Autonomic and Autacoid Pharmacology最新文献

1. This study was conducted to determine whether the atypical opioid analgesic tramadol inhibits the contractility of isolated non-pregnant human myometrium. Ten strips of non-pregnant human myometrium stimulated with 55 mm potassium chloride (KCl) were treated with three concentrations (30, 100 and 300 μm) of tramadol to test for any inhibitory effect of tramadol. The effects of concurrent administration of the ß adrenoceptor antagonist propranolol (1 μm), the guanylyl cyclase and nitric oxide synthase inhibitor methylene blue (20 μm) and the opioid receptor antagonist naloxone (100 μm) with tramadol were also studied.
2. Tramadol caused a concentration-dependent inhibition of KCl-induced myometrial contractility, which was statistically significant at all three concentrations of tramadol used. Propranolol significantly reversed the inhibitory effect of 100 μm tramadol on KCl-induced myometrial contractility but not that of 300 μm tramadol. Neither methylene blue nor naloxone reversed the inhibitory effect of tramadol on KCl-induced myometrial contractility.
3. These results suggest that tramadol inhibits KCl-induced contractility of isolated human myometrium. They also suggest that tramadol relaxes the myometrium due to stimulation of ß₁ adrenoceptors. However, the concentrations of tramadol required to relax the myometrium were high and likely to be attained at toxic doses, rather than therapeutic doses, of tramadol.

1. Acetylcholine, and to a lesser extent ATP, mediates neurogenic contractions of bladder smooth muscle. Recently, the urothelium and lamina propria have also been shown to have contractile properties, but the neurotransmitters involved in mediating responses to nerve stimulation have not been investigated.
2. Isolated strips of porcine urothelium with lamina propria were electrically field stimulated and contractions recorded. Drugs interfering with neurotransmission were then employed to identify which neurotransmitters mediated responses.
3. Strips of urothelium/lamina propria developed spontaneous contractions with a frequency of 3.5 ± 0.1 cycles min⁻¹ and amplitude of 0.84 ± 0.06 g. Electrical field stimulation at 5, 10, and 20 Hz resulted in frequency-related contractions (1.13 ± 0.36 g, 1.59 ± 0.46 g and 2.20 ± 0.53 g, respectively, n = 13), and these were reduced in the presence of tetrodotoxin (1 μm) by 77 ± 20% at 5 Hz, 79 ± 7% at 10 Hz and 74 ± 12% at 20 Hz (all P < 0.01), indicating they were predominantly neurogenic in nature.
4. Neither the muscarinic antagonist atropine (10 μm), the adrenergic neurone blocker guanethidine (10 μm) nor desensitization of the purinergic receptors with α,β-methylene ATP (10 μm) affected the contractile amplitude. Similarly, responses were not affected by the nitric oxide synthase inhibitor l-NNA (100 μm) or drugs that interfere with peptide neurotransmission (capsaicin, NK2 antagonist GR159897, protease inhibitors).
5. In conclusion, electrical depolarization of the nerves present in the porcine urothelium/lamina propria results in frequency-dependent contractions, which are predominantly neurogenic in nature. These contractions are resistant to drugs that inhibit the adrenergic, cholinergic and purinergic systems. The neurotransmitter involved in the responses of this tissue is therefore unknown but does not appear to be a peptide.

1. Diabetes mellitus can lead to neuropathy of enteric neurons, resulting in abnormal gut motility. These studies investigated voltage-dependent contributions of muscarinic M₃ receptor activation by acetylcholine and neurokinin NK₁ receptor activation by neurokinins to nerve-stimulated contractions of longitudinal ileal strips from STZ guinea-pigs, a type 1 diabetic model with insulin deficiency, but mild hyperglycaemia.
2. Contractions to bethanechol, substance P methyl ester, and nerve stimulation were greater in diabetic as compared to control ileum.
3. The muscarinic M₃ receptor antagonist 4-DAMP at lower voltages and the neurokinin NK₁ receptor antagonist SR140333 at higher voltages, but not the neurokinin NK₁ receptor antagonist CP-96,345, were more effective at inhibiting nerve-stimulated immediate peak contractions and total areas of contraction of ileum from diabetic as compared to control animals. For diabetic ileum, voltage-dependent increases in the areas of nerve-stimulated contraction were observed in the presence of 4-DAMP and CP-96,345 but not SR140333.
4. At low voltages only, nerve-stimulated release of acetylcholine was greater from diabetic as compared to control ileum.
5. Fluorescence intensity of tachykinin-like immunoreactivity was increased in ileal myenteric ganglia from diabetic as compared to control animals.
6. In diabetic guinea-pigs, stronger ileal nerve-stimulated contractions reflected increased release of acetylcholine at lower voltages and tachykinins at higher voltages, as well as increased sensitivity of smooth muscle M₃ and NK₁ receptors to acetylcholine and tachykinins. Hypoinsulinaemia may be a primary contributor to intestinal motility dysfunction in type 1 diabetes mellitus.

