Reduction In Maximum Response Research Articles

Chronic Unpredictable Stress Impairs Vascular Reactivity in Male and Female Mice

Background: Chronic stress is known to induce vascular inflammation causing endothelial and vascular smooth muscle dysfunction. Changes in the hypothalamic-pituitary-adrenal axis lead to increased sympathetic and decreased parasympathetic drive, causing the release of inflammatory cytokines in the vasculature, by mechanisms that are unclear. Hypothesis: We hypothesize that chronic unpredictable stress (CUS) increases reactive oxygen species and induces gasdermin pore formation and voltage-dependent anion channel (VDAC) oligomerization in the membrane of the mitochondria, which releases mitochondrial DNA (mtDNA) to the cytosol and induces TNF-α, IL-1β and IL-18 production through activation of the NLRP-3 inflammasome pathway. Methods: Adult male and female C57Bl6/J mice were exposed to 28 consecutive days of chronic unpredictable stress (CUS) or handling (CTL). Systolic blood pressure (SBP) was measured at the end of the stress period by tail cuff plethysmography. Vascular function using myographs was assessed on isolated mesenteric resistance arteries (MRAs), pudendal artery (PA) and aorta from male and female CUS and CTL mice. The arterial rings were kept in physiological salt solution at 37°C, constantly aerated with 95%O2/5%CO2. Concentration-response curves to phenylephrine (PE; 1nM-30μM) and acetylcholine (ACh; 1nM-30μM) were performed. Expression of gasderminD was measured in the MRA by western blot. Concentration-response curves were analyzed using non-linear regression analysis. Data are presented as mean ± S.E.M. Statistical significance set at p<0.05. Data were analyzed with GraphPad Prism 9.2.0. Results: SBP was increased by 12.1±4.9% in CUS mice. In CUS mice, compared to the CTL, the potency of ACh-induced relaxation was decreased in the MRA (pEC50 CUS 6.17±0.09 vs CTL 6.81±0.11; p=0.003) and PA (pEC50 CUS 6.65±0.07 vs CTL 6.31±0.09; p=0.008) but not in the aorta of male mice. In females, the potency to ACh was decreased only in the MRA (pEC50 CUS 5.94±0.30 vs CTL 6.98±0.15; p=0.041). There were no differences in the contractile responses to PE between controls and mice exposed to CUS in the MRA and PA of both males and females, while in the aorta of CUS males, there was a significant reduction in maximal response (EMAX CTL: 4.70±0.48 mN vs CUS 3.01± 0.23mN; p=0.007). The expression of gasderminD was increased in MRA of female mice only. Conclusion: Our results show that, in both sexes, CUS increased SBP and induced vascular dysfunction observed by impaired reactivity to ACh and PE, with increased expression of gasderminD in MRA of female mice only. These results suggest that the vascular adaptations to CUS are sex-dependent. This work was supported by NIH grants P20GM109091 (F.H.), R01HL130972-01A1 (F.G.S.), R01HL5949 (F.G.S.), RO1DK132948 (C.W. & F.P.) and R01 MH129798 (SKW); VA grants: VISN7 RDA (F.H.), Merit awards: BX000168-10A1 (F.G.S.), BX005320 (F.G.S.), and BX002604 (M.J.R.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the abstract. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Suppression of top-down influence decreases neuronal excitability and contrast sensitivity in the V1 cortex of cat

