Relevance of seminal plasma nitric oxide levels and the efficacy of SSRI treatment on lifelong premature ejaculation.

The aim of this study was to determine the relevance of seminal plasma nitric oxide (NO) levels and the efficacy of selective serotonin reuptake inhibitor (SSRI) treatment on premature ejaculation. A total of 16 men (aged 32.18 ± 3.32) with lifelong premature ejaculation [intravaginal ejaculation latency time (IELT) <1 min] and 11 healthy men (control group) were included in this study. The healthy men formed Group 1, and the patients were randomly categorised into two groups. Group 2 patients received 20 mg day(-1) of paroxetine, and Group 3 patients received 50 mg day(-1) of sertraline for 4 weeks. Baseline and post-treatment findings were compared among the three groups. Mean baseline seminal NO levels in men with premature ejaculation were significantly higher than in the healthy control group (32.24 ± 5.61 µm l(-1) versus 19.71 ± 3.50 µm l(-1) , respectively) (P < 0.001). There was no significant difference between the sertraline and paroxetine groups in terms of IIEF scores, IELT scores and NO levels. At the end of the first month, the mean IELT scores of the paroxetine and sertraline groups showed a significant improvement compared with the baseline values (P < 0.001). After treatment with paroxetine and sertraline, NO levels dec-reased from baseline. Our study indicates that premature ejaculation is significantly related with a higher level of seminal NO. Baseline seminal plasma NO values obtained in patients with premature ejaculation were significantly higher than in the healthy control group. After treatment with SSRIs, decreased seminal NO may retard ejaculation. Further studies are needed to confirm this suggestion and the role of NO in the pathophysiology and treatment of premature ejaculation.

The effect of long-term resveratrol treatment on relaxation to estrogen in aortae from male and female rats: role of nitric oxide and superoxide.

Resveratrol, which is found in several foods, has vasorelaxing and estrogen-like activities. The aim of the present study was to determine whether the relaxation to estrogen is differently modified between male and female genders after long-term resveratrol treatment. To test this, we compared endothelium-dependent and -independent relaxations to estrogen in the aortae of control and resveratrol-treated male and female rats. Nitric oxide and superoxide levels were also evaluated to explain the mechanism of action of resveratrol. Concentration-response curves to estrogen (10(-10)-10(-4) M) were obtained in aortic rings with and without endothelium from control or long-term resveratrol-treated (50 mg/l in drinking water for 21 days) male and female rats. Estrogen produced mainly endothelium-dependent relaxation in aortic rings of rats, with a higher potency in females than males. Resveratrol treatment increased both endothelium-dependent and -independent relaxations to estrogen especially in aortae from males. The relaxations to estrogen in the aortae of resveratrol-treated rats were inhibited, almost to the same extent as those of control, by pretreatment with ICI 182,780 (10(-6) M), an estrogen receptor antagonist. In both genders, resveratrol treatment increased basal nitric oxide and nitrite/nitrate productions and decreased both basal and NAD(P)H-induced superoxide productions in the aortae. In addition, plasma estrogen levels were found decreased in long-term resveratrol-treated animals of both genders. The improvement in the relaxations to estrogen observed in resveratrol-treated animals could be related to elevated nitric oxide and/or decreased superoxide productions and possibly mediated by classical estrogen receptors. The modulating effect of resveratrol on estrogen responsiveness may differ between male and female.

Ligand efficacy and affinity in an interacting 7TM receptor model.

Quantitative understanding of the activation of G protein-coupled receptors is based mostly on some theoretical models that describe the interaction between ligand and protein partners and the activation process of the receptor. All of these models provide different definitions for observable affinity or efficacy. However, the property common to such parameters defined in the context of these models is that they are always independent of the concentration of the receptor molecule. This is based on the assumption that receptors do not interact with each other appreciably. In this article, experimental evidence for which this assumption does not seem to apply is discussed and an oligomerization model for seven-transmembrane-domain receptors that explains the relationship between receptor concentration, apparent affinity and efficacy is provided.

The effects of agonist stimulation and beta(2)-adrenergic receptor level on cellular distribution of gs(alpha) protein.

