European Journal of Pharmacology (v.499, #3)
Editorial Board (IFC).
Pseudolarix acid B inhibits angiogenesis by antagonizing the vascular endothelial growth factor-mediated anti-apoptotic effect by Wen-fu Tan; Xiong-wen Zhang; Mei-hong Li; Jian-min Yue; Yi Chen; Li-ping Lin; Jian Ding (219-228).
Angiogenesis is controlled by a number of growth factors, including vascular endothelial growth factor (VEGF). In this study, pseudolarix acid B, isolated from the traditional Chinese medicinal plant Pseudolarix kaempferi and originally identified as an early pregnancy-terminating agent, was evaluated for its potential as an angiogenesis inhibitor, using in vitro and in vivo models. After exposure to pseudolarix acid B 0.625–5 μM for 72 h, the proliferation of human umbilical vein endothelial cells was significantly inhibited. Pseudolarix acid B 0.313–2.5 μM for 24 h potently blocked the VEGF-induced tube formation of human umbilical vein endothelial cells in a dose-dependent manner. Matrigel plug assays disclosed that pseudolarix acid B reduced angiogenesis induced by VEGF in vivo. In addition, pseudolarix acid B antagonized VEGF-mediated anti-apoptotic effects on serum-deprived human umbilical vein endothelial cells and increased apoptosis of endothelial cells induced by VEGF in Matrigel plug assays. Moreover, pseudolarix acid B significantly inhibited VEGF-induced tyrosine phosphorylation of kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/flk-1), in correlation with a marked decrease in the phosphorylation of Akt and extracellular signal-regulated kinases (ERK). These findings collectively suggest that pseudolarix acid B possesses anti-angiogenic activity. One of the main anti-angiogenesis mechanisms of pseudolarix acid B may involve antagonism of the VEGF-mediated anti-apoptosis effect via inhibition of KDR/flk-1, ERK1/2, and Akt phosphorylation in endothelial cells.
Keywords: Pseudolarix acid B; Angiogenesis; Umbilical vein endothelial cell; Apoptosis; VEGF; KDR; (Human);
Pharmacological evaluation of α and β human tachykinin NK2 receptor splice variants expressed in CHO cells by Francesca Bellucci; Stefania Meini; Rose-Marie Catalioto; Claudio Catalani; Sandro Giuliani; Laura Quartara; Alessandro Giolitti; Angela Faiella; Luigi Rotondaro; Maria Luz Candenas; Francisco M. Pinto; Carlo Alberto Maggi (229-238).
In the present study, we have investigated, by binding and functional experiments, the pharmacological profile of a new human tachykinin NK2 receptor splice variant named β isoform. Neurokinin A, nepadutant, SR48968 [(S)-N-methyl-N[4-(4-acetylamino-4-phenyl piperidino)-2-(3,4-dichlorophenyl) butyl]benzamide] and substance P have been tested for binding on the receptor expressed in whole CHO transfected cells. Only SR48968 binds, but with an affinity about sixfold lower in respect to the α isoform. Moreover, neurokinin A was unable to inhibit the [3H]SR48968 binding to the β isoform up to μM concentrations. In cells expressing the human tachykinin NK2 receptor β isoform, contrary to those expressing the α isoform, natural or selective tachykinin receptor agonists (1 μM) were unable to produce a significant activation of inositol phosphate (IP) production or increase of intracellular calcium concentration [Ca2+]i. The recently discovered tachykinins, endokinins C and D, did not activate IP production or [Ca2+]i increase in cells expressing the α or β isoform of the human tachykinin NK2 receptor. The present data indicate that the human tachykinin NK2 receptor β isoform is poorly or not expressed on the cell membrane surface and that it may possibly act as a regulator of tachykinin NK2 receptor function. We cannot exclude the possibility that this receptor could interact with other presently unknown ligands.
Keywords: Tachykinin receptor NK2 α and β isoform; RNA splicing; Tachykinin; CHO cell;
Glycogen synthase kinase-3 inhibitors prevent caspase-dependent apoptosis induced by ethanol in cultured rat cortical neurons by Tsuneo Takadera; Takao Ohyashiki (239-245).
