Multidisciplinary management of acute cholecystitis during the COVID-19 pandemic.

The coronavirus disease 2019 pandemic had a major impact on most medical services. Our aim was to assess the outcome of acute cholecystitis during the nationwide lockdown period. All patients admitted to our emergency department for AC were analysed. Patient characteristics, performance status, AC severity, treatment modality and outcome of AC were assessed during the lockdown period (Period II: 1 April 2020-30 November 2021) and compared to a historical control period (Period I: 1 May 2017-31 December 2018). AC admissions increased by 72.8% in Period II. Patients were younger (70 vs. 74 years, p = 0.017) and greater in number in the CCI 1 group (20.4% vs. 11.2%, p = 0.043) in Period II. The unplanned readmission rate (6.3 vs. 0%, p = 0.004) and the gallbladder perforation (GP) rate was higher (18.0 vs. 7.3%, p = 0.006) in Period II. Percutaneous transhepatic gallbladder drainage (PTGBD) was more frequent (24.1 vs. 12.8%, p = 0.012) in Period II. In addition to a drop in patient age and CCI, a significant rise in the prevalence of acute cholecystitis, GP and unplanned readmissions was observed during the nationwide lockdown due to the COVID-19 pandemic. PTGBD was more frequent during this period, whereas successful conservative treatment was less frequent.

Effect of Vitamin D Status on Vascular Function of the Aorta in a Rat Model of PCOS.

Polycystic ovary syndrome (PCOS) is associated with elevated cardiovascular risk. Early vascular dysfunction may lead to the development of cardiovascular disease in PCOS. Vitamin D deficiency (VDD) is a common comorbidity of PCOS that contributes to the pathogenesis of the disease and its complications. Both PCOS and VDD are accompanied by increased oxidative stress that may be involved in the arising vascular dysfunction. We aimed to investigate the role of vitamin D status on aortic function. PCOS was induced by an 8-week-long transdermal testosterone treatment of female rats, and low and adequate vitamin D status was achieved by dietary means. Contraction and relaxation abilities of isolated aortic segments were measured by myograph. Resorcin-fuchsin staining and immunohistochemical labeling of 3-nitrotyrosine were performed. No difference was shown in the norepinephrine-induced contraction of the aortas of different groups, whereas we detected reduced acetylcholine- and insulin-evoked relaxation in VDD groups. A lower level of resorcin-fuchsin staining and elevated 3-nitrotyrosine immunostaining was observed in VDD. In our study, we demonstrated early endothelial dysfunction in VDD PCOS rat model. Vitamin D supplementation could prevent vascular disturbances, while VDD itself damaged endothelium-dependent vasorelaxation and induced nitrative stress.

Evaluation of oxidative/nitrative stress and uterine artery pulsatility index in early pregnancy.

INTRODUCTION: Increased oxidative/nitrative stress is characteristic not only in pathologic, but also in healthy pregnancy. High uterine artery pulsatility index (UtAPI) at the end of the first trimester is associated with altered placentation and elevated risk for adverse pregnancy outcomes. We aimed to examine the relationship of systemic oxidative/nitrative stress and uterine artery pulsatility index in the first trimester and their correlation to pregnancy outcomes. MATERIAL AND METHODS: Healthy pregnant women were recruited at 12-13th gestational week ultrasound examination; UtAPI was determined by color Doppler ultrasound. Patients were divided into high (UtAPI ≥ 2.3) (n = 30) and low (n = 31) resistance groups, and pregnancies were followed until labor. Systemic oxidative/nitrative stress was estimated by measuring total peroxide level, total antioxidant capacity and nitrotyrosine level. RESULTS: Plasma total peroxide level was significantly lower (2,510 ± 39 µM vs. 2,285 ± 59 µM), total antioxidant capacity was higher (781 ± 16 mM CRE vs. 822 ± 13 mM CRE) in the high UtAPI group, which were accompanied by lower birth weight (3,317 ± 64 vs. 3,517 ± 77 g, P < 0.05). Plasma total peroxide level showed a negative correlation (by Pearson) to UtAPI (P < 0.01) and positive correlation to birth weight (P < 0.05). CONCLUSIONS: According to our results, lower systemic oxidative stress showed correlation with high UtAPI measured between the 12-13th weeks of gestation. We also found significant differences in the birth weight of healthy newborns; therefore it is worth examining this relationship in pathological pregnancies.