This study examines the effects of adrenergic ligands, cholera toxin, forskolin, and varying levels of beta(2) adrenergic receptors (beta(2)AR) on the cellular distribution of Gs(alpha) subunits in CHO cells. Localization of Gs(alpha) was evaluated by confocal microscopy and beta(2)AR-mediated signalling was assessed by adenylyl cyclase (AC) activity. In cells expressing 0.2 pmol/mg protein beta(2)ARs (WT18), the localization of Gs(alpha) subunit was restricted to the plasma membrane region. Isoproterenol (ISO), cholera toxin or forskolin elicited redistribution of cellular Gs(alpha) so that Gs(alpha) appeared as intense spots throughout the plasma membrane as well as the cytoplasm. Exposure to a neutral beta(2)AR antagonist, alprenolol, prevented the ISO-stimulated Gs(alpha) translocation from peripheral to inner cytoplasm. In cells expressing high level of beta(2)ARs (8.2 pmol/mg) (WT4), basal and ISO-stimulated AC activities were significantly elevated when compared to the values detected in WT18 clone, suggesting a positive correlation between receptor expression and receptor-mediated signalling. Basal Gs(alpha) distribution in this group was similar to that observed in ISO-, cholera toxin-, or forskolin-stimulated WT18 clone. ISO, cholera toxin, or forskolin did not change the distribution of Gs(alpha) significantly when tested in WT4 clone. No difference in the cellular level of Gs(alpha) protein between WT18 and WT4 clones was detected. Alprenolol did not affect the distribution of Gs(alpha) in WT4 clone. ICI 118,551, a negative beta(2)AR antagonist, altered Gs(alpha) distribution from a dispersed basal pattern to a membrane-confined pattern. The latter appearance was similar to that observed in unstimulated WT18 clone. Taken together, these data suggest that: (1) enhanced beta(2)AR-Gs(alpha) coupling induced by agonist stimulation or by increased expression of beta(2)ARs remodel the cellular distribution of Gs(alpha); (2) the alteration in Gs(alpha) distribution induced by beta(2)AR overexpression provides evidence for agonist-independent interaction of beta(2)AR and Gs(alpha), that can be inhibited by a negative antagonist but not by a neutral antagonist; and (3) forskolin influences the activity state of Gs(alpha) that displays a Gs(alpha) distribution pattern comparable to that observed when Gs(alpha) is activated via beta(2)AR stimulation or directly by cholera toxin.

Effect of Candida albicans septicemia on the cardiovascular function of rabbits.

Candida albicans is an opportunistic pathogen that causes life-threatening systemic infection in immunocompromised host. However, little is known about the effects of yeast on the cardiovascular functions. This study examined the effects of C. albicans septicemia on the heart and vessel functions and nitric oxide (NO) production in infected rabbits. Anaesthetized animals were challenged with intravenous C. albicans (6 x 10(8)/kg) or saline and the blood pressure of rabbits were measured over 5 h. After that response of the isolated thoracic aorta, right atrium and left papillary muscle were recorded. Blood pressure significantly decreased in the infected rabbits during the septicemia but in the control animals it was stable. The blood nitrite levels and NO-synthases (eNOS, iNOS) expression and tissue nitrite levels in the heart and aorta were similar in the both groups. In the aorta isolated from C. albicans-infected rabbits, acetylcholine-induced endothelium-dependent relaxation was decreased, but contractions induced by phenylephrine were potentiated. The NOS inhibitor, L-N(G)-nitro-arginine methyl ester (L-NAME)-induced contraction increase in the right atrium was depressed by the yeast-infection. In the heart and aorta, microscopic examination revealed no tissue invasion of C. albicans. These results indicate the ability of C. albicans-induced septicemia to destroy NO-related responses of the heart and aorta and may have important implications for functional damage to endothelium and the regulation of cardiovascular functions. In addition, NOS induction and NO over-production are not stimulated by systemic C. albicans infection, which would alter the host immune reaction and homeostasis.

Age-related changes in angiotensin II-stimulated vascular contraction and inositol phosphate accumulation in Fischer 344 rats.

This study examined the influence of age on angiotensin II (AII)-stimulated vascular contractile responses and inositol phosphate (IP) accumulation in Fischer 344 rats. In the aorta, AII-stimulated contraction and IP accumulation were markedly reduced in 6- and 24-month-old rats compared to 1-month-old rats. There was not a significant difference in the contractile response to AII between 6- and 24-month-old rats, although IP hydrolysis showed a further decrease between 6 and 24 months. In tail artery, there were no differences in contraction and phosphoinositol metabolism in response to AII in the different ages. Losartan blocked AII-stimulated vascular contraction and IP hydrolysis in both aorta and tail artery while PD123319 did not inhibit either response. These data indicate that during maturation, there is a decline in AII-stimulated aortic contraction and IP accumulation in aorta but not in tail artery and these changes are due to altered AT1 receptor function.