How top-down influence affects neuronal activity and information encoding in the primary visual cortex (V1) remains elusive. This study examined changes of neuronal excitability and contrast sensitivity in cat V1 cortex after top-down influence of area 7 (A7) was modulated by transcranial direct current stimulation (tDCS). The neuronal excitability in V1 cortex was evaluated by visually evoked field potentials (VEPs), and contrast sensitivity (CS) was assessed by the inverse of threshold contrast of neurons in response to visual stimuli at different performance accuracy. We found that the amplitude of VEPs in V1 cortex lowered after top-down influence suppression with cathode-tDCS in A7, whereas VEPs in V1 did not change after sham-tDCS in A7 and nonvisual cortical area 5 (A5) or cathode-tDCS in A5 and lesioned A7. Moreover, the mean CS of V1 neurons decreased after cathode-tDCS but not sham-tDCS in A7, which could recover after tDCS effect vanished. Comparisons of neuronal contrast-response functions showed that cathode-tDCS increased the stimulus contrast required to generate the half-maximum response, with a weakly-correlated reduction in maximum response but not baseline response. Therefore, top-down influence of A7 enhanced neuronal excitability in V1 cortex and improved neuronal contrast sensitivity by both contrast gain and response gain.

Antihypertensive potential of selected pyrimidine derivatives: Explanation of underlying mechanistic pathways

This study was designed to determine the effectiveness of 5-(3-Hydroxybenzylidene)-2, 4, 6(1H, 3H, 5H)-pyrimidinetrione (SR-5), 5-(4-Hydroxybenzylidene)-2, 4, 6(1H, 3H, 5H)-pyrimidinetrione (SR-8), 5-(3-Chlorobenzylidene)-2, 4, 6(1H, 3H, 5H)-pyrimidinetrione (SR-9) and 5-(4-Chlorobenzylidene)-2, 4, 6(1H, 3H, 5H)-pyrimidinetrione (SR-10) against hypertension. In deoxycorticosterone acetate-salt rats, SR-5, SR-8, SR-9, and SR-10 reduced blood pressure and normalized renal functions. In isolated rat aortic rings, SR-5, SR-8, SR-9, and SR-10 relaxed phenylephrine (PE) and K+-induced contractions. The vasodilator effect was endothelium-independent. Test compounds caused a rightward shift of Ca++ and PE concentration-response curves with a reduction of maximum response. SR-5, SR-8, SR-9, and SR-10 inhibited PE peak contractions in a Ca++ free medium. In guinea-pig atria, SR5, SR-8, SR-9, and SR-10 caused a mild-to-moderate inhibition of force and rate of contractions. In the aorta and heart tissues, the test compounds enhanced glutathione-s-transferase, reduced glutathione and catalase levels, improved cellular architecture, and decreased lipid peroxidation and expression of inflammatory markers: cyclooxygenase 2, tumor necrosis factor alpha, phosphorylated c-Jun N-terminal kinase, and phosphorylated-nuclear factor kappa B, evidenced in the immunohistochemistry, enzyme-linked immunosorbent assay, western blot molecular investigations and a decreased mRNA expression of calcium channel in RT-PCR analysis. SR-5, SR-8, SR-9, and SR-10 increased the urinary output in rats and inhibited the human platelet aggregation. This study revealed that SR-5, SR-8, SR-9, and SR-10 possess BP lowering, reno-protective, vasodilatory (mediated via Ca++ antagonist, antioxidant and anti-inflammatory pathways), partial cardio-suppressant, diuretic, and antiplatelet effects, demonstrating their therapeutic potential in hypertension management.

The influence of low level laser irradiation on vascular reactivity

PurposeThe mechanism of action of low level laser irradiation on tissues is unclear. Authors of publications present the positive clinical impact of low and medium power laser irradiation on vascular reactivity. The purpose of this study was to analyze the role of vascular endothelium in laser-induced constricted by endothelin-1 and phenylephrine. Materials and methodsExperiments were performed on isolated and perfused rat tail arteries of weighing 250–350g male Wistar rats. Contractility of arteries as a response to endothelin-1 and phenylephrine was measured after exposure to laser stimulation (10, 30 and 110mW). ResultsLaser irradiation inhibits vascular smooth muscle contraction induced by endothelin-1 and an alpha-adrenergic receptor agonist, phenylephrine proportionally to the laser power. Concentration-response curves were shifted to the right with significant reduction in maximal response. Laser irradiation at the power of 10mW, 30mW, and 110mW reduced the maximum response of arteries stimulated with phenylephrine sequentially to 88%, 72%, and 52%. Similar findings were observed during stimulation of endothelin-1. Laser irradiation at the power of 10mW, 30mW and 110mW resulted in maximal response respectively reduced to 94%, 62% and 38%. ConclusionOur results strongly suggest that during low level laser irradiation vascular smooth muscle cells reactivity is reduced, this effect is present in arteries with normal endothelium. The mechanism of action of laser biosimulation on tissues is unclear. Authors of publications present the positive clinical impact of low level laser irradiation on vascular reactivity.