Use of glucose-lowering drugs in Hungary between 2008 and 2017: the increasing use of novel glucose-lowering drug groups.

AIMS: To analyse glucose-lowering drug utilization, focusing on the novel glucose-lowering drug groups dipeptidyl peptidase-4 inhibitors, glucagon-like peptide-1 receptor agonists and sodium-glucose co-transporter-2 inhibitors, and the financial burden they entail. METHODS: Crude reimbursed national drug utilization and expenditure data for the entire population of Hungary were obtained from the National Health Insurance Fund for the study period: 2008 to 2017. Data were analysed using the WHO's Anatomical Therapeutic Chemical Classification/defined daily dose system and were expressed in defined daily dose per 1000 inhabitants per day. RESULTS: Total glucose-lowering drug consumption in Hungary showed an 18% increase over the study period, reaching 74.7 defined daily doses per 1000 inhabitants per day, while novel glucose-lowering drug use increased to 11.7 defined daily doses per 1000 inhabitants per day (16% of total glucose-lowering drug use) by 2017. Dipeptidyl-peptidase 4 inhibitor consumption grew to 7.4 defined daily doses per 1000 inhabitants per day by 2017. The most widely used dipeptidyl-peptidase 4 inhibitor was sitagliptin. Glucagon-like peptide-1 receptor agonists were used the least, but by 2017 rose to 1.5 defined daily doses per 1000 inhabitants per day, led by liraglutide. Sodium-glucose co-transporter-2 inhibitors appeared in the utilization data in 2014 and their consumption, mainly empagliflozin, reached 2.8 defined daily doses per 1000 inhabitants per day by 2017. The total expenditure on glucose-lowering drugs increased 94% between 2008 and 2017, and the total cost of novel glucose-lowering drug utilization comprised 44% of the total glucose-lowering drug expenditure in 2017. CONCLUSIONS: Both the use of and the financial burden posed by novel glucose-lowering drugs in Hungary increased steadily between 2008 and 2017. This increase is expected to continue.

New formulation of in situ gelling Metolose-based liquid suppository.

CONTEXT: An in situ gelling liquid suppository is liquid at room temperature but forms a gel at body temperature. In our work, Metolose® SM-4000 (methylcellulose) is studied that basically shows thermal gelation at 68°C (2%, w/w). OBJECTIVE: The objective was to study the potency of different factors (concentration, pH, additives) to change the value of thermal gelation temperature (T (t)) for Metolose® to form an in situ gelling liquid suppository. MATERIALS AND METHODS: We studied the effect of Metolose® concentration, pH, and salts (sodium chloride, potassium chloride, sodium hydrogen carbonate, and sodium monohydrogen phosphate) on T (t) by viscosimetry. To choose the appropriate compound, in vitro drug release was examined. Rectal safety test was performed on rats in vivo after 12-hour application. RESULTS: Increasing the Metolose® concentrations (0.5-4%, w/w), T (t) can be decreased, but it also altered the consistency of gel. pH does not affect the T (t). The water-soluble salts allowed reducing the gelation temperature to 37°C. Sodium monohydrogen phosphate in 4.5% concentration was found to be the most appropriate. The impact of examined factors on in vitro drug release of piroxicam from the in situ-formed gel was characterized according to Fickian diffusion. Metolose® and the chosen salt did not cause any morphological damage on the rectal tissues. DISCUSSION: According to our study, Metolose® has the physical and chemical potential to be used as base for liquid suppositories.

In vitro pharmacology of inosine, with special reference to possible interactions with capsaicin-sensitive mechanisms and inflammatory mediators.