The effect of ethanol on cell viability was examined in rat cultured cortical neurons. Ethanol induced apoptosis, which was characterized by cell shrinkage, nuclear condensation or fragmentation and internucleosomal DNA fragmentation. Ethanol-induced apoptosis was prevented by N-methyl-d-aspartate (NMDA), an agonist of the NMDA receptor, which is a subtype of ionotropic glutamate receptors. Incubation with glycogen synthase kinase-3 (GSK-3) inhibitors 3-(2,4-dichlorophenyl)-4-(1-methyl-1H-indol-3-yl)-1H-pyrrole-2,5-dione (SB216763) and alsteropaullone, but not a cyclin-dependent protein kinase 5 inhibitor roscovitine, completely protected the neurons from ethanol-induced apoptosis. Apoptosis was accompanied by the activation of caspase-3 and prevented by a caspase-3 inhibitor. These results suggest that ethanol induces caspase-dependent apoptosis mediated by glycogen synthase kinase-3 activation in cultured rat cortical neurons.
Keywords: Ethanol; Apoptosis; Glycogen synthase kinase-3; NMDA receptor; Ca2+; Caspase;
Spinal vs. supraspinal antinociceptive activity of the adenosine A1 receptor agonist cyclopentyl-adenosine in rats with inflammation by Guillermo Ramos-Zepeda; Wolfgang Schröder; Silke Rosenow; Juan F. Herrero (247-256).
The adenosine A1 receptor is involved in spinal cord antinociception. As its role at supraspinal sites is not well known, we studied the systemic effects of its agonist N-cyclopentyl-adenosine (CPA) in single motor units from adult-spinalized, intact and sham-spinalized rats. CPA was not effective after spinalization, but it was very effective in intact animals (ID50: 92±1.3 μg/kg, noxious pinch) and over 10-fold more potent in sham-spinalized animals (ID50 of 8.3±1 μg/kg). Wind-up was also inhibited by CPA. We also studied the effect of CPA in the immature spinal cord preparation, where CPA dose-dependently inhibited responses to low (IC50s: 9±0.7 and 7.7±1.3 nM) and high intensity stimulation (IC50s: 4.9±0.5 and 12.1±2 nM). We conclude that the integrity of the spinal cord is crucial for the antinociceptive activity of systemic CPA in adult rats but not in immature rats, not yet influenced by a completely developed supraspinal control.
Keywords: Pain; Wind-up; Single motor unit; Spinal cord; Adenosine; Inflammation;
A role for l-glutamate ionotropic receptors in the development of rat neurogenic pulmonary edema by Hiroko Kondo; Guo-Gang Feng; Kimitoshi Nishiwaki; Yasuhiro Shimada; Mitsuru Hirokawa; Toru Komatsu; Takashi Yokochi; Naohisa Ishikawa (257-263).
The present study was undertaken to evaluate possible roles of l-glutamate ionotropic receptors in neurogenic pulmonary edema. Perfusion of l-glutamate into the fourth ventricles of rats increased nitric oxide (NO) signals in the efflux solution concentration-dependently, significantly reducing both the occurrence and severity of neurogenic pulmonary edema. This effect was completely reversed by prior intracisternal injection of an NO synthase inhibitor, N ω-nitro-l-arginine methyl ester (l-NAME), or an N-methyl-d-aspartate (NMDA) receptor antagonist, dizocilpine maleate (MK-801), and partially by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a 2-amino-3-hydroxy-5-methyl-4-isoxazol propionic acid (AMPA)/kainic acid receptor antagonist. Administration of MK-801 or CNQX alone, without l-glutamate, almost completely prevented neurogenic pulmonary edema development. These results suggest that endogenous l-glutamate may facilitate underlining disease process, whereas l-glutamate exogenously applied into the fourth ventricle may have an inhibitory action via release of NO, through ionotropic receptors.