Physical training promotes similar effects to the blockade of angiotensin-converting enzyme on the cardiac morphology and function in old female rats subjected to premature ovarian failure.

We investigated the effects of angiotensin-converting enzyme (ACE) inhibition and aerobic physical training on the heart of old female rats (82-wk-old) submitted to premature ovarian failure (10-wk.-old). We used different approaches: morphology and function by echocardiography, reactivity of the coronary bed and left ventricular contractibility (Langendorff Technique). Female Wistar ovariectomized (OVX) rats (n=42) were assigned to one of four groups: OVX, vehicle treated only; OVX-EM, Enalapril Maleate only (EM, 10mg·kg-1·d-1); OVX-T, aerobic trained only; and OVX-EMT, treated with Enalapril Maleate and aerobic trained. Both Enalapril Maleate treatment and aerobic training were done in the last 20weeks of the experimental protocol. When compared to the OVX group, the OVX-EM group showed lower values of wall thickness and left ventricular (LV) mass, lower values of coronary bed reactivity and reduced maximum response of LV contractility to dobutamine, while the OVX-T group showed lower values of LV wall thickness, increase in end-systolic volume, reduced maximum response of LV contractility to dobutamine, and left intraventricular pressure due to increased flow. The combination of treatments (EM and aerobic physical training) did not promote additional important effects on the parameters evaluated. Our results suggest similar beneficial effects of physical training and EM treatment on the morphology and cardiac function in old female rats submitted to premature ovarian failure. Although the causes of these benefits are still unknown, both treatments have promoted a decrease in cardiac contractility, and the reduced β1-adrenergic sensitivity suggests that both treatments may attenuate the sympathetic effect on the heart.

Modulatory effect of sodium nitroprusside and 8Br-cGMP on mastoparan-7 induced contraction

I n t r o d u c t i o n . Mastoparan-7 activates G-protein and stimulates apoptosis, but in smooth muscle cells leads to increase in perfusion pressure. Main a i m of this study was to evaluate the modulatory effect of 8Br-cGMP and sodium nitroprusside on vascular smooth muscle contraction induced by direct stimulation of G-protein with mastoparan-7. Ma t e r i a l a n d m e t h o d s . Experiments were performed on isolated and perfused tail artery of Wistar rats. Contraction force in our model was measured by increased level of perfusion pressure with a constant flow. R e s u l t s . Concentration-response curves obtained for mastoparan-7 presented an sigmoidal relation. In presence of SNP and 8Br-cGMP the significant and dose dependent leftward shift with significant reduction in maximal responses was present. Moreover, analyzing function of calcium stores the significant inhibition of influx from both, intra- and extracellular calcium stores was present. C o n c l u s i o n . Results of our experiments suggest that contraction induced by direct activation of G-protein with mastoparan-7 may by effectively inhibited in the presence of donors of nitric oxide such as sodium nitroprusside and in the presence of 8Br-cGMP.