Effects of dietary restriction on the change in aortic alpha 1-adrenoceptor mediated responses during aging in Fischer 344 rats.

These studies examine changes in alpha 1-adrenoceptor-stimulated contraction, accumulation of inositol phosphates (IPs) and calcium influx during aging, and the effect of dietary restriction. The potency of norepinephrine (NE) at stimulating aortic contraction was highest in aortas from 1-month-old rats compared to 6- or 24-month-old rats, while the potency at stimulating IP accumulation was higher in 6- and 24-month-old rats. The fact that the NE potency for IP accumulation is not decreased with age and is even increased a little, indicates that PI hydrolysis is not limiting for contraction. The data from 24-month-old dietary restricted rats support the same idea. Dietary restriction greatly increased the potency of NE for IP accumulation in the old animals (by 20-fold), but did not restore potency for contraction. Nifedipine (1 microM), a calcium channel blocker, inhibited the NE-stimulated aortic contractile response by 28% in 1-month, 40% in 6-month, and 67% in 24-month-old rats. While nifedipine did not inhibit NE-stimulated IP accumulation in 1-month-old aortas, it inhibited by 30% in 6-month-old aortas and by 27% in 24-month-old aortas. Dietary restriction (DR) did influence the inhibitory effects of nifedipine. Nifedipine inhibition of NE-stimulated contraction in 24-month-old DR rats was comparable to the inhibition in 6-month-old ad libitum (ad lib) controls and was less than in 24-month-old controls. Furthermore, nifedipine was less effective at inhibiting NE-stimulated IP accumulation in aortas from 24-month-old DR rats compared to 24-month-old controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Decrease in apparent alpha1-adrenoceptor-G protein coupling during maturation in rat aorta.

We have previously shown that the adrenoceptor agonist norepinephrine (NE) is more potent in eliciting contraction in aortas from 1-month-old Fischer 344 rats than it is in older animals. In the present study, we examined alpha1-adrenoceptor-guanine nucleotide regulatory binding protein (G protein) coupling in aortic membranes in order to investigate the mechanism for the age-dependent reduced responsiveness of aorta to NE. We used the guanosine 5'(betagamma-imido)triphosphate (Gpp[NH]p)-induced shift in agonist binding affinity as a measure of the efficiency of alpha11-adrenoceptor-G protein coupling. The binding of NE was assessed by measuring the displacement of 2-[beta-(4-hydroxy-3-[125I]iodophenyl)ethylaminomethyl] tetralone ([125]-HEAT) by NE in aortic membranes. In 1-, 6-, and 24-month-old rat aortas, two apparent binding sites were detected in the competition isotherms for NE. This heterogeneous binding pattern was independent of Gpp(NH)p at all ages, and is likely to be due to a heterogeneous receptor population (alpha(1a), alpha(1b), and alpha(1d) subtypes). In 1-month-old rats, the high affinity binding of NE to alpha,-adrenoceptors was sensitive to Gpp(NH)p, indicating a significant interaction between the receptor and G protein. This Gpp(NH)p-sensitive high affinity binding was not observed in aortas from 6- or 24-month-old animals. Despite the lack of Gpp(NH)p-sensitive high affinity binding of agonist in 6- or 24-month-old aortas, NE was still able to induce maximal contraction in these aortas, albeit, with a relatively low potency. A partial reduction in alpha1-adrenoceptor-G protein coupling between 1 and 6 months of age can explain the observed decrease in ago- nist potency and the loss of Gpp(NH)p-sensitive high affinity binding of NE. This phenomenon can be explained as a reduction of allosteric coupling between the bindings of ligand and G protein to the receptor, that has been formulated in the ternary complex model. Computer simulation using the simple ternary complex model shows that manipulating the reciprocal coupling factor alone can lead to a loss of Gpp(NH)p-sensitive high affinity agonist binding, along with a reduction in agonist potency for contraction without altering the maximal response. Thus, a change in the relative expression of different alpha,-adrenoceptor subtypes, which we have previously observed in the aorta, and which possess diverse intrinsic allosteric couplings, may be speculated to be the mechanism for the apparent reduction of alpha,-adrenoceptor-G protein coupling during maturation.