Keywords: Neurogenic pulmonary edema; Nitric oxide; l-glutamate; Ionotropic receptor; MK-801; CNQX;
Adenosine A1-receptor-mediated tonic inhibition of glutamate release at rat hippocampal CA3–CA1 synapses is primarily due to inhibition of N-type Ca2+ channels by Satoshi Manita; Yoshinobu Kawamura; Kazuki Sato; Masashi Inoue; Yoshihisa Kudo; Hiroyoshi Miyakawa (265-274).
The voltage-gated Ca2+ channels responsible for synaptic transmission at CA3–CA1 synapses are mainly P/Q- and N-types. It has been shown that tonic inhibition of transmission due to activation of adenosine A1 receptors occurs at this synapse. We have recently developed a technique to monitor synaptically released glutamate which is based on synaptically induced glial depolarisation. Using this technique, we have examined the effects of different voltage-gated Ca2+ channel blockers on glutamate release. Under conditions in which the adenosine A1 receptor was not blocked, ω-AgaIVA (a P/Q-type voltage-gated Ca2+ channel blocker) suppressed synaptically induced glial depolarisation to a greater extent than ω-CgTxGVIA (an N-type voltage-gated Ca2+ channel blocker) did. In contrast, in the presence of an adenosine A1 receptor antagonist, ω-AgaIVA was less effective at suppressing synaptically induced glial depolarisation than ω-CgTxGVIA. These results indicate that, in the absence of adenosine A1 receptor-mediated tonic inhibition, the contribution of N-type is much greater than that of P-type, and that N-types are the primary target of tonic inhibition in normal conditions in which adenosine A1 receptor-mediated tonic inhibition is present.
Keywords: Presynaptic terminal; Ca2+ channel; Adenosine receptor; Hippocampus;
Amitriptyline produces multiple influences on the peripheral enhancement of nociception by P2X receptors by James B. Waldron; Allison R. Reid; Jana Sawynok (275-283).
Peripherally administered amitriptyline exhibits potential to be a locally active analgesic, while ATP augments peripheral nociception by interacting with P2X3 receptors on sensory afferents. The present study examined the effects of amitriptyline on flinching and biting/licking behaviours and thermal hyperalgesia produced by αβ-methylene-ATP (αβ-MeATP), a ligand for P2X3 receptors, following intraplantar administration into the hindpaw of rats. Coadministration of low doses of amitriptyline (up to 100 nmol) with αβ-MeATP augmented thermal hyperalgesia and flinching behaviours. The most active dose of amitriptyline (100 nmol) had no intrinsic effect. Augmentation of αβ-MeATP actions appears to be due to increased tissue levels of biogenic amines resulting from inhibition of uptake, as phentolamine (α1/α2-adrenergic receptor antagonist) and methysergide (5-hydroxytryptamine or 5-HT1/5-HT2 receptor antagonist) inhibit the augmented flinching produced by αβ-MeATP/amitriptyline. When noradrenaline and 5-HT were coadministered with αβ-MeATP (both increase the effect of αβ-MeATP), amitriptyline had no effect on flinching produced by αβ-MeATP/noradrenaline but inhibited flinching produced by αβ-MeATP/5-HT. In the presence of low concentrations of formalin (0.5%, 1%; which also increase the effect αβ-MeATP), amitriptyline inhibited augmented behaviours. Higher doses of amitriptyline (300–1000 nmol) increased thermal thresholds, suppressed thermal hyperalgesia produced by αβ-MeATP, and inhibited flinching produced by αβ-MeATP. Collectively, these results indicate that amitriptyline produces complex influences on peripheral pain signaling by P2X receptors. Lower doses augment nociception by αβ-MeATP (probably by inhibiting noradrenaline and 5-HT uptake) but inhibit αβ-MeATP responses in the presence of inflammatory mediators (perhaps reflecting receptor blocking properties); higher doses uniformly inhibit nociception by αβ-MeATP (perhaps reflecting local anesthetic properties).
Keywords: Amitriptylin; Nociception; P2X receptor;
The influence of gastric pentadecapeptide BPC 157 on acute and chronic ethanol administration in mice by Alenka Boban Blagaic; Vladimir Blagaic; Zeljko Romic; Predrag Sikiric (285-290).