Effect of pertussis toxin on calcium influx in three contraction models

Pertussis toxin (PTX) blocks G protein activation and inhibits signal transmission from the activated receptor to effectors that are specific for the G protein-coupled receptor. The aim of the present study was to evaluate the effect of PTX on vascular smooth muscle cells that were stimulated pharmacologically with phenylephrine (α-adrenoceptor agonist), mastoparan-7 (direct G-protein activator) and Bay K8644 (direct calcium channel activator). The changes in perfusion pressure that were proportional to the degree of phenylephrine-induced constriction of rat tail arteries were assessed. Concentration-response curves (CRCs) that were obtained for phenylephrine, mastoparan-7 and Bay K8644 presented a sigmoidal association. A significantly reduced calcium influx to the cytoplasm in the presence of mastoparan-7 resulted in a significant rightward shift of the CRCs with a significant reduction in maximal responses. The presence of PTX did not change mastoparan-7 and Bay K8644-induced contraction, whereas the significant inhibition of phenylephrine-induced contraction was found. The results of the experiments indicated that PTX significantly inhibited phenylephrine-induced contraction of vascular smooth muscle cells by inhibition of calcium influx from the intra- and extracellular calcium space. PTX did not change the smooth muscle contraction that was induced by mastoparan-7 and Bay K8644. The predominant effect of mastoparan-7 may be associated with other binding sites as compared to the G-protein or PTX may bind to other sites than mastoparan-7.

Direct regulation of vascular smooth muscle contraction by mastoparan-7

Mastoparan-7 (mas-7) is a basic tetradecapeptide isolated from wasp venom, which activates guanine nucleotide-binding regulatory proteins (G-proteins) and stimulates apoptosis. In smooth muscle cells, mas-7 leads to an increase in the perfusion pressure. The main aim of this study was to evaluate the physiological effect of the direct stimulation of G-proteins in comparison to the typical stimulation of receptors in vascular smooth muscle cells (VSMCs). Experiments were performed on the isolated and perfused tail artery of Wistar rats. The contraction force in our model was measured by an increased level of perfusion pressure with a constant flow. The concentration response curves (CRCs) obtained for mas-7 were sigmoidal. In comparison to the curves for phenylephrine and vasopressin, the mas-7 curve was significantly shifted to the right with a significant reduction in maximal response. Mas-7 significantly increased the perfusion pressure for the intra- and extracellular calcium (Ca2+) influx to the cytoplasm. The presence of the pertussis toxin (PT) did not affect the mas-7-induced contraction. In comparison to phenylephrine and vasopressin, all the values of perfusion pressure following stimulation of the G-proteins by mas-7 were significantly lower. The results of our experiments suggested that mas-7 significantly induces the contraction of VSMCs. The binding site for mas-7 is different from that for PT; thus, PT does not affect VSMC contraction. The tissue effect of this stimulation is comparable to the stimulatory effect of partial agonists. Current knowledge regarding the apoptosis pathway reveals the significance of Ca2+ ions involved in this process. Therefore, mas-7 may induce apoptosis through an increase in the cytoplasmic Ca2+ concentration; however, the use of this mechanism in anticancer therapy must be preceded by a molecule modification that eliminates the vasoconstrictive effect.

207306 摩擦特性による吸収エネルギと最大応答の低減(一般02 機械力学・制御工学10)

207306 摩擦特性による吸収エネルギと最大応答の低減(一般02 機械力学・制御工学10)

Histological, biochemical and pharmacologycal characterization of the gastric muscular layer in Chagas disease

To assess in vitro the correlation between the number of neurons and the sensitivity to cholinergic drugs and acetylcholinesterase activity in chagasic patients. A 3 x 1 cm strip of the muscle layer of the anterior part of the stomach, always close to the angular incisure, was removed from 10 chronic chagasic patients (6 men) submitted to megaesophagus or megacolon surgery and from 10 non-chagasic patients (4 men) submitted to other types of surgery (control group), aged on average 52.3 and 50.1 years, respectively, for histological and pharmacological studies. The action of cholinergic drugs was investigated in isolated preparations according to the superfusion method of Ferreira and Costa, and acetylcholinesterase activity was determined by the method of Ellman. For neuron count, the strips were cut into 8 µm sections according to the method standardized by Alcântara. There was a difference in number of neurons between the chagasic (5,6) and control (7,3) groups. Acetylcholinesterase activity, in moles of hydrolyzed substrate per minute per gram tissue, was reduced in chagasic patients (4,32) compared to the controls (7,30). No hypersensitivity of the gastric musculature to cholinergic drugs was detected, with a reduced maximum response to carbachol and betanechol in the chagasic group. The reduction of neurons in the myenteric plexus of the stomach of chronic chagasic patients can be demonstrated even in the absence of clinical chagasic gastropathy. The hypersensitivity of the gastric musculature to cholinergic drugs probably depends on intense denervation. The reduced acetylcholinesterase activity demonstrates the involvement of the cholinergic innervation in the stomach of chronic chagasic patients. There was no correlation between number of neurons, sensitivity to cholinergic drugs and acetylcholinesterase activity in the gastric musculature of chagasic and non-chagasic patients.

