European Journal of Pharmacology (v.434, #3)

Neuroprotective and neurotoxic effects of monoamine oxidase-B inhibitors and derived metabolites under ischemia in PC12 cells by Saleh Abu-Raya; Rinat Tabakman; Eran Blaugrund; Victoria Trembovler; Philip Lazarovici (109-116).
Selegiline and rasagiline are selective and irreversible monoamine oxidase-B inhibitors that exert neuroprotective effects in various preclinical models. The aim of the present study was to examine the effect of selegiline and its major metabolite, l-methamphetamine in comparison to rasagiline and its major metabolite, 1-R-aminoindan on oxygen–glucose deprivation induced cell death in nerve growth factor (NGF)-differentiated pheochromocytoma (PC12) cells. Our results show that selegiline reduces oxygen–glucose deprivation induced cell death by 30%. When the cultures were treated with rasagiline at similar concentrations, cell death induced by oxygen–glucose deprivation was reduced by 45–55%. l-methamphetamine, a major selegiline metabolite, but not 1-R-aminoindan, the major rasagiline metabolite, enhanced oxygen–glucose deprivation-induced cell death by 70%. Under normoxic conditions, both metabolites lack neurotoxicity. Concomitant exposure of the cultures under oxygen–glucose deprivation, to a combination of either selegiline and l-methamphetamine or rasagiline and 1-R-aminoindan, indicated that l-methamphetamine, but not 1-R-aminoindan, blocked the neuroprotective effect of the parental drug. These results suggest there may be a neuroprotective advantage of rasagiline over selegiline.
Keywords: Parkinson's disease; Rasagiline; Selegiline; 1-R-aminoindan; l-methamphetamine; Neurotoxicity; Neuroprotection; Oxygen–glucose deprivation;

Parkinson-like extrapyramidal motor side effects associated with the use of antipsychotic drugs, such as increased muscle rigidity, are thought to result from blockade of striatal dopamine D2 receptors. While anticholinergic medications (muscarinic receptor antagonists) ameliorate extrapyramidal side effects, the mechanisms underlying their effectiveness remain unclear. We investigated the site of action of atropine, a non-selective muscarinic receptor antagonist, in reducing increased muscle rigidity, assessed as increases in tonic electromyographic (EMG) activity, induced by the selective dopamine D2 receptor antagonist, raclopride. Atropine significantly reduced raclopride-induced EMG increases in rat hindlimb muscles, when injected into the ventral striatum, but not the dorsal striatum or the substantia nigra. Atropine's site of action was localised to a small area of muscarinic receptors within the ventral part of the striatum, using quantitative autoradiography. These findings provide new information about the regulation of motor control by muscarinic receptor antagonists and additional evidence about the functional heterogeneity of the striatum.
Keywords: Muscarinic receptor antagonist; Antipsychotic drug; Striatum; Muscle rigidity; (EMG) Electromyogram;

Differences in protective profiles of diltiazem isomers in ischemic and reperfused guinea pig hearts by Ryuichi Sato; Kenji Sakamoto; Jun Yamazaki; Taku Nagao (125-131).
The effects of l-cis and d-cis diltiazem on the extracellular potassium concentration ([K+]e), pH and cardiac function were compared in ischemic guinea pig hearts. Before inducing ischemia, l-cis diltiazem (10 and 30 μM) reduced the left ventricular developed pressure (LVDP) with a marginal inhibition of heart rate (HR), whereas lower doses of the d-cis isomer decreased both LVDP and HR. l-cis Diltiazem only slightly inhibited the increase in [K+]e and the decrease in pH but significantly inhibited ischemic contractures in contrast to the marked inhibition of these parameters produced by even low doses of the d-cis isomer. Notably, at equipotent doses for the ischemic parameters, l-cis diltiazem restored the left ventricular end-diastolic pressure (LVEDP) and HR after reperfusion to a greater extent than the d-cis isomer. These results suggest that the l-cis isomer may specifically improve postischemic function, in addition to the modest action on [K+]e and pH, in guinea pig hearts.
Keywords: l-cis Diltiazem; Myocardial ischemia; K+ accumulation; Ca2+ channel blocker; (Guinea pig);