The in vitro pharmacology of inosine (Ino), a putative anti-inflammatory compound, has been investigated in smooth muscle preparations, with emphasis on its possible interaction with known inflammatory mediators, as well as capsaicin, an inducer of "neurogenic inflammation". The highest concentration of Ino routinely studied was 1 mM, since 10 mM nonspecifically inhibited many types of smooth muscle motor responses. In the guinea pig isolated ileum or trachea, Ino (1 mM) failed to influence the excitatory effect of capsaicin. The nitric oxide (NO)-mediated relaxant effect of capsaicin in the human colonic circular muscle was not influenced by Ino. Ino only weakly reduced the contractile effect of histamine on the guinea pig ileum. Substance P-mediated nonadrenergic, noncholinergic (NANC) contractions evoked by electrical stimulation in the guinea pig ileum were inhibited by half by Ino (1 mM). Ino showed no or only a weak inhibitory effect on NANC relaxation of the rat ileum. Arachidonic acid- or leukotriene D(4)-induced contractions of the guinea pig ileum were only moderately inhibited by Ino. Collectively, these results indicate that Ino (up to 1 mM) shows no major antagonist activity at histamine H(1) receptors, leukotriene CysLT(1) receptors, the transient receptor potential channel TRPV1 or tachykinin NK(1) or NK(2) receptors, or cyclooxygenase-inhibitory activity. Therefore, its anti-inflammatory activity is probably not associated with these mechanisms. The in vitro methods used in this study are capable of detecting a wide range of biological effects and hence may be recommended as a screening procedure for potential drugs or natural products.

Rapid 'glycaemic swings' induce nitrosative stress, activate poly(ADP-ribose) polymerase and impair endothelial function in a rat model of diabetes mellitus.

AIM/HYPOTHESIS: Postpandrial hyperglycaemia is a significant risk factor for the development of macrovascular diseases. There is no clear agreement in the field whether these alterations result from hyperglycaemic episodes or from exaggerated alterations ('glycaemic swings') in blood glucose. We compared the effect of stable high glucose with a model of poorly maintained insulin-controlled diabetes (on average lower glucose, but with large glycaemic swings) on the development of endothelial dysfunction in rats. METHODS: Intermediate- or long-acting insulin was used to reduce mean blood glucose levels. One group of animals had stable low glucose levels, while animals in the other group exhibited rapid changes ('swings') in their blood glucose concentration. Acetylcholine-induced endothelium-dependent vascular relaxation of the thoracic aorta was measured. Immunohistochemistry, western blot analysis and flow cytometry were used to determine nitrotyrosine formation and poly(ADP-ribose) accumulation in the aorta, in circulating leucocytes and in bone marrow cells. RESULTS: Steady normalisation of blood glucose levels (a model of well-controlled diabetes) protected against the development of endothelial dysfunction, poly(ADP-ribose) polymerase (PARP) activation and nitrotyrosine production. However, impairment of endothelium-dependent relaxation was found in the animals undergoing glycaemic swings, even though the fructosamine levels in these animals were lower than in the untreated diabetic rats. This was associated with elevated PARP activation in the aorta and in bone marrow cells that was similar to or even more pronounced than that seen in the untreated diabetic animals. CONCLUSIONS/INTERPRETATION: Large glycaemic swings exert deleterious cardiovascular effects in diabetes mellitus, in part via enhanced activation of the PARP pathway.

Hungarian hospital antibiotic consumption at the regional level, 1996-2005.