Bronchodilatory effect of Acorus calamus (Linn.) is mediated through multiple pathways

Aim of the study This study was undertaken to provide a pharmacological basis for traditional use of Acorus calamus in airways disorders. Materials and methods Isolated guinea-pig trachea and atria were suspended in organ baths bubbled with carbogen and mechanisms were found using different parameters. Results In isolated guinea-pig tracheal segments, crude extract of Acorus calamus was more effective than carbachol in causing relaxation of high K + (80 mM) precontractions, similar to verapamil, suggesting blockade of calcium channels. The n-hexane fraction was equipotent against both precontractions, similar to papaverine, while ethylacetate fraction was more potent against carbachol precontractions but had a negligible dilator effect against K +, similar to atropine and or rolipram. Pretreatment of tracheal preparations with n-hexane or ethylacetate fractions potentiated isoprenaline-induced inhibitory concentration–response curves, similar to papaverine or rolipram. Pretreatment of tracheal preparations with ethylacetate fraction caused a rightward parallel shift in carbachol response curve at lower concentration (0.003 mg/mL) similar to atropine and a non-parallel shift at higher concentrations (0.01 mg/mL), with reduction of maximum response, similar to rolipram. In isolated guinea-pig atrial preparations, crude extracts, its fractions and papaverine inhibited force and rate of contractions at higher concentrations than the smooth muscle while verapamil was equipotent. Conclusion These data indicate the presence of unique combination of airways relaxant constituents in crude extract of Acorus calamus, a papaverine-like dual inhibitor of calcium channels and phosphodiesterase in n-hexane fraction and a novel combination of anticholinergic, rolipram-like phosphodiesterase4 inhibitor in ethylacetate fraction and associated cardiac depressant effect, provide a pharmacological basis for traditional use of Acorus calamus in disorders of airways.

Modulation of the Reaction of Vascular Smooth Muscle Cells to Angiotensin II Induced by Catalase and Aminotriasol During Ischemia–Reperfusion

Background We investigated the influence of catalase and aminotriasol on reactions of the smooth muscle cells induced by angiotensin II (ANG II) after ischemia–reperfusion (I/R). Materials and Methods Experiments were performed on perfused male Wistar rat tail arteries. Using classical pharmacometric methods we analyzed the influence of ANG II on vascular contraction, in the presence of catalase and aminotriazole, and after I/R. Results A reduction in maximal response and increased EC 5 value were observed after ischemia, while an increased maximal response and decrease EC 50 value were observed after reperfusion. Catalase decreased and aminotriasol increased maximal responses to ANG II. In the presence of catalase, reduction of the maximal response and increase in EC 50 value were observed after reperfusion. In the presence of aminotriasol, we observed increased maximal response and decreased EC 50 value after I/R. Conclusion Ischemia reduced and reperfusion increased the responses of vascular smooth muscle cells to ANG II. Catalase decreased and aminotriasol increased hyperreactivity of arteries to ANG II after reperfusion. These results suggested that antioxidative system modulates reactions induced by ANG II. Reperfusion impairs the balance between antioxidants and the production of reactive oxygen species.