Quasi-irreversible binding of agonist to beta-adrenoceptors and formation of non-dissociating receptor-G(s) complex in the absence of guanine nucleotides.

Here, we tested the hypothesis that receptor-G protein and agonist may form an irreversible complex in the absence of guanine nucleotides. We used the beta-adrenoceptor-G(s) system of guinea pig lung parenchymal membranes as a model. Two groups of membranes were used in the experiments: (1) washed with nucleotide-free buffer in the presence of isoproterenol (isoproterenol-treated), and (2) washed with buffer alone or with agonist+GDP (both were treated as control). Results were as follows: (1) the iodopindolol binding capacity of isoproterenol-treated membranes was reduced by about 30%. (2) No such reduction was observed in control membranes. (3) Addition of GDP to the isoproterenol-treated membranes completely restored the pindolol binding capacity. We interpreted this result as indicating irreversible agonist-receptor complex is formed when the receptor interacts with nucleotide-free G(salpha). (4) We observed a single peak of beta(2)-adrenoceptor activity in the control group by size-exclusion chromatography of the solubilized membranes. Inclusion of isoproterenol in the washing buffer led to an additional (heavier) peak of beta(2)-adrenoceptor activity. This peak disappeared when GDP was added to the detergent extract before high-pressure liquid chromatography (HPLC) analysis. Western blot analysis of these HPLC fractions showed that the agonist-induced heavier peak contained significantly more G(salpha) protein than did the other fractions. We interpreted this result as indicating that a practically irreversible complex of receptor and G protein is formed in the absence of GDP. We suggest that the tightly bound (nucleotide-free) receptor-G protein complex also contains the agonist, and that this complex can be reversed only by the addition of nucleotides. The implications of these results are also discussed.

Alpha 1-adrenoceptor responsiveness in the aging aorta.

Previous studies from this laboratory have shown that aortic alpha 1-adrenoceptor-mediated responsiveness is altered during maturation and aging. This study examines the possibility that there is a change in the alpha 1-adrenoceptor subtypes in the aorta during maturation and aging. The apparent affinity of norepinephrine, as determined by partial receptor inactivation with the alpha 1-adrenoceptor antagonist phenoxybenzamine, was found to be higher in 1-month-old rats compared to 6- and 24-month-old rats. The alpha 1B-adrenoceptor subtype-selective antagonist chlorethylclonidine was used to examine possible heterogeneity in aortic alpha 1-adrenoceptors. The inhibitory effect of chlorethylclonidine on norepinephrine-stimulated contraction was greater in young animals compared to aged animals. Chlorethylclonidine blocked norepinephrine-stimulated inositol phosphate accumulation in 1-month-old aorta but it produced only partial inhibition in the 6- and 24-month-old aortas. The relatively non-selective alpha 1-adrenoceptor antagonists phenoxybenzamine (0.1 microM) and prazosin (0.1 microM) inhibited inositol phosphate accumulation and contractile responses in all ages. The complete block of alpha 1-adrenoceptor-mediated responses by chlorethylclonidine in younger animals shows that alpha 1-adrenoceptor-mediated responses are mediated by the chlorethylclonidine-sensitive alpha 1-adrenoceptor subtypes. The partial inhibition by chlorethylclonidine of alpha 1-adrenoceptor-mediated responses in 6- and 24-month-old animals indicates an increased role of an alpha 1-adrenoceptor subtype that is relatively insensitive to chlorethylclonidine.

Short-term effects of three continuous hormone replacement therapy regimens on platelet tritiated imipramine binding and mood scores: a prospective randomized trial.

OBJECTIVE: To evaluate the effects of continuous hormone replacement therapy (HRT) regimens on platelet-tritiated ((3)H-) imipramine binding (Bmax) and mood. DESIGN: Prospective randomized study. SETTING: University hospital. PATIENT(S): Sixty postmenopausal patients. INTERVENTION(S): Randomization to 3 months of daily treatment with tibolone and conjugated equine estrogen (CEE).625 mg combined either with 2.5 or 5 mg of medroxyprogesterone acetate (MPA). The inclusion criteria-matched patients declined for HRT were prescribed daily alendronate. Pre- and posttreatment blood sampling for Bmax and mood evaluation with the Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory (STAI) were done. MAIN OUTCOME MEASURE(S): Pre- and posttreatment Bmax and mood scores. RESULT(S): As compared with baseline, both CEE+MPA regimens and tibolone significantly increased Bmax. The comparisons of percent change from baseline Bmax for the CEE+MPA and tibolone groups were similar. All three HRT regimens improved the BDI significantly, while there were no significant changes in the STAI. In the alendronate group, there were no significant changes in both pre- and posttreatment Bmax and mood scores. CONCLUSION(S): Continuous treatment with CEE+MPA and tibolone increases platelet (3)H-imipramine binding and improves mood. Mood-enhancing effects of tibolone may occur through the serotonergic system, as is the case with estrogen.

