Effects of dextromethorphan on in vitro contractile responses of mouse and rat urinary bladders

PURPOSE: Dextromethorphan (DXM) is a cough-suppressing ingredient in a variety of over-the-counter cough and cold medications. Dextromethorphan elevates the threshold for coughing primarily through a central mechanism. At doses recommended for treating coughs the drug is safe and effective. At much higher doses, DXM produces dissociative effects similar to those of phencyclidine and ketamine. Opioid analgesics structurally related to DXM also inhibit bladder contractions and produce urinary retention through a non-opioid mechanism. This study evaluated the direct effects of DXM on in vitro contractile responses of rat and mouse urinary bladders. METHODS: Male rats and mice were anaesthetized and their bladders removed. Bladder strips were suspended in 15 ml oxygenated Tyrode's solution containing glucose. Bladder strip contractions were evoked by field stimulation (FS), carbachol or elevated KCl concentrations and contractile responses recorded. The strips were then exposed to 3 microM (DXM) for 30 min and re-stimulated. This sequence was repeated at 10, 30, and 100 microM DXM. RESULTS: (a) The rat bladder generated significantly greater tension than the mouse bladder. (b) Dextromethorphan produced a dose-dependent inhibition of the response to FS that was approximately equal for rat and mouse bladders. FS at 8 or 32 Hz was significantly more sensitive to DXM inhibition than 2 Hz. (c) The response to carbachol was more sensitive to inhibition by DXM than the responses to FS or KCl. CONCLUSIONS: These results demonstrate that DXM inhibits bladder contractions in vitro and that mouse and rat bladders are affected to approximately the same extent.     

Effect of nifedipine on the contractile responses of the isolated rat bladder

The effect of the calcium channel blocker nifedipine on the motor transmission in isolated preparations of rat detrusor smooth muscle has been studied. Nifedipine blocked the major part (75 to 80%) of the contractile response to electrical field stimulation, while atropine only blocked 20 to 25%. In preparations pretreated with atropine, the response to electrical field stimulation was completely abolished by nifedipine. The converse was also true; in preparations pretreated with nifedipine the response was fully blocked by atropine. The nifedipine-resistant response was greatly potentiated by the anticholinesterase eserine. The blocking action of nifedipine on motor transmission was partially antagonised by raising Ca2(+)-concentration. Acetylcholine concentration-response curve was shifted to the right by nifedipine. It is concluded that the non-cholinergic motor neurotransmitter evokes contraction of the rat detrusor smooth muscle by activating external Ca2(+)-transport channels whereas the cholinergic contraction is mediated partly or wholly by alternative mechanisms.     

Calcium channel blockade and contractile responses in the isolated human vas deferens

The effects of removal of extracellular calcium and of the calcium channel blockers nifedipine, verapamil and diltiazem were studied on contractions induced by electrical field stimulation and high K+-solution in isolated preparations of the human vas deferens. Electrically induced contractions were blocked by tetrodotoxin and alpha-adrenoceptor blockade. They were abolished in calcium-deficient medium, and suppressed by the calcium channel blockers in the order of potency nifedipine greater than verapamil greater than diltiazem. The maximum blocking effect of nifedipine was approximately 40%. All the blockers practically abolished K+-induced contractions. It is concluded that even if the contractile response of the human vas deferens to electrical stimulation is dependent on extracellular calcium, calcium channel blockers seem to have only a limited effect on this contraction and their capability of impairing the function of the vas deferens in patients is questioned.     

Effects of arginase inhibitors on the contractile and relaxant responses of isolated human penile erectile tissue

Objectives  

An impairment in the local availability of nitric oxide (NO) may impair male erectile function. The activity of l-arginine-degrading arginase enzymes may attenuate the relaxation of cavernous smooth muscle by reducing local NO production. Arginase enzymes compete with the nitric oxide synthases for the common substrate, the amino acid l-arginine. Very little data are available regarding the significance of arginase enzymes in the control of human penile erectile tissue. The aim of the present study was to elucidate the effects of drugs known to inhibit arginase activity on the relaxation of isolated human corpus cavernosum (HCC) and the production of cyclic GMP.     