1. We investigated captopril effects, an ACE inhibitor, on hypertension development, on Ang II and Ang-(1-7) plasma concentrations, on Ang II-induced contraction in isolated kidneys, and on kidney AT1R from spontaneously hypertensive (SHR) rats.
2. Five weeks-old SHR and Wistar Kyoto (WKY) rats were treated with captopril at 30 mg/kg/day, in drinking water for 2 or 14 weeks. Systolic blood pressure (SBP) was measured, and isolated kidneys were tested for perfusion pressure and AT1R expression; while Ang II and Ang-(1-7) concentrations were determined in plasma.
3. Captopril did not modify SBP in WKY rats and avoided its increase as SHR aged. Plasma Ang-II concentration was ∼4-5 folds higher in SHR rats, and captopril reduced it (P < 0.05); while captopril increased Ang-(1-7) by ∼2 fold in all rat groups.
4. Captopril increased Ang II-induced pressor response in kidneys of WKY and SHR rats, phenomenon not observed in kidneys stimulated with phenylephrine, a α₁-adrenoceptor agonist.
5. Captopril did not modify AT1R in kidney cortex and medulla among rat strains and ages.
6. Data indicate that captopril increased Ang II-induced kidney perfusion pressure but not AT₁R density in kidney of WKY and SHR rats, due to blockade of angiotensin II synthesis; however, ACE inhibitors may have other actions like activating signaling processes that could contribute to their diverse effects.

1. In mouse atrium, M₂ and M₃ muscarinic receptors (M₂R and M₃R) are involved in biphasic (negative and positive) inotropic actions of muscarinic agonists, and the positive inotropic action is reduced by indomethacin. The aim of our study was to determine the localization of M₂R, M₃R and cyclo-oxygenase (COX) in mouse atrium and to characterize muscarinic receptor-mediated positive inotropy.
2. M₂R immunoreactivity was found only on atrial myocardium, but M₃R immunoreactivity was localized on both the myocardium and endocardial endothelium. COX-1 and COX-2 immunoreactivities were identified in both myocardial and endocardial endothelium.
3. In electrically stimulated left atria, carbachol caused M₂R-mediated negative inotropy followed by M₃R-mediated positive inotropy. Removal of atrial endothelium reduced the positive inotropy without affecting the negative inotropy, suggesting that stimulation of endothelial M₃R mediates the positive inotropy.
4. N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS398, COX-2 inhibitor) decreased the carbachol-induced positive inotropy; however, 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC560, COX-1 inhibitor), 1-[[4,5-bis(4-methoxyphenyl)-2-thiazolyl]carbonyl]-4-methylpiperazine (FR122047, COX-1 inhibitor) and l-nitroarginine methylester did not affect the inotropic response.
5. M₃R activation caused positive chronotropy in spontaneously beating right atria when M₂R-mediated negative chronotropy was suppressed and rate of contraction was low, <350 beats min⁻¹.
6. Our results indicate that although M₃Rs are located on both myocardial cells and endocardial endothelial cells, only endothelial M₃Rs mediate positive inotropy in response to muscarinic agonists via activation of COX-2 in the mouse atrium. M₃R-mediated positive chronotropy counteracting M₂R-mediated negative chronotropy was also demonstrated.

