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Eur J Pharmacol [journal]
- Characterization of a novel Vasopressin V1b receptor antagonist, V1B-30N, in animal models of anxiety-like and depression-like behavior. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Mar 3.
Overactivity of the hypothalamic-pituitary-adrenal (HPA) axis has been linked to affective disorders such as anxiety and depression. Dampening HPA activity has, therefore, been considered as a possible means of treating affective disorders. Given the important role of vasopressin in modulating the HPA axis, one strategy has focused on inhibiting activity of the Vasopressin 1b (V1b) receptor. In animals, V1b receptor antagonists reduce plasma stress hormone levels and have been shown to have an anxiolytic-like effect. Recently, V1B-30N was identified as a highly potent V1b receptor antagonist with selectivity over other vasopressin receptors, which is evaluated here in rodent models of anxiety-like and depression-like behaviors. V1B-30N (1-30mg/kg, IP) dose-dependently reduced separation-induced vocalizations in rat pups without producing any sedative effects in the animals. Similarly, V1B-30N (3-30mg/kg, IP) dose- dependently reduced separation-induced vocalizations in guinea pig pups. In a conflict assay, conditioned lick suppression, V1B-30N (3-30mg/kg, IP) increased punished licking. To assess antidepressive-like properties, V1B-30N (1-30mg/kg) was tested in the mouse and rat forced-swim tests but was found to be inactive. These results are consistent with previous findings with other V1b antagonists, which suggest that acute pharmacological antagonism of the V1b receptor has anxiolytic-like but not antidepressant-like properties.
- Mechanisms of angiotensin converting enzyme inhibitor-induced IOP reduction in normotensive rats. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 26.
Angiotensin converting enzyme inhibitors (ACEIs) have been shown to lower intraocular pressure (IOP). Since, the ACEIs cause increased tissue prostaglandin levels, we hypothesized that the mechanisms of ACEI-induced IOP reduction have similarity with those of prostaglandin analogs. The present study investigated the involvement of matrix metalloproteinases (MMPs) and cytokine activity modulation as the underlying mechanisms of ACEI-induced ocular hypotension. The IOP lowering effect of single drop of enalaprilat dehydrate 1% was evaluated in rats pretreated with a broad spectrum MMP inhibitor or a cytokine inhibitor. Effect of angiotensin receptor blocker, losartan potassium 2%, was also studied to evaluate involvement of angiotensin II receptor type 1 (AT1) in IOP lowering effect of ACEI. Topical treatment with single drop of enalaprilat resulted in significant IOP reduction in treated eye with mean peak reduction 20.3% at 3h post-instillation. Treatment with losartan resulted in a peak IOP reduction of 13.3%, which was significantly lower than enalaprilat, indicating involvement of mechanisms in addition to AT1 blockade. Pretreatment with a broad spectrum MMP inhibitor or a cytokine inhibitor significantly attenuated the enalprilat-induced IOP reduction with mean peak IOP reduction 11.2% and 13.6% respectively. The IOP-lowering effect of enalaprilat seems to be attributed to reduced angiotensin II type 1 receptor stimulation and modulation of MMP and cytokines activities.
- Valproic acid inhibits excess dopamine release in response to a fear-conditioned stimulus in the basolateral complex of the amygdala of methamphetamine-sensitized rats. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 26.
Valproic acid, an established antiepileptic and antimanic drug, has recently emerged as a promising emotion-stabilizing agent for patients with psychosis. Although dopamine transmission in the amygdala plays a key role in emotional processing, there has been no direct evidence about how valproic acid acts on the dopaminergic system in the brain during emotional processing. In the present study, we tested the effect of valproic acid on a trait marker of vulnerability to emotional stress in psychosis, which is excess dopamine release in response to a fear-conditioned stimulus (CS) in the basolateral complex of the amygdala of methamphetamine-sensitized rats. Extracellular dopamine was collected from the amygdala of freely moving methamphetamine-sensitized rats by in vivo microdialysis and was measured using high-performance liquid chromatography. During microdialysis, valproic acid was intraperitoneally injected followed by CS exposure. Valproic acid treatment decreased baseline levels of dopamine and also attenuated the excess dopamine release in response to the CS in the amygdala of methamphetamine-sensitized rats. The results prove that valproic acid inhibits spontaneous dopamine release and also attenuates excess dopaminergic signaling in response to emotional stress in the amygdala. These findings suggest that the mechanisms of the emotion-stabilizing effect of valproic acid in psychosis involve modulation of dopaminergic transmission in emotional processing.
- Pioglitazone, a PPARγ agonist, provides comparable protection to angiotensin converting enzyme inhibitor ramipril against adriamycin nephropathy in rat. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 27.