Succinylcholine potentiates acetylcholine-induced contractile and phosphatidylinositol responses of rat trachea

Purpose Although succinylcholine (SCh) is often used as a muscle relaxant in electroconvulsive therapy, its influence on airway reactivity has not been fully investigated. We examined the effects of SCh on acetylcholine (ACh)-, carbachol (CCh)-, and electrical field stimulation (EFS)-induced contractions, and on the ACh-induced phosphatidylinositol (PI) response of rat trachea. Methods Thirty-two male Wistar rats weighing 250–350 g were used. The trachea was rapidly isolated and cut into 3-mm-wide rings. The resting tension was adjusted periodically to 1.0 g during the equilibration period. ACh, 1 μM; carbachol (CCh), 0.05 μM; or neither of them, was added, and SCh was then added at 1–300 μM final concentrations, and ring tension was examined. Contractions were elicited by EFS in the presence or absence of 100 μM SCh. Tracheal slices were incubated with [³H] myo-inositol, 1 μM ACh, and various concentrations of SCh. The accumulation of [³H] inositol monophosphate (IP₁) was measured. Results SCh did not affect the tension by itself without ACh, or with CCh, but SCh potentiated the ACh-induced contraction of rat trachea at concentrations of 10 μM or more (50% effective concentration [EC₅₀]; 43.6 μM). SCh produced a significant increase in the amplitude and duration of EFS-induced contractions. SCh, at concentrations of 10 μM and 100 μM, potentiated ACh-induced IP₁ accumulation. Conclusion SCh potentiated ACh-induced, but not CCh-induced, contractile and PI responses, and enhanced EFS-induced contraction of rat trachea, suggesting that competition for butyrylcholinesterase (BChE) in airway smooth muscle could be involved in the potentiation by SCh of ACh-induced airway smooth muscle contraction.     

Effects of vasopressors on contractile and phosphatidylinositol responses of rat trachea

Purpose. Vasopressors, such as dopamine (DA), norepinephrine (NE), and phenylephrine (Phe), are commonly used during anesthesia to increase blood pressure through α₁-adrenoceptors. The present study was designed to examine the effects of DA, NE, and Phe on the contractile and phosphatidylinositol (PI) responses of the rat trachea induced by a muscarinic agonist, carbachol (CCh). Methods. A rat tracheal ring was suspended between two stainless-steel hooks in Krebs-Henseleit (K-H) solution. Contraction was induced with 0.55 μM CCh, and 30 min later DA, NE, or Phe was added. The tracheal slices were incubated in K-H solution containing LiCl, ³[H]myo-inositol, and CCh in the presence or absence of DA, NE, or Phe. The ³[H]inositol monophosphate (IP₁) formed was measured. Results. CCh caused tracheal ring contraction. NE attenuated CCh-induced contraction at a dose of 1 μM or greater and had a maximal effect at 3 μM. DA and Phe did not affect CCh-induced contraction. CCh-induced IP₁ accumulation was potentiated significantly by NE and Phe, but not by DA. Conclusion. Although NE and Phe potentiated CCh-induced IP₁ accumulation, they could not potentiate CCh-induced contraction, suggesting that in clinical settings, vasopressors such as NE, DA, and Phe might be safely used in patients with asthma. Received: February 25, 2002 / Accepted: July 2, 2002 Acknowledgments. This study was supported in part by a Grant-in-Aid for Scientific Research C (no. 10671421), from the Ministry of Education, Science, and Culture, Japan. Address correspondence to: O. Shibata     

Effects of ketamine on neostigmine-induced contractile and phosphatidylinositol responses of the rat trachea