BACKGROUND: Regional variations in antibiotic consumption in outpatients have been reported previously, but nothing is as yet known about the regional distribution of antibiotic consumption in the hospital sector in Hungary. This study was designed to explore regional variations and investigate determinants of antibiotic consumption in hospital care in Hungary. MATERIALS AND METHODS: Regional distribution-based antibiotic sales data were obtained for a 10-year period (1996-2005) for the 20 Hungarian counties. Systemic antibacterial use (Anatomical Therapeutic Chemical code: J01) was expressed as the number of defined daily doses (DDD) per 100 patient-days. The multiple linear regression model was applied to investigate the determinants of regional differences in hospital antibiotic consumption. Independent variables related to health care access, utilization of hospital resources, doctors' workload, type of hospital care provided, and patient's characteristics and infections were considered as possible determinants, and data on these variables were obtained for 2 years (2004, 2005). We also tested the association between hospital and ambulatory care antibiotic consumption in Hungarian regions using the Pearson correlation test. RESULTS: For each year during the 1996-2005 study period, there were large and stable variations in total hospital antibiotic consumption (e.g., min-max(1996): 16.0-28.2; min-max(2005): 15.2-32.2 DDD per 100 patient-days) depending on the region. In the two developed models (Model 1 and Model 2), the number of reported infections accounted for 53% of the observed regional variations in hospital antibiotic consumption (Model 1), and the number of reported infections together with the case-mix index were responsible for 61% (Model 2) . Total antibiotic consumption in hospitals showed a positive correlation (R = 0.71, p = 0.002) with total antibiotic consumption in ambulatory care. CONCLUSION: The case-mix index and the number of reported infections explained some of the observed regional variations. However, the moderate value of the models in explaining these regional variations suggest that determinants which could not be explored in this preliminary study may also contribute to regional differences. Future studies should aim at collecting data for each individual hospital as well as data on possible determinants for hospital antibiotic consumption.

Results of a local antibiotic management program on antibiotic use in a tertiary intensive care unit in Hungary.

BACKGROUND: Massive antibiotic use in intensive care units (ICU) is associated with increased microbial resistance. Therefore avoiding unneccesary antibiotic usage is essential. To achieve a more considered antibiotic prescribing practice, a new antibiotic policy was implemented at our ICU. In this paper, we evaluated the impact of this intervention, and described the aetiology and incidence of blood stream infections and selected antibiotic-resistant pathogens. MATERIALS AND METHODS: In November 2002, a local antibiotic management program (LAMP) was implemented. This included a new infectious diseases specialist consultation service and restricted authorisation to prescribe antibiotics. The effect on ward-level antibiotic use was examined by segmented regression analysis. Patient, ICU and microbiology data were also recorded and compared before and after policy implementation. RESULTS: The patient populations and the subsequent mortality rate were comparable before and after the implementation of the policy. Total antibiotic consumption was markedly reduced from 162.9 to 101.3 defined daily dose (DDD) per 100 patients, and per day (DDD per 100 patient-days). This was mainly accounted for a reduction in the use of quinolones, aminoglycosides, glycopeptides, metronidazol, carbepenems and third generation cephalosporins. CONCLUSION: This study has confirmed that establishing a targeted LAMP, based on close co-operation between intensive care physicians and infectious disease specialists together with a restricted prescribing authority, can reduce the use of antibiotics.

Role of extrinsic afferent neurons in gastrointestinal motility.

Capsaicin-sensitive extrinsic afferent nerves have been demonstrated to release biologically active substances in the gastrointestinal (GI) tract. This fact may be useful for identifying sensory transmitter substances in isolated organ experiments. In the GI tract of animals neuropeptides like tachykinins and calcitonin gene-related peptide (CGRP) mediate specific excitatory and inhibitory effects of capsaicin; some evidence indicates a participation of purinergic mechanisms as well. The human gut (especially the circular musculature) is powerfully relaxed by capsaicin, and this effect seems to have a completely different transmitter background (nitric oxide (NO) and maybe VIP, neither of them of intrinsic neuronal origin). We propose that NO may be a sensory neurotransmitter. The "local efferent" (mediator-releasing) effect of extrinsic afferent neurons can also be demonstrated in vivo, both in animals and man. Yet, nearly normal motility of the small and large intestines (i.e., the most "autonomous" part of the GI tract) is maintained in animals with functionally inhibited capsaicin-sensitive nerves. The importance of this system in regulating GI movements may be exaggerated under pathopysiological conditions, first of all inflammation. The afferent function of capsaicin-sensitive nerves plays a role in sympathetic reflexes, such as the inhibition of GI motility after laparotomy or by peritoneal irritation.

An 8-year evaluation of antibiotic consumption and antibiotic resistance among Streptococcus pneumoniae from in- and out-patients in Szeged, Hungary.