Peroxisome proliferator-activated receptor γ (PPARγ) agonists have been shown to ameliorate diabetic nephropathy, but much less is known about their effects in non-diabetic nephropathies. In the present study, metabolic parameters, blood pressure, aortic endothelial function along with molecular and structural markers of glomerular and tubulointerstitial renal damage, were studied in a rat model of normotensive nephropathy induced by adriamycin and treated with PPARγ agonist pioglitazone (12mg/kg, po), angiotensin converting enzyme (ACE) inhibitor ramipril (1mg/kg, po) or their combination. Pioglitazone had no effect on systolic blood pressure, marginally reduced glycemia and improved aortic endothelium-dependent relaxation. In the kidney, pioglitazone prevented the development of proteinuria and focal glomerulosclerosis to the similar extent as blood-pressure lowering ramipril. Renoprotection provided by either treatment was associated with a reduction in the cortical expression of profibrotic plasminogen activator inhibitor-1 and microvascular damage-inducing endothelin-1, and a limitation of interstitial macrophage influx. Treatment with PPARγ agonist, as well as ACE inhibitor comparably affected renal expression of renin-angiotensin system (RAS) components, normalizing increased renal expression of ACE and enhancing the expression of Mas receptor. Interestingly, combined pioglitazone and ramipril treatment did not provide any additional renoprotection. These results demonstrate that in a nondiabetic renal disease, such as adriamycin-induced nephropathy, PPARγ agonist pioglitazone provides renoprotection to a similar extent as an ACE inhibitor by interfering with the expression of local RAS components and attenuating related profibrotic and inflammatory mechanisms. The combination of the both agents, however, does not lead to any additional renal benefit.
- Thyroid hormone exacerbates vasoconstriction in insulin resistance: The role of ONOO(-) [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 25.
Insulin resistance has been proposed to play a pivotal role in vasoconstriction due to increased oxidative stress. Hyperthyroidism would amplify cardiovascular disease risk in diabetic patients, though thyroid hormone advance vascular relaxation and reduce vascular contraction by virtue of NO production in vascular smooth muscle cells (VSMCs). Thus, we aimed to investigate the vascular tone and its underlying mechanism in insulin resistance accompanied by hyperthyroidism. Vascular reactivity studies showed that endothelium-denuded thoracic aortic rings from rats fed with high-fat high-sucrose (HFHS) diet and L-T4 (HFHS+L-T4) exhibited a stronger contractile response to noradrenaline than HFHS rats, which was reversed by L-NAME and GSH. Furthermore, rat thoracic aortic smooth muscle cells (A10) simultaneously stimulated with high glucose insulin (high Glc/Ins) and T3 demonstrated lower NO, superoxide anion ( [Formula: see text] ) levels, and higher iNOS, nitrite ( [Formula: see text] ), peroxynitrite (ONOO(-)) levels than that treated with T3 only. Excessive ONOO(-) markedly aggravated oxidative stress. Thus, we hypothesized that the elevated concentration of ONOO(-) which is generated by NO and [Formula: see text] could be critically instrumental in the progression of vasoconstriction by increasing oxidative stress.
- The immunomodulatory and anti-apoptotic effect of dexamethasone in imminent preterm labor: An experimental study. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 26.
The study was designed to investigate the effect of dexamethasone (DEX) on the latency period to delivery in a murine model of preterm labor. To this purpose, pregnant mice were randomly assigned in groups: the control group received water for injection (n=20), the preterm labor group was injected with lipopolysaccharide (LPS) (n=22), while the glucocorticoids group was administered DEX either 1h before (n=17) or after (n=7) lipopolysaccharide. In a first set of experiments animals were monitored to record perinatal outcomes. In another set of experiments, the remaining animals were sacrificed eight h after interventions. Fetuses were homogenized to measure tumor necrosis alpha in supernatants. Maternal splenocytes were isolated and stimulated for cytokine production. Serum of mice was incubated with donor cells from healthy pregnant and non-pregnant animals to induce apoptosis. LPS induced preterm labor but treatment or pretreatment with DEX delayed parturition exerting a favorable impact on survival of delivered fetuses. DEX inverted the increase of fetoplacental tumor necrosis alpha levels. Serum of LPS-stimulated mice induced apoptosis of splenocytes of either pregnant or non-pregnant healthy mice; this was reversed after incubation of splenocytes with serum coming from DEX pre-treated mice. The presented findings suggest that DEX administered either as pre-treatment or treatment prolonged gestation and promoted neonatal survival in a sterile murine model of preterm labor. These favorable outcomes were closely linked to alterations in both immune and apoptotic responses of animals.
- Increase of glucocorticoids is not required for the acquisition, but hinders the extinction, of lithium-induced conditioned taste aversion. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 25.