Prenatal cocaine exposure alters norepinephrine release from cardiac adrenergic nerve terminals.

The effect of prenatal cocaine exposure on the development of the cardiac adrenergic nervous system was assessed in neonatal rabbits. Pregnant does received cocaine (4 mg/kg, i.v., bid) or saline during gestational days 8 to 29. Hearts were obtained on postnatal days 10, 20, 30, and 50. Adrenergic nerve function was assessed by measuring 3H-norepinephrine (NE) uptake and 3H-NE release from cardiac synaptosomes. NE uptake increased with postnatal age and was not affected by cocaine exposure. K(+)-induced NE release increased with age, was significantly less in cocaine exposed rabbits compared to saline exposed rabbits at days 10, and 20, but was similar at days 30 and 50. NE release induced by ionomycin, a Ca2+ ionophore, did not change with age, was significantly greater in cocaine exposed rabbits compared to saline exposed rabbits at days 10, 20, and 30, but was similar at day 50. Wet heart weight, heart weight per body weight, and NE content of the hearts were not affected by cocaine exposure. These results suggest that prenatal cocaine exposure delays the development of the mechanisms responsible for Ca2+ influx during K(+)-induced depolarization and increases the neurosecretory response to intracellular Ca2+.

Cardiovascular hypertrophy and increased vascular contractile responsiveness following repeated cocaine administration in rabbits.

The effects of repeated cocaine administration on contractile responses were studied in adult rabbits. Repeated cocaine exposure caused a significant increase in the maximal response of the aorta to the agonists norepinephrine and serotonin as well as the receptor- independent stimulus KCl when compared to the saline controls. Cocaine exposure caused a significant increase in the wet weights of both heart and aorta. When the contraction was normalized to the wet weight of the aorta there was no difference between rabbits administered cocaine and saline. Acute cocaine administration caused a time-dependent increase in immunoreactivity of the proto-oncogene c-Fos in the aorta. These results show that repeated cocaine administration leads to the development of cardiovascular hypertrophy.

Prenatal cocaine exposure affects the development of aortic adrenergic innervation and contractile responses.

This study examines the effects of prenatal cocaine administration on the development of vascular sympathetic innervation and contractile responsiveness. Rabbits received cocaine (4 mg/kg, iv, bid) or saline during gestational days 8 to 29. Aortas were obtained on postnatal days 10, 20, 30 and 50. Vascular smooth muscle responsiveness was assessed by measuring aortic contractile responses to norepinephrine (NE) and to other vasoconstrictors. Vascular adrenergic innervation was evaluated by measuring desipramine sensitive [3H]-NE uptake into aortic ring segments and aortic NE content. [3H]-NE uptake and NE content were reduced at postnatal days 10 and 20 in the rabbits exposed prenatally to cocaine. Differences were not observed at postnatal days 30 or 50. The contractile response to NE was reduced in rabbits exposed to cocaine prenatally. Maximal response and potency were decreased at postnatal day 10 and potency was still decreased at day 20, but not at the older ages. Contractile responses to serotonin (5-HT) and angiotensin II (AII) were not affected by prenatal cocaine exposure. These results suggest that prenatal cocaine exposure delays the development of aortic adrenergic innervation and alpha adrenoceptor responsiveness.

Spleen damage in endotoxaemic mice: the involvement of nitric oxide.