The stable gastric pentadecapeptide BPC 157 (GEPPPGKPADDAGLV, M.W.1419), which was promising in inflammatory bowel disease (PL-10, PLD-116, PL-14736, Pliva) trials, protects against both acute and chronic alcohol-induced lesions in stomach and liver, but also, given peripherally, affects various centrally mediated disturbances. Now, in male NMRI mice BPC 157 (10 pg intraperitoneally, 10 ng and 10 μg, intraperitoneally or intragastrically) (i) strongly opposed acute alcohol (4 g/kg intraperitoneally) intoxication (i.e., quickly produced and sustained anesthesia, hypothermia, increased ethanol blood values, 25% fatality, 90-min assessment period) given before or after ethanol, and (ii) when given after abrupt cessation of ethanol (at 0 or 3 or 7 h withdrawal time), attenuated withdrawal (assessed through 24 hours) after 20%-alcohol drinking (7.6 g/kg) through 13 days, with provocation on the 14th day.
Keywords: Stable gastric pentadecapeptide BPC 157; Acute alcohol intoxication; Withdrawal/chronic alcohol consumption;
Enhancement of anxiety-like responsiveness to the cannabinoid CB1 receptor agonist HU-210 following chronic stress by Matthew N. Hill; Boris B. Gorzalka (291-295).
The effect that chronic unpredictable stress had on the anxiety-like response elicited by the cannabinoid receptor agonist HU-210 [3-(1,1-dimethylheptyl)-(-)-11-hydroxy-delta8-tetrahydrocannabinol] in the elevated plus maze was investigated here. Male Long–Evans rats were either unstressed or were subjected to a 21-day regimen of chronic unpredictable stress, and subsequently were subdivided into three testing groups (vehicle, 10 and 50 μg/kg of HU-210) and tested on the elevated plus maze. Results demonstrated that in unstressed animals, a low dose of HU-210 induced an anxiolytic response, whereas a high dose induced an anxiogenic response. Further, in stressed animals both the low and the high doses of HU-210 induced anxiogenic responses. These findings suggest that chronic stress enhances either cannabinoid receptor responsivity or one of the interacting systems implicated in emotional states.
Keywords: Cannabinoid; Anxiety; Elevated plus maze; Chronic stress; (Rat);
Vascular effects of the Mangifera indica L. extract (Vimang) by Amada E. Beltrán; Yolanda Alvarez; Fabiano E. Xavier; Raquel Hernanz; Janet Rodriguez; Alberto J. Núñez; María J. Alonso; Mercedes Salaices (297-305).
The effects of the Mangiferia indica L. (Vimang) extract, and mangiferin (a C-glucosylxanthone of Vimang) on the inducible isoforms of cyclooxygenase (cyclooxygenase-2) and nitric oxide synthase (iNOS) expression and on vasoconstrictor responses were investigated in vascular smooth muscle cells and mesenteric resistance arteries, respectively, from Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Vimang (0.5–0.1 mg/ml) and mangiferin (0.025 mg/ml) inhibited the interleukin-1β (1 ng/ml)-induced iNOS expression more in SHR than in WKY, and cyclooxygenase-2 expression more in WKY than in SHR. Vimang (0.25–1 mg/ml) reduced noradrenaline (0.1–30 μM)- and U46619 (1 nM–30 μM)- but not KCl (15–70 mM)-induced contractions. Mangiferin (0.05 mg/ml) did not affect noradrenaline-induced contraction. In conclusion, the antiinflammatory action of Vimang would be related with the inhibition of iNOS and cyclooxygenase-2 expression, but not with its effect on vasoconstrictor responses. Alterations in the regulation of both enzymes in hypertension would explain the differences observed in the Vimang effect.