The aim of this study was to investigate the effects of aging on hypotension in vivo and vasorelaxation in vitro induced by calcitonin gene-related peptide (CGRP), using young (3 months old) and elderly (20 and 28 months old) Sprague–Dawley rats. Vasorelaxant responses were measured in isolated rings of rat thoracic aorta and rat caudal artery, which show endothelium-dependent and endothelium-independent responses to CGRP, respectively. The CGRP-induced vasorelaxations were significantly diminished in 28-month-old male rats in both aorta (39.3% of responses in young controls at 10 nM CGRP) and caudal artery (28.5% of responses in young controls at 10 nM CGRP). Acetylcholine caused vasorelaxations in aortic rings of young male rats, but vasocontractions in aortic rings of 28-month-old male rats. Hypotension induced by CGRP was significantly diminished in both 20-month-old male rats (47.7% of young controls) and 20-month-old female rats (34.4% of young controls). Moreover, ovariectomy, known to decrease CGRP-induced hypotension in young female rats, did not further decrease hypotension to CGRP in elderly female rats. In conclusion, vasorelaxant responses in vitro and hypotensive responses in vivo induced by the neuropeptide CGRP are severely impaired in elderly rats as compared to young rats. The data suggest that the vasodilatory responses to CGRP in both large arteries and the small resistance-sized arteries regulating arterial blood pressure are damaged or down-regulated by the aging process.
Keywords: CGRP (calcitonin gene-related peptide); Blood pressure; Gender; Aging; Ovariectomy; Artery;

Raloxifene enhances nitric oxide release in rat aorta via increasing endothelial nitric oxide mRNA expression by Roshanak Rahimian; Gregory P Dubé; Warda Toma; Nancy Dos Santos; Bruce M McManus; Cornelis van Breemen (141-149).
We report the modulatory effects of chronic oral LY139481 (raloxifene) on basal release of nitric oxide (NO) and mRNA levels of endothelial NO synthase (eNOS) in rat thoracic aorta. Constrictor dose–response curves to phenylephrine were generated before and after pretreatment with N ω-nitro-l-arginine methyl ester (l-NAME), an inhibitor of NO synthase. Aortic segments were obtained from four groups of rats gavaged orally for 21 days: (i) ovariectomized, (ii) sham, (iii) ovariectomized estradiol-treated, and (iv) ovariectomized raloxifene-treated. Intact aortic rings from sham rats and ovariectomized rats receiving raloxifene and estrogen showed a greater potentiation of the phenylephrine responses after l-NAME. Semi-quantitative reverse transcription-polymerase chain reaction indicated a gender-based difference in eNOS mRNA expression in thoracic aorta. Moreover, we demonstrated that eNOS mRNA expression in the upper thoracic aorta was significantly higher in treatment groups. These results show that chronically administered raloxifene is exerting a potentially important vasculo-protective effect by stimulating eNOS expression.
Keywords: Estrogen; Raloxifene; Nitric oxide (NO); Nitric oxide (NO) synthase;

Concentration–response curves to noradrenaline (1 nM–100 μM) were obtained in prostates from 6-week streptozotocin diabetic, insulin-treated diabetic or control rats. Compared to the curve obtained in controls, those obtained in prostates from diabetic and insulin-treated diabetic rats were shifted rightward. The α1-adrenoceptor antagonist, prazosin (100 nM), caused a rightward shift of the curves in prostates from all groups. In contrast, the uptake 1 inhibitor, nisoxetine (300 nM), only produced a leftward shift of the curves in prostates from control and insulin-treated diabetic rats. However, frequency–response curves obtained in prostates from both control and diabetic rats were shifted leftward by nisoxetine (300 nM). The concentration–response curve to the α1-adrenoceptor agonist, methoxamine (10 nM–100 μM), obtained in prostates from diabetic rats was shifted rightward compared with controls. Calphostin C (500 nM), a protein kinase C inhibitor, caused a leftward shift of the curve in prostates from diabetic, but not control, rats. The protein kinase C inhibitor, bisindolylmaleimide I (500 nM), β-adrenoceptor antagonist, propranolol (500 nM) and muscarinic cholinoceptor antagonist, atropine (300 nM), had no effect on the noradrenaline concentration–response curves of prostates from control or diabetic rats. Our results suggest that diabetes reduces the sensitivity and reactivity of the prostate to noradrenaline-induced stimulation, and this reduction may be due to changes in protein kinase C activity.
Keywords: Diabetes mellitus; Prostate gland; Benign prostatic hyperplasia; Noradrenaline; Protein kinase C;