Purpose. Neostigmine causes airway smooth muscle contraction through the direct stimulation of muscarinic receptors and the activation of phosphatidylinositol (PI) responses. Ketamine attenuates airway smooth muscle contraction. It is not clear whether ketamine attenuates neostigmine-induced airway smooth muscle contraction by inhibiting the PI response. This study was designed to examine the effects of ketamine on neostigmine-induced contractile and PI responses of the rat trachea. Methods. Thirty male Wistar rats weighing 250–350 g were used. In the experiment on the contractile response, active contraction was induced with 1 μM neostigmine in the presence or absence of ketamine. In the experiment on the phosphatidylinositol response, the trachea slices were incubated with [³H]myo-inositol, 1 μM neostigmine, or 100 μM aluminum fluoride, and ketamine. The formation of [³H]inositol monophosphate (IP₁), a degradation product of the phosphatidylinositol response, was measured with a liquid scintillation counter. Statistical significance (P < 0.05) was determined by analysis of variance. Results. Neostigmine 1 μM caused tracheal ring contraction. This contraction was attenuated by ketamine dose-dependently and reached resting tension at 100 μM. Neostigmine- and aluminum fluoride-induced IP₁ accumulation was also attenuated by ketamine. Conclusion. The results suggest that ketamine attenuates neostigmine-induced contractile responses, at least in part, through the inhibition of phospholipase C coupled with G protein in the PI response. Received: December 12, 2002 / Accepted: February 8, 2003 Acknowledgments. This study was supported in part by Grant-in-Aid for Scientific Research C, No. 10671421, from the Ministry of Education, Culture, Sports, Science, and Technology, Japan. Address correspondence to: M. Saito     

Reduction of postischemic contractile dysfunction of the isolated rat heart by sevoflurane: comparison with halothane

Our aims were to evaluate the effect of sevoflurane on postcardioplegic functional recovery of the isolated rat heart including the role of the adenosine triphosphate regulated potassium (K(ATP)) channels and to compare the cardioprotective effects of equipotent concentrations of halothane and sevoflurane. Isolated perfused rat hearts were subjected to 45 or 60 min normothermic cardioplegic arrest and 30 min reperfusion. Sevoflurane (0.9% and 1. 7%), halothane (0.4% and 0.8%), or sevoflurane (0.9%) plus glibenclamide (10 microM) (a K(ATP) channel blocker) were administered at different time intervals. Measurements of mechanical activity were made before and after arrest. Function during reperfusion after cardioplegic arrest was significantly depressed in both untreated and treated hearts. However, sevoflurane administered both before and after arrest, or before only, significantly improved functional recovery after 45 min of cardioplegia. This protective effect was abolished by simultaneous administration of glibenclamide, suggesting a role of the K(ATP) channel. Sevoflurane was as effective as halothane in improving postcardioplegic functional performance. After 45 min of arrest, hearts exposed to either anesthetic at both concentrations had a significantly higher work performance on discontinuation of their administration than untreated controls. After 60 min of arrest, neither anesthetic elicited protection.     

Inhibition by AICA riboside of gluconeogenesis in isolated rat hepatocytes.

5-Amino-4-imidazolecarboxamide (AICA) riboside, the nucleoside corresponding to AICA ribotide (AICAR or ZMP), an intermediate of the de novo pathway of purine biosynthesis, was found to exert a dose-dependent inhibition on gluconeogenesis in isolated rat hepatocytes. Production of glucose from lactate-pyruvate mixtures was half-maximally inhibited by approximately 100 microM and completely suppressed by 500 microM AICA riboside. AICA riboside also inhibited the production of glucose from all other gluconeogenic precursors investigated, i.e., fructose, dihydroxyacetone, and L-proline. Measurements of intermediates of the glycolytic-gluconeogenic pathway showed that AICA riboside provoked elevations of triose phosphates and fructose-1,6-bisphosphate and decreases in fructose-6-phosphate and glucose-6-phosphate. The effects of AICA riboside persisted when the cells were washed 10 min after its addition but were suppressed by 5-iodotubercidin, an inhibitor of adenosine kinase. AICA riboside provoked a dose-dependent buildup of normally undetectable Z nucleotides. After 20 min of incubation with 500 microM AICA riboside, ZMP, ZTP, and ZDP reached 3, 0.3, and 0.1 mumol/g cells, respectively. Concentrations of ATP were not significantly modified by addition of up to 500 microM AICA riboside when the cells were incubated with lactate-pyruvate but decreased with fructose or dihydroxyacetone. The activity of rat liver fructose-1,6-bisphosphatase was inhibited by ZMP with an apparent Ki of 370 microM. It is concluded that AICA riboside exerts a suppressive effect on gluconeogenesis because it provokes an accumulation of ZMP, which inhibits fructose-1,6-bisphosphatase.(ABSTRACT TRUNCATED AT 250 WORDS)     

