and ketorolac in an inflammatory visceral pain model. The combination of cannabinoids and NSAIDs may have utility in the pharmacotherapy of pain.

Analgesic effects of amlodipine and its interaction with morphine and ketorolac-induced analgesia

1. The antinociceptive effects of amlodipine, administered subcutaneously (s.c.), intracerebroventricularly (i.c.v.) and intrathecally (i.t.) were examined with the acetic acid writhing and tail-flick tests in mice. Amlodipine was also tested in combination with morphine and ketorolac. Isobolographic analyses were used to define the nature of functional interactions between amlodipine and morphine or ketorolac. 2. The s.c. (0.1, 1.25, 2.5, 5 and 10 mg/kg), i.c.v. (2.5, 5, 10 and 20 micrograms/mice) and i.t. (2.5, 5, 10 and 20 micrograms/mice) administration of amlodipine exhibited a dose-dependent antinociceptive effect in the writhing test but had no effect on the tail-flick latency. Isobolographic analyses revealed an additive interaction between amlodipine and morphine or ketorolac in the writhing test. 3. These results suggest that amlodipine induces antinociception and increases antinociceptive action of morphine and ketorolac, possibly through a decrease in cellular calcium availability.

Simultaneous determination of cyclosporine A, tacrolimus, sirolimus, and everolimus in whole-blood samples by LC-MS/MS.

Objectives. Cyclosporine A (CyA), tacrolimus (TRL), sirolimus (SIR), and everolimus (RAD) are immunosuppressive drugs frequently used in organ transplantation. Our aim was to confirm a robust sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of CyA, TRL, SIR, and RAD in whole-blood samples. Materials and Methods. We used an integrated online solid-phase extraction-LC-MS/MS system and atmospheric pressure ionization tandem mass spectrometry (API-MS/MS) in the multiple reaction monitoring (MRM) detection mode. CyA, TRL, SIR, and RAD were simultaneously analyzed in whole blood treated with precipitation reagent taken from transplant patients. Results. System performance parameters were suitable for using this method as a high-throughput technique in clinical practice. The high concentration of one analyte in the sample did not affect the concentration of other analytes. Total analytical time was 2.5 min, and retention times of all analytes were shorter than 2 minutes. Conclusion. This LC-MS/MS method can be preferable for therapeutic drug monitoring of these immunosuppressive drugs (CyA, TRL, SRL, and RAD) in whole blood. Sample preparation was too short and simple in this method, and it permits robust, rapid, sensitive, selective, and simultaneous determination of these drugs.

Long-term exposure to repetitive hyperbaric oxygen results in cumulative oxidative stress in rat lung tissue

Context: Despite its known benefits, hyperbaric oxygen (HBO) is also reported to enhance the production of reactive oxygen species and can cause oxidative stress in several tissues. Previous studies had shown that HBO-induced oxidative stress is directly proportional to both its exposure pressure and duration. Nevertheless, these studies were usually performed with single-session HBO exposure but its clinical use commonly depends on long-term exposure periods. Objective: To clarify the oxidative effect of long-term repetitive HBO in the lung tissue of rats. Materials and methods: Male Sprague-Dawley rats were divided into six study groups exposed to consecutive HBO sessions (2.8 atm/90 min) for 5, 10, 15, 20, 30, and 40 days. Animals were sacrificed 24 h after the last HBO session. An additional control group was set to obtain normal data. Lung malondialdehyde (MDA) and carbonylated protein (PCC) levels were determined as measures of oxidative stress along with the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase. Results: None of the measured parameters showed any changes among the groups exposed to 5–15 HBO sessions. However, MDA, PCC, and SOD were found to be significantly increased in the 20 to 40 session groups. Discussion and conclusion: These results indicate that repetitive treatment with HBO may cause oxidative stress in critical tissues including the lung. Although HBO-mediated free radicals are accepted to be responsible for the benefits of this therapeutic modality, especially in cases with prolonged exposure, possible injurious effects of supranormal values of bio-oxidative products need to be considered.