Lithium chloride at doses sufficient to induce conditioned taste aversion (CTA) causes c-Fos expression in the paraventricular nucleus and increases the plasma level of corticosterone with activation of the hypothalamic-pituitary-adrenal axis. This study was conducted to define the role of glucocorticoid in the acquisition and extinction of lithium-induced CTA. In experiment 1, Sprague-Dawley rats received dexamethasone (2mg/kg) or RU486 (20mg/kg) immediately after 5% sucrose access, and then an intraperitoneal injection of isotonic lithium chloride (12ml/kg) was followed with 30min interval. Rats had either 1 or 7 days of recovery period before the daily sucrose drinking tests. In experiment 2, rats were conditioned with the sucrose-lithium pairing, and then received dexamethasone or vehicle at 30min before each drinking test. In experiment 3, adrenalectomized (ADX or ADX+B) rats were subjected to sucrose drinking tests after the sucrose-lithium pairing. Dexamethasone, but not RU486, pretreatment blunted the formation of lithium-induced CTA memory. Dexamethasone prior to each drinking test suppressed sucrose consumption and prolonged the extinction of lithium-induced CTA. Sucrose consumption was significantly suppressed not only in ADX+B rats but also in ADX rats during the first drinking session; however, a significant decrease was found only in ADX rats on the fourth drinking session. These results reveal that glucocorticoid is not a necessary component in the acquisition, but an important player in the extinction, of lithium-induced CTA, and suggest that a pulse increase of glucocorticoid may hinder the extinction memory formation of lithium-induced CTA.
- Elevated melatonin levels in natalizumab-treated female patients with relapsing-remitting multiple sclerosis: Relationship to oxidative stress. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 25.
Natalizumab is currently the most successful clinical treatment for multiple sclerosis. The use of this drug is associated with the reduction in the number of relapses and a slowing in disease progression, as well as an improvement in signs and symptoms displayed by the patients. To evaluate the effect of natalizumab on melatonin and its relationship with peripheral oxidative damage, we studied the serum melatonin levels in 18 patients with relapsing-remitting multiple sclerosis. Natalizumab caused significant increases in serum melatonin concentrations. This change was associated with a rise in increase of antioxidants and a reduction in oxidative stress biomarkers. In conclusion, these data may explain, at least in part, some of the beneficial effects exhibited by disease antibody such as its antioxidant capacity.
- 1,2,3,4-Tetrahydroisoquinoline produces an antidepressant-like effect in the forced swim test and chronic mild stress model of depression in the rat: Neurochemical correlates. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 20.
1,2,3,4-Tetrahydroisoquinoline (TIQ) is an exo- and endogenous amine naturally present in mammalian brain which displays antidepressant-like effect in various animal models: the forced swim test (FST) and chronic mild stress (CMS) paradigm in rats. To elucidate this action we compared the effects of TIQ with imipramine, a classic antidepressant drug and one of the most clinically effective. Applied behavioral tests showed that TIQ produced an antidepressant-like effect with a potency comparable to that of imipramine. TIQ (25-50mg/kg i.p.), similarly to imipramine (10-30mg/kg i.p.), reduced the immobility time in FST and completely reversed the decrease in sucrose intake caused by CMS in the rat. In addition, in order to avoid the possible psychostimulating effect of TIQ we examined the influence of its administration on locomotor activity in rats. TIQ, like imipramine, produced a reduction in horizontal locomotor activity. This suggested that TIQ did not have psychostimulant properties and that prolonged swimming in the FST was a result of an increased motivation to escape from the stressful situation. The biochemical analyses have shown that TIQ activates monoaminergic systems as a reversible monoamine oxidase (MAO) inhibitor and free radical scavenger. Beyond the activation of noradrenaline and serotonin systems, TIQ also moderately affects the dopamine system. On the basis of the presented behavioral and biochemical studies we suggest that TIQ is a potential new antidepressant which may be effective for the depression therapy in a clinical setting.
- Effects of dopamine D2-like receptor agonists in mice trained to discriminate cocaine from saline: Influence of feeding condition. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Feb 20.
In rats, the discriminative stimulus effects of direct- and indirect-acting dopamine receptor agonists are mediated by multiple dopamine receptor subtypes and the relative contribution of dopamine D2 and D3 receptors to these effects varies as a function of feeding condition. In these studies, free-fed and food-restricted mice were trained to discriminate 10.0mg/kg cocaine using a two-lever discrimination procedure in which responding was maintained by food. Both groups of mice acquired the discrimination; however, free-fed mice responded at lower rates than food-restricted mice. Dopamine D3 receptor agonists, pramipexole and quinpirole, increased cocaine-appropriate responding (>85%) in food-restricted, but not in free-fed mice. The dopamine D2 receptor agonist, sumanirole, and the nonselective dopamine receptor agonist, apomorphine, failed to increase cocaine-appropriate responding in either group. Free-fed mice were more sensitive than food-restricted mice to the rate-decreasing effects of dopamine receptor agonists and these effects could not be overcome by increasing the magnitude of reinforcement. Because feeding condition did not alter quinpirole-induced hypothermia, it is unlikely that differences in the discriminative stimulus or rate-decreasing effects of dopamine D2-like receptor agonists were due to differences in the pharmacokinetic properties of the drugs. Although these results suggest that the discriminative stimulus effects of cocaine are mediated by both dopamine D2 and D3 receptors in food-restricted mice, the increased sensitivity of free-fed mice to the rate-decreasing effects of dopamine D2-like receptor agonists limited conclusions about the impact of feeding conditions on the relative contribution of dopamine D2 and D3 receptors to the discriminative stimulus effects of cocaine.