The contractile responses of isolated dog cerebral and extracerebral arteries to oxybarbiturates and thiobarbiturates

In helical strips of dog cerebral, coronary, mesenteric, renal, and femoral arteries, the addition of thiamylal and thiopental, 10(-5) to 10(-3) M, caused a dose-related contraction; the contraction was significantly more intense in cerebral than in extracerebral arteries. Secobarbital caused a slight contraction only in the cerebral artery. In contrast, pentobarbital did not produce a contraction in any artery studied. The thiamylal-induced contraction was not affected by treatment with phentolamine, diphenhydramine, or cinanserin but was attenuated by treatment with Ca entry blockers, such as nifedipine or diltiazem. In the cerebral artery soaked in Ca++-free media for 60 min, the addition of Ca++ produced triphasic responses; a transient contraction followed by a relaxation and a slowly developing, persistent contraction. The persistent contraction was potentiated by 10(-4) M thiamylal but abolished at 10(-3) M. In the mesenteric artery soaked in Ca++-free media, the addition of Ca++ produced only a slight contraction, which was potentiated by thiamylal (10(-4) and 10(-3) M). It is concluded that thiobarbiturates are more potent vasoconstrictors than oxybarbiturates and that the barbiturates produce greater contraction in cerebral arteries than in extracerebral arteries. The thiamylal-induced contraction appears to be associated mainly with influx of Ca++ from extracellular fluids.     

Polyamines antagonizing angiotensin II contractile effects in isolated rat aorta

Our study showed that the administration in pre-treatment of some polyamines (especially spermine and spermidine and almost null agmatine, putrescine and cadaverine) reduced the contractile effects of angiotensin II (Ang II) in isolated rat aorta. These effects might not be associated to the interference of clathrin coated vesicles (coated pits) formation or caveolae interaction (and thus to Ang II internalization through AT1 receptors). In contrast, these effects seem to be due to the interaction with voltage-gated membrane Ca2+ channels. Therefore, the alteration of transmembrane Ca2+ fluxes does not exclude the involvement of internalization process through coated pits or caveolae, since the endocytosis mediated by these phenomena essentially needs Ca2+. In addition, the inhibitory effects are dependent on the number of positive charges of the polyamine molecules.     

Cytoskeletal and contractile proteins in detrusor smooth muscle from bladders with outlet obstruction--a comparative study in rat and man.

Detrusor biopsies were obtained from patients with urinary outlet obstruction due to prostatic enlargement and from age-matched control patients. The relative amounts of actin and myosin and their isoforms, as well as desmin and filamin were determined and compared with corresponding results from bladders from control rats and rats with 10 days of experimental outlet obstruction of the urinary bladder. In the human control detrusor the actin/myosin ratio was similar to that in the control rat. The isoform distribution of the myosin heavy chains differed between man and rat. In the biopsies from the patients with outlet obstruction and in the obstructed rat bladders the actin/myosin ratio was increased. A change in the myosin heavy chain distribution in the obstructed bladders was observed for both species. The filamin/actin ratio increased significantly in the obstructed rat bladders and tended to increase in the obstructed human bladders. Desmin was the dominating intermediate filament protein. The desmin/actin ratio increased in obstructed bladders in man and in rat.     

Autonomous contractile activity in the isolated rat bladder is modulated by a TRPV1 dependent mechanism