At the beginning of the 1990s, the prevalence of penicillin resistance of Streptococcus pneumoniae strains in Hungary was found to be extremely high (up to 58% non-susceptible) in some studies, while in other publications the percentage of penicillin highly resistant strains was 0-2%. To see whether this was due to differences in methodology or the composition of the patient population studied, a retrospective evaluation was carried out of the penicillin, amoxicillin, ceftriaxone and macrolide resistance of all S. pneumoniae strains isolated from in- and outpatients in our laboratory between 1998 and 2005. Of the 2670 S. pneumoniae isolates only 5.58% was found to exhibit high-level resistance to penicillin, while resistance to amoxicillin, ceftriaxone and erythromycin was 2.62%, 1.12% and 42.06%, respectively. During this period 6 (3.8%) of 155 S. pneumoniae strains isolated from invasive samples displayed high-level resistance to penicillin. Earlier surveillance data on penicillin resistance of S. pneumoniae may have been biased by the age groups affected by the infection, by whether the strain was isolated from an out-patient or an in-patient, and by whether the isolates were obtained from invasive samples. Our 8-year study using the NCCLS/CLSI methodology consequently revealed a low prevalence of high-level resistance to penicillin in S. pneumoniae strains obtained both from adults and children.

P2 purinoceptor antagonists inhibit the non-adrenergic, non-cholinergic relaxation of the human colon in vitro.

Neurotransmitters released by myenteric neurons regulate movements of intestinal smooth muscles. There has been little pharmacological evidence for a role of purinergic mechanisms in the non-adrenergic, non-cholinergic (NANC) relaxation of the human large intestine. We used P(2) purinoceptor antagonists to assess whether such receptors are involved in the NANC relaxation of the circular muscle of the human sigmoid colon. It was also investigated whether the guanylate cyclase enzyme mediates the NANC response. Human colonic circular strips were tested in organ bath experiments with isotonic recording. NANC, non-nitrergic relaxations induced by electrical field stimulation (1 and 10 Hz, in the presence of atropine, guanethidine, and 100 microM N(G)-nitro-L-arginine [L-NOARG]) were strongly inhibited by a combination of the P(2) purinoceptor antagonists pyridoxal-phosphate-6-azophenyl-2',4'-sulfonic acid (PPADS) (50 microM) and suramin (100 microM). PPADS plus suramin was ineffective in the absence of L-NOARG. L-NOARG alone significantly reduced the NANC relaxation to electrical stimulation. PPADS plus suramin strongly inhibited the relaxation in response to exogenous alpha,beta-methylene ATP. The guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (3 microM) inhibited the NANC relaxation, but did not add to its reduction by L-NOARG. L-NOARG was still slightly effective in the presence of ODQ. Vasoactive intestinal polypeptide tachyphylaxis failed to influence the non-nitrergic NANC relaxation. It is concluded that nitric oxide (NO) and ATP co-mediate, in a non-additive manner, the NANC relaxation. NO probably acts through the guanylate cyclase, though a small fraction of its effect might be mediated by other mechanisms. Activators of the guanylate cyclase other than NO do not seem to participate in the NANC relaxation.

Actions of endothelin and corticotropin releasing factor in the guinea-pig ileum: no evidence for an interaction with capsaicin-sensitive neurons.