Keywords: Vimang; Mangiferin; iNOS; Cyclooxygenase-2; Vascular smooth muscle cell; Mesenteric resistance artery;
Resistance of cholestatic rats against epinephrine-induced arrhythmia: the role of nitric oxide and endogenous opioids by Amir Reza Hajrasouliha; Sina Tavakoli; Pejman Jabehdar-Maralani; Hamed Shafaroodi; Amir Ali Borhani; Golbahar Houshmand; Hamed Sadeghipour; Mehdi Dehghani; Ahmad Reza Dehpour (307-313).
Short-term ligation of bile duct has been used as a model to study acute cholestasis and is associated with various cardiovascular abnormalities. We examined the role of nitric oxide (NO) and endogenous opioids on epinephrine-induced arrhythmia in 7-day bile duct-ligated (BDL) rats. Six groups of rats, each of which was subdivided into two subgroups (sham-operated and BDL), were examined. First group of animals were chronically treated with normal saline. In the second and third groups, single intraperitoneal administration of N(ω)-nitro-l-arginine methyl ester (l-NAME, 10 mg/kg) or naltrexone (20 mg/kg) was performed 30 min before evaluation of epinephrine-induced arrhythmia. Two groups received chronic administration of low dose (3 mg/kg/day) or high dose (10 mg/kg/day) l-NAME; and the last group was treated chronically with naltrexone (20 mg/kg/day). Chronic drug administration was performed subcutaneously for 6 consecutive days following BDL or sham operation. After induction of arrhythmia by intravenous injection of 10 μg/kg epinephrine, mean arterial pressure and electrocardiogram were recorded for 1 min. Heart rate and mean arterial pressure were significantly lower in BDL rats (P<0.01). Chronic injection of naltrexone increased heart rate and mean arterial pressure in BDL (P<0.05). Chronic low dose l-NAME administration had no effect on baseline hemodynamic parameters. High dose l-NAME injection corrected hypotension in BDL rats, but not bradycardia (P<0.05). Epinephrine induced less arrhythmia in BDL rats (P<0.05). Acute and chronic injection of naltrexone had no effect on the resistance of BDL rats against epinephrine-induced arrhythmia. Although acute l-NAME administration enhanced arrhythmias in sham-operated rats (P<0.001), it had no effect on BDL animals. Chronic injection of low dose or high dose l-NAME, without having any effect on sham-operated animals, increased arrhythmias in BDL rats (P<0.01). This study showed that BDL animals are resistant against epinephrine-induced arrhythmia and this resistance depends on long-term NO overproduction.
Keywords: Cholestasis; NO (Nitric oxide); Endogenous opioids; Epinephrine-induced arrhythmia; (Rat);
Magnitude and time course of platelet inhibition with Aggrenox® and Aspirin in patients after ischemic stroke: the AGgrenox versus Aspirin Therapy Evaluation (AGATE) trial by Victor L. Serebruany; Alex I. Malinin; David C. Sane; Bernd Jilma; Aviv Takserman; Dan Atar; Charles H. Hennekens (315-324).
The European Stroke Prevention Study showed greater stroke prevention for Aggrenox® than either for aspirin or dipyridamole alone. To test whether Aggrenox® has superior antiplatelet properties to aspirin alone we conducted the AGgrenox versus Aspirin Therapy Evaluation (AGATE) trial. Forty patients with prior ischemic stroke not taking aspirin for at least 30 days were randomized to Aggrenox® (2 pills/daily) or aspirin (81 mg plus matching placebo/daily) for 30 days. Platelet function was assessed at baseline, 24 h, and days 3, 7, 15, and 30 by aggregometry, flow cytometry and cartridge-based analyzers. Both Aggrenox® and aspirin provided fast and sustained platelet inhibition. Aggrenox®, however, especially after 15 days, showed significant prolongation of the closure time (P=0.04), diminished expression of platelet/endothelial cell adhesion molecule-1 (PECAM-1) (P=0.01), glycoprotein IIb (GPIIb) antigen (P=0.02), and GPIIb/IIIa activity (P=0.01) by PAC-1 C antibody, CD63 (P=0.03), as well as inhibition of Protease Activated Receptors (PAR-1) associated with intact (SPAN12, P=0.01) and cleaved (WEDE15, P=0.01) thrombin receptors as compared with aspirin. Surprisingly, GPIb expression increased, especially after aspirin. In the randomized trial of small sample size, aspirin and Aggrenox® produced fast and sustained platelet inhibition. In 25 of 90 direct comparisons, Aggrenox® was superior to aspirin, whereas in 4 of 90, aspirin was superior to Aggrenox®. In 61 of 90 direct comparisons, aspirin and Aggrenox® were equivalent. Aggrenox® was associated with a profound reduction of PAR-1 receptors, an observation that may be related to the greater clinical benefit of Aggrenox® compared with Aspirin in preventing recurrent stroke.