Characteristics of tolerance in the guinea pig ileum produced by chronic in vivo exposure to opioid versus cannabinoid agonists

Few studies have compared the nature of tolerance that develops following chronic opioid treatment with that which develops after chronic cannabinoid exposure in the same tissue and species. The degree and character of tolerance induced by 7 twice daily injections of morphine or 5 daily injections of the cannabinoid receptor agonist, WIN-55,212-2, was examined by comparing the ability of DAMGO, 2-chloroadenosine (CADO) and WIN-55,212-2 to inhibit neurogenic contractions of the longitudinal muscle/myenteric plexus preparation (LM/MP) and the ability of nicotine to elicit contractions in the LM/MP. Chronic morphine treatment resulted in subsensitivity to all inhibitory agonists (rightward shift in IC 50 values of 4–5-fold) and an increased responsiveness to the excitatory effect of nicotine while chronic WIN-55,212-2 exposure resulted in subsensitivity only to WIN-55,212-2 and a reduction in maximum response to both WIN-55,212-2 and DAMGO but no change in responsiveness to CADO. Chronic WIN-55,212-2 treatment significantly reduced CB 1 but not MOR receptor protein abundance while chronic morphine treatment did not change either. Assessment of the distribution of MOR and CB 1 receptors in myenteric neurons revealed distinct individual receptor expression as well as co-localization which was unaffected by either cannabinoid or opioid treatment. Thus, in contrast to the heterologous tolerance that develops after opioid treatment, tolerance in the LM/MP following chronic in vivo WIN-55,212-2 exposure appears to be homologous in character and is accompanied by a selective decrease in CB 1 receptor protein abundance. The data suggest that the cellular basis of tolerance differs between the two systems.

Anti-ulcerogenic mechanisms of a lyophilized aqueous extract of Dalbergia monetaria L. in rats, mice and guinea-pigs.

The decoction of Dalbergia monetaria L. is popularly used in Brazil for the treatment of gastric ulcer and the lyophilized aqueous extract (LAE) of D. monetaria has significant anti-ulcerogenic activity and inhibits gastric ulcer lesions induced by pylorus-ligature, ethanol and hypothermic-restraint stress. This work was conducted to identify the antiulcerogenic mechanisms of action of the LAE of D. monetaria. We analysed the effect of the LAE on prostaglandin E2 (PGE2) synthesis and on the characteristics (pH, volume and total acid content) of gastric juice. The antagonism between the LAE and histamine or carbachol was also analysed. The LAE increased gastric mucosal PGE2 synthesis compared with control (89.7+/-21.5 and 52.6+/-11.8 pg mg(-1), respectively) as assayed by enzyme immunoassay in the rat stomach. The LAE reduced the total acid content of gastric juice, but did not modify pH or gastric volume significantly, in Shay rats. Dose-response curves to histamine were shifted to the right in guinea-pig isolated right atria (pD2 values were 5.77+/-0.2 and 5.42+/-0.3, respectively, in the absence and presence of the LAE), with a significant reduction in maximum response (140+/-15.1 and 98+/-13.0, respectively). The same effect was observed when the agonist was isoprenaline. The LAE had no effect on the dose-response curve to carbachol in rat fundus strips. Thus, the protective effect of the LAE on induced gastric lesions might be because of synergistic effects, e.g. increased PGE2 synthesis and antagonism of H2 histamine and beta-adrenergic receptors, reducing gastric acid secretion. Increased PGE2 synthesis results in increased protection, and antagonism of H2 histamine and beta-adrenergic receptors reduces aggressive factors against the gastric mucosa.

207 履歴復元力特性による吸収エネルギと最大応答の低減(振動低減・振動制御,OS-1 振動基礎,総合テーマ「伝統を,未来へ!」)

207 履歴復元力特性による吸収エネルギと最大応答の低減(振動低減・振動制御,OS-1 振動基礎,総合テーマ「伝統を,未来へ!」)

Expression and vasoconstrictor function of anorexigenic peptides neuromedin U-25 and S in the human cardiovascular system