The association between Escherichia coli endotoxin-induced organ damage and nitric oxide-related mechanisms was investigated in the spleen of male Swiss albino mice (20-40 g) by using (1) Pt/Ir electrochemical sensor connected to an amperometric detection system (NO-501, InterMedical Co., Japan), (2) nitrotyrosine immunohistochemistry, (3) conventional light microscopy and (4) immunoblotting techniques in parallel. 1 h before endotoxin injection, animals were pretreated with either nitric oxide synthase inhibitor, L-N(G)-nitroarginine methyl ester (L-NAME, 20 mg kg(-1), i.p.) or inducible nitric oxide synthase expression inhibitor, dexamethasone (5 mg kg(-1), i.p.) or the inhibitor of murine inducible nitric oxide synthase in vivo, 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT, 1 mg kg(-1), i.p.). 5 h after endotoxin treatment, electrochemically detected concentration of nitric oxide was significantly elevated (nM, endotoxin: 716.6 +/- 178.2, n = 10 vs saline: 209.4 +/- 127.8, n = 9, P = 0.0312, unpaired Student's t-test) and remained so throughout the 30 min monitorization period. Neither dexamethasone nor AMT blocked the endotoxin-induced overproduction of nitric oxide indicating that the enhanced inducible nitric oxide synthase activity cannot be the only explanation. When dexamethasone and L-NAME combination was used to block both the constitutive and the inducible isoforms, nitric oxide production was virtually abolished, indicating a significant contribution from the constitutive isoform of nitric oxide synthase. The results of nitrotyrosine immunohistochemistry and the conventional light microscopy were also in agreement with the amperometric method while immunoblotting revealed the expression of both the endothelial and the inducible isoforms of nitric oxide synthase were induced endotoxaemic animals. Thus, conclude that endotoxin-induced splenic damage in endotoxaemia can be explained by enhanced production of nitric oxide due to the induction of both endothelial and inducible nitric oxide synthases while causal relationship and the roles of other deleterious mediators such as oxygen-derived free radicals are yet to be established.

α1-Adrenoceptor-mediated contraction of rat aorta is partly mediated via transactivation of the epidermal growth factor receptor.

BACKGROUND AND PURPOSE: High level of plasma catecholamines is a risk factor for vascular diseases such as hypertension and atherosclerosis. Catecholamines induce hypertrophy of vascular smooth muscle through α(1) -adrenoceptors, which in cell culture involves the transactivation of epidermal growth factor receptor (EGFR). We hypothesized that EGFR transactivation was also involved in contractions of rat aorta mediated by α(1) -adrenoceptors. EXPERIMENTAL APPROACH: Thoracic aorta was isolated from 12-14 week old male Wistar rats. In vitro aortic contractile responses to cumulative doses of phenylephrine were characterized in the absence and presence of the EGFR kinase inhibitors, AG1478 and DAPH, in intact and endothelium-denuded rings. Involvement of signal transduction pathways was investigated by using heparin and inhibitors of Src, matrix metalloproteinase (MMP), extracellular signal-regulated kinase (ERK)1/2 and phosphatidyl inositol 3-kinase (PI3K). Phosphorylation of EGFR and ERK1/2 was measured after short-term phenylephrine or EGF stimulation in aorta segments in the presence of AG1478 and the PI3K inhibitor, wortmannin. KEY RESULTS: AG1478 and DAPH concentration dependently attenuated phenylephrine-induced contractile responses in intact or endothelium-denuded aortic rings. Inhibition of PI3K (wortmannin and LY294002) but not heparin or inhibitors of Src or MMP, prevented the effect of AG1478 on the responses to phenylephrine. Phenylephrine induced phosphorylation of EGFR, which was partially blocked by AG1478. Phenylephrine also increased phosphorylation of ERK1/2, time-dependently and was blocked by AG1478 and wortmannin. CONCLUSIONS AND IMPLICATIONS: Contractions of rat thoracic aorta mediated by α(1) -adrenoceptors involved transactivation of EGFR, mediated via a PI3K and ERK1/2 dependent pathway.

Heterogeneous inhibitory effect of nitrendipine on 5-HT-responses in rabbit vascular tissues.

1. Sensitivity of 5-HT2 receptor mediated vascular responses to calcium channel antagonism was investigated in the rabbit thoracic aorta, common carotid artery and main pulmonary artery considering tissue-state of receptor reserve and agonist efficacy. 2. Although 5-HT2 receptor reserve seems to be similar in these preparations, nitrendipine had a heterogeneous inhibitory effect on the contractile response to 5-HT. 3. Reducing 5-HT2 receptor reserve by phenoxybenzamine caused an increase in the inhibitory effect of nitrendipine in these vascular tissues. 4. The vasoconstrictor response induced by 5-carboxyamidotryptamine (5-CT), which is a less potent agonist, showed greater sensitivity to nitrendipine antagonism than the response to 5-HT. 5. The results suggest that efficacy of agonists and tissue-state of receptor reserve seem to be important factors which are partially responsible for the inhibitory effect of nitrendipine on the contractile responses mediated by 5-HT2 receptors.