1 Metformin is a hypoglycaemic drug currently used to increase insulin sensitivity in the treatment of type 2 diabetes and metabolic syndrome. Its main mechanism of action is through activation of AMP-activated protein kinase, an enzyme that regulates cellular and whole organ metabolism.

2 The fructose-overloaded rat is an experimental model with features that resemble human metabolic syndrome. We have previously reported alterations in vascular prostanoids (PR) in this model.

3 The aim of this study was to analyse the effects of metformin treatment on blood pressure, metabolic parameters and PR production in aorta and mesenteric vascular bed (MVB) from fructose-overloaded animals. Four groups of male Sprague–Dawley rats were used: control, fructose overloaded (10% w/v fructose), metformin treated (50 mg kg⁻¹ day⁻¹) and fructose-overloaded treated with metformin.

4 Rats with fructose overload had significantly elevated systolic blood pressure, glycaemia, triglyceridaemia, cholesterolaemia and insulinaemia compared with controls. Except for insulinaemia, metformin limited all these increases in fructose-overloaded animals.

5 Fructose overload reduced prostacyclin levels in aorta and MVB, but prostaglandin E₂ levels were only reduced in MVB. Metformin treatment reduced the levels of the vasoconstrictor prostaglandins, PGF₂α and thromboxane, in both vascular preparations from fructose-overloaded rats. PGF₂α levels were significantly reduced by metformin in controls.

6 In conclusion, one of the mechanisms by which metformin reduced blood pressure in this model is by decreasing vasoconstrictor prostaglandin production.

1 The atypical opioid analgesic tramadol has been shown to provide beneficial clinical and urodynamic effects in patients with detrusor overactivity. The effect of tramadol on isolated detrusor muscle has not been studied. This study investigated the ability of tramadol to inhibit acetylcholine (ACh)-induced contractility of the isolated caprine (goat) detrusor muscle. The effect of three concentrations (30, 100 and 300 μm) of tramadol on 10 caprine detrusor strips contracted by the addition of 100, 200 or 400 μm ACh was studied. The sensitivity of tramadol-induced inhibition of ACh responses to treatment with the β-adrenoceptor antagonist propranolol (1 μm) and the opioid receptor antagonist naloxone (100 μμ) was also studied.

2 Tramadol caused a concentration-dependent inhibition of ACh-induced detrusor contraction that was reversed by raising the concentration of ACh. Propranolol, but not naloxone, reversed the tramadol-induced inhibition of contractions to ACh in the detrusor.

3 These results suggest that tramadol inhibits ACh-induced contractility of the isolated detrusor. They also suggest that tramadol does so by an indirect anticholinergic mechanism involving the stimulation of β-adrenoceptors. Tramadol may be useful in managing clinical conditions requiring relaxation of the detrusor muscle. Although the concentrations of tramadol needed to relax the detrusor were relatively high, these could be clinically attained via intravesical administration.

1 In cardiac surgery, agents are needed to produce temporary cardiac arrest (cardioplegia). One of these agents is esmolol (ESM) which is a short-acting selective beta-1 adrenergic receptor antagonist and its overdose causes diastolic ventricular arrest.

2 The ²⁵MgPMC₁₆ (porphyrin adducts of cyclohexil fullerene-C60) is known as a nanoparticle which has a cardioprotective effect when the heart is subjected to stressful conditions.

3 In this study, we aimed to confirm the deleterious effects of ESM overdose on cardiac mitochondria and identify any protective effects of ²⁵MgPMC₁₆ in male Wistar rats. Esmolol 100 mg kg⁻¹ (LD50 = 71 mg kg⁻¹) was injected intravenously (i.v.) into tail vein to induce cardiac arrest. This dose was obtained from an ESM dose–response curve which induces at least 80% arrest in rats.

4 ²⁵MgPMC₁₆ at three different doses (45, 90 and 224 mg kg⁻¹) was injected i.v. as pretreatment, eight hours before ESM injection. ²⁵MgCl₂ or ²⁴MgPMC₁₆ were used as controls. Following cardiac arrest, the heart was removed and the mitochondria extracted. Mitochondrial viability and the adenosine 5′-diphosphate sodium salt hydrate/Adenosine 5′-triphosphate disodium salt hydrate (ADP/ATP) ratio were measured as biomarkers of mitochondrial function.