Neuromedin U-25 (NMU-25), a brain-gut peptide with anorexigenic actions, was paired with the G-protein-coupled receptors NMU1 and NMU2 in 2000. NMU-25 elicited a potent hypertensive effect in rats but little is known about its cardiovascular effects in humans. We examined the hypothesis that NMU fulfils the criteria for controlling vascular reactivity within the human cardiovascular system. The radioligand [125I]-NMU-25 demonstrated specific, saturable, and high affinity (K(D) = 0.26 +/- 0.06 nM) binding in the human left ventricle and coronary artery, and quantitative reverse transcription-polymerase chain reaction revealed that mRNA encoding NMU1 predominated in these tissues. NMU-25-like immunoreactivity was detected in human plasma, left ventricle, coronary artery, saphenous vein, and epicardial adipose tissue, and both NMU-25 and a related peptide, neuromedin S (NMS), were identified by high-performance liquid chromatography in the left ventricle. NMU receptor and peptide were localized to endothelial cells, with the receptor also present on vascular smooth muscle cells. NMU-25 was a potent vasoconstrictor of isolated rings of human coronary and mammary artery and saphenous vein. Compared with NMU-25, NMS had a significantly reduced maximum response in saphenous vein, and the Arg165Trp variant of NMU-25, associated with childhood-onset obesity, was without effect. NMU-25 precursor mRNA was upregulated in the left ventricle from patients with dilated cardiomyopathy and ischaemic heart disease. We have detected the expression of both NMU receptor and peptide in human cardiovascular tissues and have shown that NMU-25 and NMS act as potent vasoconstrictors in human vascular beds.

PPARα and PPARβ Are Differentially Affected by Ethanol and the Ethanol Metabolite Acetaldehyde in the MCF-7 Breast Cancer Cell Line

The activity and/or the level of the peroxisome proliferator-activated receptors (PPARs) in liver and oligodendrocytes are regulated by ethanol. Despite the association between ethanol consumption and breast cancer risk, and the increasing evidence for an involvement of PPARs in some cancers, there have been no studies on the effect of ethanol or its metabolite acetaldehyde on PPARs in breast cancer. Using the MCF-7 breast cancer cell line, we examined the relationship between ethanol and its metabolite acetaldehyde on PPARalpha and PPARbeta transactivation. Ethanol (20 mM) reduced the potency of the PPARbeta ligand GW0742, evident by a rightward shift in the GW0742 dose-response curve, whereas for PPARalpha activation by GW7647, ethanol mediated its effects primarily through reducing efficacy as evidenced by a reduction in maximal response. Using the enzyme inhibitors 4-methylpyrazole and cyanamide and the metabolite acetaldehyde, we showed that PPARalpha and PPARbeta are differentially modulated by ethanol and acetaldehyde. While acetaldehyde is responsible for the inhibition of PPARalpha ligand inhibition with a concentration that inhibits 50% of activity (IC50) of 111 nM, acetaldehyde has no effect on PPARbeta or its ligand activation. Instead, inhibition of PPARbeta transactivation is mediated directly by ethanol. The differential effect of ethanol and acetaldehyde on PPARalpha and PPARbeta further underscores the differences between these receptors and may indicate the relevance of PPARs in the effects of ethanol in the human breast.

Altered responsiveness of the guinea‐pig isolated ileum to smooth muscle stimulants and to electrical stimulation after in situ ischemia