Both endothelins and corticotropin releasing factor (CRF) appear in capsaicin-sensitive neurons. We have investigated the effects of human endothelin-1 (ET-1) and CRF in the guinea-pig ileum longitudinal and circular preparations and sought for ways of specific antagonism. With the aid of tachyphylaxis to capsaicin (i.e., rendering capsaicin-sensitive neurons functionally impaired) it was tested if these neurons played a mediating role in the effects of ET-1 or CRF. We also tried to find out whether endogenous endothelin or CRF plays a role in the excitatory and inhibitory effects of capsaicin in the ileum. In preparations at basal tone, both exogenous ET-1 (1-100 nM) and CRF (3-100 nM) caused contraction. These responses were not influenced by capsaicin tachyphylaxis. The contractile effect of ET-1 was not affected by tetrodotoxin (1 microM), atropine (1 microM), methysergide (100 nM), chloropyramine (100 nM) or SR140333 (100 nM) but was significantly inhibited or even abolished by the receptor antagonist BQ123 (3 microM) or BQ788 (3 microM). CRF caused contraction that was fully sensitive to tetrodotoxin (1 microM), tachyphylaxis to CRF or to atropine (1 microM) plus the tachykinin NK1 receptor antagonist SR140333 (200 nM). Atropine alone had a weak inhibitory effect on the contractile action of CRF. Neither the antagonist BQ123 (3 microM) nor CRF tachyphylaxis inhibited the contractile action of capsaicin (2 microM), even in the presence of a mixture of GR82334 (3 microM) and SR142801 (100 nM), for blocking tachykinin NK1 and NK3 receptors, respectively--a treatment that by itself significantly reduced the effect of capsaicin. Exogenous ET-1 (0.3-5 nM), but not CRF (30-100 nM), caused relaxation of the atropine-treated, histamine-precontracted ileum. This effect of ET-1 was significantly inhibited or abolished by BQ123 (10 microM), or BQ788 (3 microM), but was not influenced by capsaicin tachyphylaxis. Likewise, relaxation of the atropine-treated, histamine-precontracted ileum in response to capsaicin was not influenced by the endothelin receptor antagonist BQ788 (3 microM) or BQ788 (3 microM) plus BQ123 (3 microM). Apamin (300 nM) was also without effect on the capsaicin-induced relaxation. In circular muscle strips ET-1 inhibited the indomethacin-induced spontaneous activity. This effect was abolished by BQ123 (3 microM) or BQ788 (3 microM). CRF caused a stimulation of the circular muscle. This stimulatory effect was not influenced by atropine (1 microM) alone, but was inhibited by atropine plus tachykinin NK1 and NK2 receptor antagonists (SR140333 (200 nM) and SR48968 (200 nM)) and also by tetrodotoxin (1 microM). It is concluded that capsaicin-sensitive neurons do not play a role in the effects of exogenous ET-1 or CRF in the guinea-pig ileum. ET-1 can both contract and relax the ileal longitudinal smooth muscle directly, probably via both ETA and ETB receptors. CRF acts by specifically stimulating excitatory (but not inhibitory) neurons of the myenteric plexus. Neither endogenous ET-1 nor CRF seems to play a role in the excitatory or inhibitory effects of capsaicin.

Nitric oxide is involved in the relaxant effect of capsaicin in the human sigmoid colon circular muscle.

The relaxant effect of capsaicin (300 nM) has been studied on mucosa-free circular strips of the human sigmoid colon in vitro. The response of precontracted preparations to capsaicin (sub-maximal relaxation) was reduced by over 50% by the nitric oxide synthase inhibitor N(G)-nitro- L-arginine (L-NOARG; 20 microM or 100 microM) or by the guanylate cyclase inhibitor 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 1 microM), but not by tetrodotoxin (1 microM) or the P(2) purinoceptor antagonist pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid (PPADS; 50 microM). L-NOARG or ODQ caused moderate contraction of the circular muscle, indicating a tonic "nitrergic" control. Anandamide (1-100 microM), an endogenous cannabinoid and capsaicin VR(1) receptor stimulant, failed to either mimic or modify the response to capsaicin (300 nM). It is proposed that capsaicin causes the release of smooth muscle relaxant substance(s) from afferent nerve endings in the gut wall, in a tetrodotoxin-resistant manner. Nitric oxide (possibly released from capsaicin-sensitive afferents) plays an important role in the capsaicin-evoked response. No evidence has been found for an involvement of PPADS-sensitive P(2) purinoceptors in the response to capsaicin or for a stimulation or inhibition of capsaicin-sensitive receptors by anandamide in the human sigmoid colon.

PACAP-(6-38) inhibits the effects of vasoactive intestinal polypeptide, but not PACAP, on the small intestinal circular muscle.