5 Results indicate that ²⁵MgPMC₁₆ caused a significant increase in mitochondrial viability and decrease in ADP/ATP ratio. No significant changes were seen with ²⁴MgPMC₁₆ or ²⁵MgCl₂. It is concluded that cardiac arrest induced by ESM overdose leads to a significant decrease in mitochondrial viability and their ATP levels, whereas pretreatment by ²⁵MgPMC₁₆ can protect mitochondria by increasing ATP level through liberation of Mg into cells and the improvement of hypoxia.

1 Levels of IL-13, IL-1β and TNF-α are increased in bronchial lavage fluid of asthmatics and induce certain significant features of bronchial asthma including airway hyper-responsiveness (AHR). In this study, we have investigated the effect of these cytokines in naïve mice and those sensitized to ovalbumin (OVA) on bronchoconstrictions to methacholine (MCh) and the functional antagonism induced by β₂-adrenoceptor agonism.

2 Naïve or OVA-sensitized mice were treated for 3 days with IL-1β (250 U), TNF-α (150 ng), IL-13 (5 μg) or combinations of IL-1β with TNF-α or IL-1β with IL-13. MCh-induced bronchoconstriction and its sensitivity to albuterol, a β₂-adrenoceptor agonist, was assessed 24 h after the last cytokine administration.

3 In naïve mice, responsiveness to MCh was significantly increased by the combination of IL-1β and TNF-α, IL-13 alone or in combination with IL-1β, but not by treatment with IL-1β or TNF-α alone. Similar results were obtained in OVA-sensitized mice except that treatment with IL-13 alone did not increase sensitivity to MCh.

4 In naïve mice, albuterol sensitivity was only significantly attenuated by treatment with IL-1β and TNF-α in combination. In mice sensitized to OVA, albuterol sensitivity was significantly attenuated by treatment with TNF-α, IL-13 or IL-13 in combination with IL-1β.

5 Inflammatory cell influx was increased by all cytokines and combinations except IL-13 in OVA-sensitized mice.

6 Our data do not support a link between inflammatory cell influx and AHR. In addition, the mechanism of IL-13-induced AHR might involve decreased β₂-adrenoceptor responsiveness.

1 The pressor action of the α_1A-adrenoceptor (α_1A-AR) agonist A61603 (N-[5-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl] methanesulfonamide) and the α₁-ARs agonist phenylephrine and their blockade by selective α₁-ARs antagonists in the isolated mesenteric vascular bed of wild-type (WT) mice and α_1D-AR knockout (KO α_1D-AR) mice were evaluated.

2 The apparent potency of A61603 to increase the perfusion pressure in the mesenteric vascular bed of WT and KO α_1D-AR mice is 86 and 138 times the affinity of phenylephrine, respectively.

3 A61603 also enhanced the perfusion pressure by ≈1.7 fold in the mesenteric vascular bed of WT mice compared with KO α_1D-AR mice.

4 Because of its high affinity, low concentrations of the α_1A-AR selective antagonist RS100329 (5-methyl-3-[3-[4-[2-(2,2,2,-trifluoroethoxy) phenyl]-1-piperazinyl] propyl]-2,4-(1H)-pyrimidinedione) shifted the agonist concentration–response curves to the right in the mesenteric vascular bed of WT and KO α_1D-AR mice.

5 The α_1D-AR selective antagonist BMY7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5] decane-7,9-dione) did not modify the A61603 or the phenylephrine-induced pressor effect.

6 The α_1B/D-ARs alkylating antagonist chloroethylclonidine (CEC) shifted the agonist concentration–response curves to the right and decreased the maximum phenylephrine-induced vascular contraction in KO α_1D-AR mice when compared to WT mice; however, CEC only slightly modified the contraction induced by A61603.

7 The results indicate that the isolated mesenteric vascular bed of WT and KO α_1D-AR mice expresses α_1A-AR, that the pressor action of α_1A-AR is up-regulated for α_1D-AR in WT mice and suggest an important role of α_1B-AR in the vascular pressure evoked by phenylephrine in KO α_1D-AR mice.