Renal effects of glucagon-like peptide in rats by Carol Moreno; Mahesh Mistry; Richard J Roman (163-167).
The present study examined the effects of recombinant glucagon-like peptide-1-(7-36)amide (rGLP-1) on renal hemodynamics and excretory function in innervated and denervated kidneys of anesthetized rats. Intravenous infusion of rGLP-1 at a dose of 1 μg·kg−1·min−1 increased urine flow and Na+ excretion 13-fold in the innervated kidney. The natriuretic and diuretic response to rGLP-1 was attenuated in the denervated kidney in which urine flow and Na+ excretion only increased 3-fold. Fractional excretion of Li+, an index of proximal tubular reabsorption, increased 219% in the innervated kidney but only 54% in the denervated kidney during infusion of rGLP-1. The diuretic and natriuretic response to rGLP-1 was associated with an increase in glomerular filtration rate (39%) in the innervated kidney, but it had no effect on glomerular filtration rate in the denervated kidney. These results indicate that the natriuretic and diuretic effects of rGLP-1 are due to inhibition of Na+ reabsorption in the proximal tubule. It also increases glomerular filtration rate in kidneys with an intact renal innervation.
Keywords: rGLP-1 (glucagon-like peptide-1-(7-36)amide); Kidney; Hemodynamics; Proximal tubule;

KDR-5169, a new gastrointestinal prokinetic agent, enhances gastric contractile and emptying activities in dogs and rats by Shigeki Tazawa; Naoyuki Masuda; Takashi Koizumi; Makio Kitazawa; Tokio Nakane; Hiroshi Miyata (169-176).
KDR-5169, 4-amino-5-chloro-N-[1-(3-fluoro-4-methoxybenzyl)piperidin-4-yl]-2-(2-hydroxyethoxy)benzamide hydrochloride dihydrate, is a new prokinetic with a dual action, i.e., stimulation of the 5-HT4 receptor and antagonism of the dopamine D2 receptor. In this study, we determined in vitro activities of KDR-5169 towards both receptors and demonstrated the effect of the compound on gastrointestinal motor activity in conscious dogs and rats. In dogs, intravenous KDR-5169 stimulated upper gastrointestinal motility in the fasting state and also eliminated the depressive effect of 3,4-dihydroxyphenylalanine (l-DOPA) on this motility in the postprandial state. The effect of KDR-5169 on gastric emptying was further characterized by the use of three rat gastroparesis models (dopamine D2 receptor agonist (quinpirol)-, abdominal surgery-, or combined-situation-induced). Domperidone (a dopamine D2 receptor antagonist) was effective in the quinpirol-delay and combination-delay models, and cisapride and mosapride (5-HT4 receptor agonists) were effective in the surgery-delay model. Only KDR-5169 eliminated the delay of gastric emptying in all three models. In addition, KDR-5169 accelerated emptying to above the normal level in the combination-delay model. These results suggest that KDR-5169 would be effective in various types of gastric ileus caused by different mechanisms.
Keywords: Gastric emptying; KDR-5169; 5-HT4 receptor; Dopamine D2 receptor;

A pyrroloquinazoline derivative with anti-inflammatory and analgesic activity by dual inhibition of cyclo-oxygenase-2 and 5-lipoxygenase by Inmaculada Rioja; M.Carmen Terencio; Amalia Ubeda; Pedro Molina; Alberto Tárraga; Antonia Gonzalez-Tejero; M.José Alcaraz (177-185).
In a previous study, we reported a new pyrroloquinazoline derivative, 3-(4′-acetoxy-3′,5′-dimethoxy)benzylidene-1,2-dihydropyrrolo[2,1-b]quinazoline-9-one (PQ), which inhibited human purified 5-lipoxygenase activity and prostaglandin E2 release in lipopolysaccharide-stimulated RAW 264.7 cells. In the present work, we show that PQ inhibits cyclo-oxygenase-2 activity in intact cell assays (human monocytes) and purified enzyme preparations (ovine isoenzymes) without affecting cyclo-oxygenase-1 activity. This behaviour was confirmed in vivo by using the zymosan-injected mouse air pouch model, where PQ caused a marked reduction in cell migration and leukotriene B4 levels at 4 h, as well as inhibition of prostaglandin E2 levels without affecting cyclo-oxygenase-2 expression at 24 h after zymosan stimulation. In addition, oral administration of this compound significantly reduced carrageenan-induced mouse paw oedema and phenyl-p-benzoquinone-induced writhings in mice. These results indicate that oral PQ exerts analgesic and anti-inflammatory effects, which are related to dual inhibition of cyclo-oxygenase-2 and 5-lipoxygenase activities.
Keywords: Pyrroloquinazoline; Eicosanoid; Cyclo-oxygenase-2; Air pouch; Carrageenan paw oedema; Analgesia;