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating peptide-(1-38) (PACAP) have been found to stimulate distension-induced peristaltic motility in the guinea-pig isolated small intestine. In this study, we tested whether the putative VIP/PACAP receptor antagonist PACAP-(6-38) counteracts the properistaltic effect of VIP and PACAP in isolated segments of the guinea-pig small intestine. VIP (100 nM) and PACAP (30 nM) had a stimulatory effect, i.e., lowered the peristaltic pressure threshold at which peristaltic waves were triggered and enhanced the frequency of peristaltic waves. PACAP-(6-38) (3 microM) was per se without effect on peristalsis but prevented or reversed the peristaltic motor stimulation caused by VIP, when it was given before or after the agonist, respectively. PACAP-(6-38), however, failed to antagonize the properistaltic effect of PACAP. In ileal circular strips treated with tetrodotoxin (1 microM) and indomethacin (3 microM), spontaneous myogenic activity was inhibited by VIP (5-30 nM). This effect was significantly reduced by a pretreatment with PACAP-(6-38) (3 microM). A similar inhibition by PACAP-(1-38) (10-500 nM) was not influenced by the antagonist. It is concluded that PACAP-(6-38) is a VIP receptor antagonist, both in the peristaltic motor pathways and at the level of the circular muscle of the guinea-pig small intestine. The lack of a motor effect of PACAP-(6-38) on its own indicates that VIP acting on PACAP-(6-38)-sensitive receptors (located on neurons and/or the smooth muscle) is unlikely to participate in peristaltic motor regulation.

Inhibition of the NANC relaxation of the guinea-pig proximal colon longitudinal muscle by the purinoceptor antagonist PPADS, inhibition of nitric oxide synthase, but not by a PACAP/VIP antagonist.

The effects of the P(2)-purinoceptor antagonist pyridoxal-phosphate-6-azophenyl- 2('),4(')- disulphonic acid (PPADS), the nitric oxide (NO) synthase inhibitor N(G)-nitro- l -arginine (l -NOARG), the K(+)-channel blocker apamin, the pituitary adenylate cyclase activating peptide (PACAP) antagonist PACAP(6-38) and the sensory neuron-blocking drug capsaicin were examined on the non-adrenergic, non-cholinergic (NANC) relaxation evoked by electrical field stimulation in the longitudinal muscle of the guinea-pig proximal colon. Both PPADS (50 microm) and l -NOARG (100 microm) significantly inhibited the NANC relaxation. In the presence of l -NOARG, PPADS inhibited and apamin (100 nm) practically abolished the response. Capsaicin slightly but significantly enhanced the NANC relaxation at 10, but not at 1 Hz stimulation frequency. PACAP(6-38) (3 microm) had no effect on the NANC relaxation, although it abolished the relaxant effect of exogenous PACAP(1-27) (10 nm) and reduced that of exogenous vasoactive intestinal polypeptide (VIP, 30-100 nm) by about 60 %. PPADS (50 microm) inhibited the relaxant action of exogenous adenosine 5(')-triphosphate (ATP; 1 and 10 microm), the inhibition being stronger at 1 microm ATP. These data indicate that an exogenous P(2)-purinoceptor stimulant (possibly ATP) and NO are involved in the NANC relaxation of the guinea-pig colon. The 'non-nitrergic' apamin-sensitive component of the response might also include an unidentified transmitter. No evidence has been found for a mediating role of PACAP/VIP-like peptides.

Inhibitory effect of PACAP(6-38) on relaxations induced by PACAP, VIP and non-adrenergic, non-cholinergic nerve stimulation in the guinea-pig taenia caeci.