1. We evaluated changes in contractility of the guinea-pig isolated ileum, using intact segments and myenteric plexus-longitudinal muscle (MPLM) preparations, after several times (5-160 min) of ischemia in situ. 2. Intestinal ischemia was produced by clamping the superior mesenteric artery. Ischemic and nonischemic segments, obtained from the same guinea-pig, were mounted in organ baths containing Krebs-bicarbonate (K-B) solution, maintained at 37 degrees C and gassed with 95% O2/5% CO2. The preparations were allowed to equilibrate for 60 min under continuous superfusion of warm K-B solution and then electrically stimulated at 40 V (0.3 Hz, 3.0 ms). Thereafter, complete noncumulative concentration-response curves were constructed for acetylcholine (ACh), histamine (HIS), potassium chloride (KCl), and barium chloride (BaCl2). Mean Emax (maximal response) values were calculated for each drug. 3. Our study shows that alterations of chemically and electrically evoked contractions are dependent on ischemic periods. It also demonstrates that contractile responses of ischemic tissues to neurogenic stimulation decreases earlier and to a significantly greater extent than the non-nerve mediated responses of the intestinal smooth muscle. Contractile responses to smooth muscle stimulants were all similarly affected by ischemia. Electron microscopy images indicated necrotic neuronal death. The decrease in reactivity of ischemic tissues to electrical stimulation was ameliorated by dexrazoxane, an antioxidant agent. 4. We consider the guinea-pig isolated ileum as a useful model system to study the processes involved in neuronal ischemia, and we propose that the reduction in maximal responses to electrical stimulation is a useful parameter to study neuroprotection.

Pharmacological characterization of urinary bladder smooth muscle contractility following partial bladder outlet obstruction in pigs

Partial bladder outlet obstruction of the pig is considered as a valuable preclinical model for evaluating the profile of compounds for the treatment of bladder overactivity. In this study, we characterized the pharmacological properties of isolated bladder smooth muscle from pigs following partial outlet obstruction and its sensitivity to potassium channel openers. Bladder strips from obstructed animals showed significantly lower maximal efficacy ( E max) and sensitivity to stimulation by ATP and carbachol, but not to those evoked by serotonin, compared to age-matched controls. Tissue strips from obstructed animals also showed a 2.5-fold increase in the potency and significantly reduced maximum response following K + depolarization. With respect to spontaneous activity, bladder strips from control strips demonstrated little spontaneous phasic activity at all preloads examined. In contrast, bladder strips from obstructed animals showed large preload-dependent increases in spontaneous phasic activity at preload values of 16–32 g. The potencies of K ATP channel openers to relax carbachol-evoked contractions showed a good 1 : 1 correlation ( r 2 = 0.90) between obstructed and control bladder strips. These studies demonstrate that obstructed pig bladders show enhanced spontaneous phasic activity especially at elevated preloads, which may underlie unstable myogenic bladder contractions reported in cystometrographic measurements in vivo. The impaired responses to electrical field stimulation could be attributed to reduced efficacies and/or lower sensitivities of muscarinic and purinergic signaling pathways. K ATP channel sensitivities remain essentially unimpaired in the obstructed bladder and could be effectively modulated by openers with potential for the treatment of overactive bladder secondary to outlet obstruction.

The place of partial agonism in psychiatry: recent developments

Drugs used to treat psychiatric disorders, although effective, are often restricted by adverse events. The use of partial agonists for treating hypertension was found to limit some of the side-effects in some patients. This led to the investigation of partial agonists as a treatment modality in psychiatric disorders. Partial agonists have a lower intrinsic efficacy than full agonists leading to reduced maximum response. They can act as antagonists by competing for receptor binding with full agonists. The level of activity depends on the level of endogenous receptor activity. Buprenorphine, a partial agonist at the mu-opioid receptor, is used to treat patients with addiction and decreases the symptoms of withdrawal and risks of overdose and intoxication. The anxiolytic buspirone shows partial agonism at 5-HT(1A) receptors, and this seems to provide anxioselective effects, without inducing extrapyramidal side-effects, convulsions, tolerance or withdrawal reactions. In schizophrenia, partial dopamine agonism results in antagonistic effects at sites activated by high concentrations of dopamine and agonistic effects at sites activated by low concentrations of dopamine. This stabilizes the dopamine system to effect antipsychotic action without inducing adverse motor or hormonal events. Aripiprazole is the first 'dopamine system stabilizer', and the data are promising, with efficacy at least equivalent to that with current atypical antipsychotics but fewer of the troublesome side-effects. Partial agonists seem to provide a way to fine-tune the treatment of psychiatric disorders by maximizing the treatment effect while minimizing undesirable adverse events.