AIMS: Resiniferatoxin (RTX), a vanilloid compound and agonist of the transient receptor potential channel 1 (TRPV1), is known for its beneficial effects on neurogenic detrusor overactivity. The mainstream rationale for its use is the desensitization of TRPV1 on sensory bladder afferents. However, recent findings showed that TRPV1 is present in other cell types in the bladder. To eliminate the effects of RTX on spinal and central neural circuits, we investigated autonomous contractility in normal and neurogenic rat bladders after treatment with RTX. METHODS: Female Wistar rats were made paraplegic at vertebral level T8-T9. Animals were intravesically pre-treated with vehicle (ethanol 5%) or RTX (100 nM) and sacrificed after 72 hr. Each bladder was excised and placed in a heated organ bath, where intravesical pressures were measured. Effects on contractile parameters of intravesical volume load, the non-selective muscarinic receptor agonist carbachol (CA) and electrical stimulation (ES) of nerves were studied in both groups. RESULTS: In RTX-treated normal bladders we found shorter contractions with higher amplitude than in control bladders (P < 0.05). In RTX-treated neurogenic bladders the amplitude and duration of autonomous contractions were increased compared with controls (P < 0.05). Furthermore RTX induced an increased response to CA and to ES (P < 0.05). CONCLUSIONS: RTX significantly affected the properties of autonomous bladder contractile activity. This provides evidence for local effects of RTX on bladder contractile activity, which are not mediated by afferent neural pathways and which may contribute to the beneficial effects on detrusor overactivity. TRPV1 and TRPV1(+) cells seem to play an important role in (autonomous) bladder contractility.     

心脏瓣膜间质成纤维细胞收缩功能的研究

目的 研究人心脏瓣膜间质成纤维细胞的收缩性能，探讨其在瓣膜病理形态发生中的作用。方法 将人正常二尖瓣（５枚）及手术切除的风湿性二尖瓣（１０枚）组织来源的瓣膜间质成纤维细胞在胶原凝胶系统中培养，观察体外培养６、１２ｈ和１周成纤维细胞的形态学特征及其凝胶直径的缩小情况。结果 正常及病变二尖瓣组织来源的成纤维细胞在胶原凝胶中的形态改变差异无显著性，在胶原凝胶内呈长梭形。培养１周后，风湿性二尖瓣组织成纤维     

Influence of halothane and isoflurane on the contractile responses to potassium and prostaglandin F2{alpha} in isolated human pial arteries

Volatile anaesthetics may modulate cerebrovascular resistance,but their direct actions on human cerebral arteries are unknown.In the present study, we have evaluated the effects of halothaneand isoflurane at different MAC (0.4, 1.0 and 2.0) on contractionsinduced by depolarization (potassium) or receptor stimulation(prostaglandin F₂) in isolated ring segments of human pial arteries.Neither halothane nor isoflurane had significant effects onpotency (unaffected EC₅₀ value) or the maximum response (Emax)in potassium-contracted arteries, even though there was a generaltendency to attenuation of Emax. Similarly, the potency of prostaglandinF₂ was unchanged (unaffected EC₅₀ value). However, the Emaxvalue for prostaglandin F₂ at normocapnia (mean Pco₂ 4.3 (SEM0.1) kPa, pH 7.41 (0.01)) and addition of halothane (0.4, 1.0and 2.0 MAC) was significantly attenuated to 96 (2) %, 91 (3)%and 84 (4) % at the respective MAC concentrations. Isofluraneat 2 MAC and normocapnia also reduced Emax to 94 (3) %. Duringhypocapnia (Pco₂ 2.7 (0.1) kPa, pH7.64 (0.01)), the vasodilatoreffect of halothane was reduced, whereas isoflurane at 0.4 and1.0 MAC enhanced the contraction induced by prostaglandin F₂.(Br. J. Anaesth. 1994; 72: 581–586)     

Isoflurane and sevoflurane precondition against neutrophil-induced contractile dysfunction in isolated rat hearts