Keywords: Randomized trial; Aspirin; Aggrenox®; Platelet; Stroke;
Deletion of inducible nitric oxide synthase decreases mesenteric vascular responsiveness in portal hypertensive mice by Sotiria Bexis; Catherine Vandeputte; P. Aiden McCormick; James R. Docherty (325-333).
The effects of pre-hepatic portal hypertension were examined on the responsiveness of aorta and mesenteric artery from wild-type, inducible nitric oxide synthase knockout (iNOS-KO) and endothelial nitric oxide synthase knockout (eNOS-KO) mice. Mice were sham-operated or made portal hypertensive by creating a calibrated portal vein stenosis. Acetylcholine produced marked relaxations in phenylephrine (10 μM) contracted aorta and mesenteric artery from wild-type and iNOS-KO, both sham and portal hypertensive, but relaxations were abolished in vessels from eNOS-KO mice. There were no significant differences between sham and portal hypertensive animals within groups in the effects of acetylcholine. The potency of KCl was significantly increased in aorta and mesenteric artery from eNOS-KO mice. The maximum contraction to the α1-adrenoceptor agonist phenylephrine was significantly increased in aorta from eNOS-KO, as compared with wild-type mice. There were no significant differences between sham and portal hypertensive animals within each group in contractions of aorta to KCl or phenylephrine. However, in mesenteric artery, although portal hypertension did not change responsiveness in wild-type or eNOS-KO as compared to sham animals, the potency of phenylephrine was significantly reduced in portal hypertensive iNOS-KO mice as compared to shams. Hence, portal hypertension as compared to sham operation did not affect responses to vasoconstrictors in mouse aorta, but in mouse mesenteric artery portal hypertension affected vascular responses in iNOS-KO mice, suggesting that iNOS is involved in the mesenteric vascular response to portal vein ligation.
Keywords: Nitric oxide; iNOS; iNOS knockout; eNOS knockout; NOS-2 knockout; NOS-3 knockout; l-NAME; Portal hypertension; mesenteric artery, mouse;
Adenosine 5′-triphosphate and noradrenaline are excitatory cotransmitters to the fibromuscular stroma of the guinea pig prostate gland by Rosanda Buljubasich; Sabatino Ventura (335-344).
Immunohistochemical studies demonstrated abundant P2X1-receptor immunoreactivity colocalized with α-actin within the fibromuscular stroma of the guinea pig prostate. P2X2-, P2X3- and P2X4-receptor immunoreactivity was absent. αβmethylene Adenosine 5′-triphosphate (ATP) attenuated contractile responses to electrical field stimulation (50 V, 0.5 ms, 5–20 Hz) in the absence and presence of prazosin (0.3 μM). Responses to 1–2 Hz were unaffected. ARL 67156 (6-N, N-Diethyl-β-γ-dibromomethylene-d-adenosine-5-triphosphate; 100 μM) enhanced contractile responses to electrical field stimulation (50 V, 0.5 ms, 10–20 Hz). Concentration–response curves to exogenously applied ATP analogues on unstimulated preparations elicited concentration-dependent suramin (100 μM)-sensitive contractions. The rank order of potency was: αβmethylene ATP>2methylthio ATP=βγmethylene ATP>adenosine 5′-diphosphate (ADP)=ATP. Adenosine and adenosine 5′-monophosphate (AMP) did not produce contractile responses. These results demonstrate the presence of functional P2X1-receptors within the fibromuscular stroma of the guinea pig prostate and suggest a cotransmitter role for ATP with noradrenaline during high-frequency stimulation.