Participation of prostaglandin E2 and platelet-activating factor in thapsigargin-induced production of interleukin-6 by Gaku Ichinowatari; Masateru Yamada; Hiroshi Yaginuma; Kousei Tsuyuki; Atsuo Tanimoto; Kazuo Ohuchi (187-196).
Incubation of rat peritoneal macrophages in the presence of thapsigargin increased production of prostaglandin E2, intracellular platelet-activating factor (PAF) and interleukin-6. However, no PAF was detected in the conditioned medium. In the presence of SK&F 98625 (diethyl 7-(3,4,5-triphenyl-2-oxo-2,3-dihydroimidazol-1-yl)heptane phosphonate), a CoA-independent transacylase inhibitor, the thapsigargin-induced increases in the interleukin-6 mRNA level and interleukin-6 production were suppressed in a concentration-dependent manner. This inhibitor also suppressed the production of prostaglandin E2 and intracellular PAF. The PAF receptor antagonists such as E6123 ((S)-(+)-6-(2-chlorophenyl)-3-cyclopropanecarbonyl-8,11-dimethyl-2,3,4,5-tetrahydro-8H-pyrido[4′,3′:4,5]thieno[3,2-f][1,2,4]triazolo [4,3-a][1,4]diazepine) and L-652,731 (2,5-bis(3,4,5-trimethylphenyl)tetrahydrofuran) partially inhibited the thapsigargin-induced increase in the levels of interleukin-6 mRNA and interleukin-6 protein. The SK&F 98625-induced suppression of interleukin-6 mRNA accumulation and interleukin-6 production was partially restored by addition of exogenous prostaglandin E2. However, exogenous PAF failed to reverse the suppression suggesting that the intracellular PAF does not act in an autocrine mechanism. These findings suggested that the concurrently produced prostaglandin E2 and intracellular PAF participate in the thapsigargin-induced increase in the interleukin-6 mRNA level and interleukin-6 production by rat peritoneal macrophages.
Keywords: PAF (platelet-activating factor); Interleukin-6; Prostaglandin E2; Thapsigargin; SK&F 98625; Macrophage;

Chronic acarbose-feeding increases GLUT1 protein without changing intestinal glucose absorption function by Leonardo Paiva; Ralf Binsack; Ubiratan Fabres Machado (197-204).
As α-glucosidase inhibitor, the antidiabetic drug acarbose reduces postprandial glucose levels by retarding the intestinal digestion of polysaccharides. However, it is unknown if acarbose also affects the expression of intestinal glucose transporters, especially the Na+-glucose cotransporter (SGLT1) and the glucose transporters GLUT1 and GLUT2. To unravel this question, Wistar rats received standard powdered chow either without (control) or with acarbose (40 mg acarbose/100 g chow) for 40 days. While food intake was slightly enhanced by acarbose, the drug had no influence on weight gain or plasma glucose and insulin levels. The acarbose-treatment did not alter the SGLT1 and GLUT2 gene expression in both upper and middle small intestine, whereas GLUT1 protein was increased by 75% in middle small intestine. Despite the territorial change in GLUT1 protein, the intestinal glucose absorption in an acarbose-free perfusion study was unaltered. In conclusion, the chronic use of acarbose did not alter the acarbose-free glucose absorption profile.
Keywords: Acarbose; Intestinal glucose transport; SGLT1; GLUT1; GLUT2; Diabetes mellitus;

Author index (205-206).

Keyword index (207-211).