BACKGROUND: The authors tested the hypothesis that pretreatment with isoflurane or sevoflurane can protect the heart against neutrophil-induced contractile dysfunction. METHODS: Studies were conducted in buffer-perfused and paced isolated rat hearts. Left ventricular developed pressure served as an index of contractility. Pretreatment consisted of administration of 1.0 minimum alveolar concentration isoflurane or sevoflurane for 15 min followed by a 10-min washout and was performed in the absence and presence of the adenosine triphosphate-sensitive potassium channel inhibitor glibenclamide (10 microM). Polymorphonuclear neutrophils and platelet-activating factor were then added to the perfusate for 10 min, followed by 30 min of recovery. Neutrophil retention was assessed from the difference between those administered and collected in coronary effluent and measurements of myeloperoxidase in myocardial samples. Isolated hearts were also used to assess the effect of volatile anesthetic pretreatment on cardiac dysfunction caused by enzymatically generated superoxide. In additional studies, the authors evaluated the effect of volatile anesthetic pretreatment on the adherence of neutrophils to isolated rat aortic segments. RESULTS: Platelet-activating factor-stimulated neutrophils caused marked and persistent reductions (> 50%) in left ventricular developed pressure. Pretreatment with either isoflurane or sevoflurane abolished these effects, as well as the associated increases in neutrophil retention. Glibenclamide did not alter these actions of the anesthetics. Pretreatment with either volatile anesthetic attenuated the reductions in left ventricular developed pressure caused by exogenous superoxide and abolished the increases in neutrophil adherence in the aortic segments. CONCLUSION: Isoflurane and sevoflurane preconditioned the heart against neutrophil-induced contractile dysfunction. This action was associated with an inhibition to neutrophil adherence and likely involved an increased resistance of the myocardium to oxidant-induced injury; the adenosine triphosphate-sensitive potassium channels played no apparent role.     

Alterations in purinergic and cholinergic components of contractile responses of isolated detrusor contraction in a rat model of partial bladder outlet obstruction

OBJECTIVE: To study the effect of 3 weeks of partial bladder outlet obstruction (BOO), compared to a sham operation, on the cholinergic and purinergic components of detrusor contractile responses to agonists and to electrical field stimulation (EFS); the expression of P2X receptor subtypes was also examined. MATERIALS AND METHODS: Partial BOO was induced in female Sprague-Dawley rats by surgically applying a jeweller's silver 'jump' ring around the urethra, such that the urethra was constricted but not closed. Sham-operated female rats underwent an identical procedure without placement of a ring. RESULTS: After 3 weeks of partial BOO the rat bladders became significantly hypertrophied, doubling in weight. Spontaneous activity was markedly increased, but the contractile response to a single bolus of KCl (120 mM) was unaltered. The neurogenic-induced contractile responses of strips of detrusor from obstructed bladders were significantly greater than those from sham-operated bladders, and the responses of strips of detrusor from obstructed bladders to EFS showed a significantly greater atropine-sensitive component than sham-operated detrusor. However, the response of detrusor strips to EFS that was susceptible to desensitization by alpha,beta-methylene ATP was not significantly changed in obstructed bladders. The sensitivity of the strips from obstructed bladders to carbachol, ATP and beta,gamma-methylene ATP was less than in sham-operated detrusor. Immunohistochemical studies showed no difference in the P2X receptor subtypes expressed on detrusor smooth muscle from obstructed and sham-operated rats. CONCLUSION: In the rat, after moderate bladder hypertrophy, the atropine-sensitive component was significantly up-regulated, but the ATP-sensitive component was marginally reduced, although not significantly. These results suggest that up-regulation of the P2X component of bladder contraction seen in humans with bladder instability, and in other species models of BOO, is not mirrored in the rat, or occurs later in the pathological process of bladder hypertrophy.     

Inhibition of glucose uptake by 5-hydroxyindoleacetic acid in the isolated rat soleus muscle

Accumulated end-products were identified to participate in the late development of glucose intolerance and insulin resistance (IR) in patients with chronic renal insufficiency. The possible pathophysiological role of accumulated 5-hydroxyindoleacetic acid (5HIAA) in the genesis of IR was investigated employing anin vitro animal model. 5HIAA inhibited the basal glucose uptake in isolated rat soleus muscle with intact membrane with A₅₀=1.25 μmol/l, and E_max=88.6%. 5HIAA significantly inhibited the insulin, and tolbutamide stimulated glucose uptake. In Ca and Mg depletion 5HIAA showed a partially additive inhibitory effect, while nonadditive inhibitory activity was observed in the case of K⁺ excess. It is concluded that 5HIAA is a metabolically active end-product interfering with glucose uptake in muscle at an insulin postreceptor level, and its effect is related to Ca modulation in the insulin regulatory cascade.