The effect of the pituitary adenylate cyclase activating polypeptide (PACAP) receptor antagonist PACAP(6-38) on the relaxant response to exogenous PACAP, vasoactive intestinal polypeptide (VIP) and nonadrenergic, non-cholinergic (NANC) nerve stimulation was tested in the guinea-pig taenia caeci, in the presence of atropine (10(-6) M) and guanethidine (3x10(-6) M). PACAP(6-38) (3x10(-6) M) strongly inhibited sub-maximal relaxations evoked by exogenous PACAP (1-3x 10(-8) M) or VIP (10(-8) M), but not those due to isoprenaline (4-8x10(-8) M) or ATP (10(-6) M). PACAP(6-38) caused a small but significant (approximately 20%) inhibition of the NANC relaxation due to electrical field stimulation (1 Hz or 10 Hz for 20 s). At these frequencies PACAP(6-38) caused no inhibition of the NANC relaxation in the presence of the P2 purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; 5x10(-5) M), or PPADS plus the NO-synthase blocker NG-nitro-L-arginine (L-NOARG; 10(-4) M); in preparations pretreated with L-NOARG (10(-4) M) alone PACAP(6-38) retained its inhibitory effect. The PPADS- and L-NOARG-resistant NANC relaxation with 10 Hz electrical stimulation was blocked by apamin (10(-7) M); it was not significantly modified by the tachykinin receptor antagonist spantide (10(-5) M). Tachyphylaxis to PACAP(1-27) (10(-7) M for 10 min) strongly inhibited the relaxation due to PACAP(1-38) (1-3x10(-8) M) and reduced electrical stimulation-evoked relaxations by half. The putative VIP antagonist VIP(10-28) (10(-5) M) failed to significantly reduce the relaxant action of exogenous VIP (1-3x10(-8) M). Relaxation induced by PACAP(1-38) (1-2x10(-8) M) was not influenced by a mixture of PPADS (5x10(-5) M) and L-NOARG (10(-4) M). It is concluded that: (a) PACAP(6-38) is a VIP/PACAP antagonist in the guinea-pig taenia caeci; (b) a release of a VIP/PACAP-like substance from enteric nerves is involved in the NANC relaxation in this preparation, but its contribution is relatively small and seems to depend on the functional integrity of the PPADS-sensitive inhibitory mechanism; (c) the PPADS- plus L-NOARG-resistant NANC relaxation probably involves apamin-sensitive K+ channels.

Evidence for the involvement of ATP, but not of VIP/PACAP or nitric oxide, in the excitatory effect of capsaicin in the small intestine.

The contractile effect of capsaicin in the guinea-pig small intestine involves an activation of enteric cholinergic neurons. Our present data show that the P(2) purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 30 microM) significantly reduces the contractile response to capsaicin (2 microM) in the presence, but not in the absence, of the tachykinin receptor antagonists [O-Pro(9), (Spiro-gamma-lactam)Leu(10), Trp(11)]physalaemin (1-11) (GR 82334; 3 microM) and (S)-(N)-(1-(3-(1-benzoyl-3-(3, 4-dichlorophenyl)piperidin-3-yl)propyl)-4-phenylpiperidine-4-yl)-N -methylacetamide (SR 142804: 100 nM) (for blocking tachykinin NK1 and NK3 receptors, respectively). PPADS (30 microM) fails to influence submaximal cholinergic contractions evoked by cholecystokinin octapeptide (CCK-8; 2-3 nM) or senktide (1 nM), or the direct smooth muscle-contracting effect of histamine (100-200 nM). A higher concentration (300 microM) of PPADS is also without effect against the stimulatory action of cholecystokinin octapeptide. This means that PPADS can probably be safely used as a purinoceptor antagonist in intestinal preparations. The putative pituitary adenylate cyclase activating peptide (PACAP) receptor antagonist PACAP-(6-38) (3 microM) significantly reduces the contractile effect of PACAP-(1-38) (10 nM) and abolishes that of vasoactive intestinal polypeptide (VIP; 10 nM). PACAP-(6-38) (3 microM) fails to influence the effect of capsaicin (2 microM) both in the absence and in the presence of tachykinin receptor antagonists. The nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine (L-NOARG; 100 microM) also fails to inhibit the capsaicin-induced motor response. We conclude that an endogenous ligand of PPADS-sensitive P(2) purinoceptors (possibly ATP), but not a VIP/PACAP-like peptide or NO, is involved in the nontachykininergic activation of cholinergic neurons in the course of the capsaicin-induced contraction.