Keywords: Adenosine 5′-triphosphate; Fibromuscular stroma; Neuromuscular cotransmission; Prostate; P2X-receptor; Smooth muscle;
Melatonin treatment protects against diabetes-induced functional and biochemical changes in rat aorta and corpus cavernosum by Kübra Paskaloglu; Göksel Șener; Gül Ayanğolu-Dülger (345-354).
Enhanced oxidative stress due to diabetes is accepted to lead to endothelial dysfunction, and this is known to play a key role in the pathogenesis of diabetic vascular diseases and complications. This study was designed to determine the possible protective effect of melatonin and/or insulin treatment on the functional and biochemical changes caused by hyperglycemia in aorta and corpus cavernosum of diabetic rats. Wistar albino male rats were rendered diabetic by injecting streptozotocin (60 mg/kg, intraperitoneally (i.p.)). Melatonin (10 mg/kg, i.p.) and/or insulin (6 U/kg, subcutaneously (s.c.)) were administered for 8 weeks. In the diabetic group, the contractile responses of aortic strips to phenylephrine were significantly impaired (EC50 5.5×10−7 M in diabetic and EC50 1.47×10−7 M in the control group, P<0.001). Treatment with melatonin (EC50 4.6×10−7 M) or insulin+melatonin (EC50 1.68×10−7 M, P<0.001) improved the contractile responses. Acetylcholine caused a dose-dependent relaxation response (EC50 1.58×10−7 M) which was impaired in the diabetic group (EC50 26×10−7 M, P<0.001). There was less impairment in melatonin-, insulin- and insulin+melatonin-treated groups (EC50 11.61×10−7, 7.3×10−7 and 1.41×10−7 M, respectively, P<0.01). Contractile responses to phenylephrine were also impaired in the corpus cavernosum strips (EC50 2.06×10−5 M in diabetic and 0.94×10−5 M in the control group, P<0.001). In the melatonin- (EC50 1.59×10−5 M) and insulin+melatonin-treated (EC50 1.53×10−5 M, P<0.5) groups contractile responses were improved. In the diabetic group, the relaxation responses of corpus cavernosum strips to acetylcholine were impaired (EC50 24.12×10−5 M, P<0.001), and treatment with melatonin (EC50 0.68×10−5 M), insulin (EC50 0.53×10−5 M) or insulin+melatonin (0.98×10−5 M, P<0.001) restored the responses to acetylcholine. In diabetic tissues, malondialdehyde levels were increased while glutathione levels were decreased, demonstrating oxidative damage. This was also prevented by treatment with melatonin or the melatonin and insulin combination. The diabetic state enhances the generation of free radicals, and both melatonin and insulin treatments reduced this oxidative stress; however, treatment with the combination was the most efficient in preventing diabetes-induced damage. Thus, our results suggested that giving diabetic patients adjuvant therapy with melatonin may have some benefit in controlling diabetic complications.
Keywords: Streptozotocin; Aorta; Corpus cavernosum; Melatonin; Insulin;
The NK1 receptor antagonist WIN51708 reduces sensitization after chronic cocaine by Colin Davidson; Tong H. Lee; Everett H. Ellinwood (355-356).
We tested the tachykinin NK1 receptor antagonist WIN51708 (17βhydroxy17αethynyl5αandrostanol[3,2b]pyrimido[1,2-a]benzimidazole) in a behavioral sensitization model. Rats were given 7 days of cocaine then 7 days of withdrawal to induce sensitization. Thereafter, another 7 days of cocaine with WIN51708 (2 mg/kg i.p.) given 3.5 h after each cocaine injection was given. WIN51708 reversed sensitization but had no effect on controls. NK1 receptor antagonists may have use in stimulant abuse and schizophrenia treatment.
Keywords: Cocaine; Sensitization; NK1;
Author index (357-359).
Keyword index (361-366).