Effects of calcium channel blockers on formalin-induced nociception and inflammation in rats.

The possible anti-inflammatory and antinociceptive effects of nitrendipine, nicardipine, diltiazem and verapamil were examined with formalin test in the rat paw. Pretreatment with these calcium channel blockers 1 h before formalin injection diminished formalin-induced inflammatory changes and nociceptive responses. Formalin-induced nociceptive responses were inhibited 20-90% by the calcium channel blockers. Nitrendipine and nicardipine were found to be highly effective in inhibiting the inflammatory changes, whereas the effects of verapamil and diltiazem were partial. Administration of naloxone affected neither the inflammatory changes and nociceptive responses induced by formalin nor the antiinflammatory and antinociceptive effects of the calcium channel blockers. The results suggest the possible anti-inflammatory and naloxone-insensitive antinociceptive properties of calcium channel blockers.

The effects of ions on antibacterial activity of ofloxacin and ceftriaxone.

MIC and MBC values of ofloxacin and ceftriaxone were investigated against Staphylococcus aureus in MHB and MHB containing additional Mg2+, Al3+, Fe3+, Ca2+, Zn2+, Cu2+. The addition of Mg2+, Al3+, Fe3+ increased the MIC and MBC of ofloxacin and the MBC of ceftriaxone. However, the addition of these cations did not change the MIC of ceftriaxone. Our findings suggest that these interactions might be due to the formation of chelates between metal ions and antibiotics. These results also indicate that some cations may have an important role in the antibacterial activity of antibiotics.

Beta-adrenoceptor-G alpha S coupling decreases with age in rat aorta.

beta-Adrenoceptor (beta AR) responsiveness, receptor density, receptor-G protein coupling, and the possible role of membrane fluidity in receptor-G protein coupling were investigated in the rat aorta with age. The beta AR agonist isoproterenol (ISO) produced relaxation of KCl-induced aortic contractions by 97%, 21%, and 0% in aortae from 1- 6-, and 24-month-old Fischer 344 rats, respectively. Forskolin completely relaxed the contractions at all ages. beta AR density was determined in aortic membranes by saturation binding of 125I-cyanopindolol (125I-CYP). beta AR density was 76, 52, and 47 fmol/mg of protein in 1-, 6-, and 24-month-old rats, respectively. To investigate beta AR coupling to G proteins, displacement by ISO of 125I-CYP binding was determined in aortic membranes in the presence and absence of the GTP analog guanosine-5'-(beta gamma-imido)triphosphate [Gpp(NH)p] (0.1 mM). The effect of Gpp(NH)p on the ISO displacement curve for 125I-CYP binding was greatest in 1-month-old rats and decreased markedly with age. In 1-month-old aorta, in the absence of Gpp(NH)p the ISO displacement curve was biphasic and two affinity constants were determined (KH - 0.061 microM and KL = 2.4 microM). In the presence of Gpp(NH)p the ISO displacement curve was monophasic (Kd - 0.72 microM). In 6-month-old aorta, whereas an effect of Gpp(NH)p on the ISO displacement curve could still be observed [in the absence of Gpp(NH)p, KH = 0.2 microM and KL = 3.5 microM; in the presence of Gpp(NH)p, Kd - 0.83 microM], the affinity constant for high affinity agonist binding and the percentage of receptors with high affinity for agonist were decreased significantly. In 24-month-old aorta there was no effect of Gpp(NH)p on the ISO displacement curve and a single affinity constant was detected [0.7 microM and 0.8 microM in the presence and absence of Gpp(NH)p, respectively]. The presence of two affinity constants for ISO in 1- and 6-month-old aorta in the absence of Gpp(NH)p and single affinity constants in the presence of Gpp(NH)p presumably represent the G protein-coupled and uncoupled states of the beta ARs, which are not observed in 24-month-old aorta. The ability of the beta AR to form the high affinity nucleotide-sensitive complex with the agonist was restored by treatment of the membranes with cis-vaccenic acid, which increases the fluidity of the membrane.(ABSTRACT TRUNCATED AT 400 WORDS)