Evaluation of Acute and Sub-Acute Toxicity of Aqueous Extracts of Artemisia afra Leaves on Brain, Heart and Suprarenal Glands in Swiss Albino Mice

Background

The majority of population rely on traditional medicine as a source of healthcare. Artemisia afra is a plant traditionally used for its medicinal values, including treatment of malaria in many parts of the world. Currently, it is also attracting attention because of a claim that a related species, Artemisia annua, is a remedy for the COVD-19 pandemic. The aim of the present study was to investigate toxic effects of A. afra on brain, heart and suprarenal glands in mice aged 8–12 weeks and weighing 25–30g.

Methods

Leaves of A.afra were collected from Bale National Park, dried under shade, crushed into powder and soaked in distilled water to yield aqueous extract for oral administration. For acute toxicity study, seven treated and one control groups, with 3 female mice each, were used. They were given a single dose of 200mg/kg, 700mg/kg, 1200mg/kg, 2200mg/kg, 3200mg/kg, 4200mg/kg or 5000mg/kg b/wt of the extract. For the sub-acute toxicity study, two treated and one control groups, with 5 female and 5 male mice each, were used. They were daily treated with 600mg/kg or 1800mg/kg b/wt of extract.

Results

LD₅₀ was found to be greater than 5000mg/kg indicating that the plant is relatively safe. In the sub-acute study, no signs of toxicity were observed in all treatment groups. On microscopic examination of the brain, heart and suprarenal glands no sign of cellular injury was observed.

Conclusion

The findings of this study suggest that the leaves extract of A. afra is relatively safe in mice.

Effect of 70% Ethanol Extract and its Solvent Fractions of Artemisia afra (Jacq. Ex Willd.) against Pentylenetetrazole-Induced Seizure in Mice

INTRODUCTION

Artemisia afra (Jacq. ex Willd.), commonly called African wormwood, is a highly aromatic perennial herb and a well-known medicinal plant, claimed to be effective and safe in the treatment of epilepsy. The whole-plant extract is traditionally used as an antiepileptic agent in Ethiopia. Aim of the Study. The aim of this study was, therefore, to evaluate the anticonvulsant effect of the hydroethanolic extract and solvent fractions of A. afra whole part in mice.

MATERIALS AND METHODS

The effects of A. afra hydroethanolic extract and its solvent fractions were evaluated against pentylenetetrazole- (PTZ-) induced convulsions in mice. The onset and duration of PTZ-induced convulsions were determined with hydroethanolic A. afra extract and its solvent fractions. Data were analyzed using a one-way analysis of variance (ANOVA) followed by post hoc Tukey's multiple comparisons test. p < 0.05 was considered statistically significant.

RESULTS

The hydroethanolic extract of A. afra, with all the three doses of 250, 500, and 1000 mg/kg, showed a significant delay (504.833 ± 62.835 ∗  s; p < 0.05 ∗ ; 551.833 ± 47.69 ∗∗  s; p < 0.01 ∗∗ ; and 808.333 ± 64.8 ∗∗∗ s; p < 0.001 ∗∗∗ , respectively) in the mean onset of convulsion and a decrease (17.000 ± 1.88 ∗∗∗  s, p < 0.05 ∗ ; 13.000 ± 1.8 ∗∗  s, p < 0.01 ∗∗ ; and 7.833 ± 1.07 ∗∗∗  s, p < 0.001, respectively) in the mean duration of convulsion against PTZ-induced convulsion in a dose-dependent manner compared to the control (92.833 ± 13.006 s; 34.167 ± 3.683 s), and its anticonvulsant activity was significantly less compared to that of diazepam (1001.167 ± 68.430 s; 4.500 ± 0.619 s). The solvent fractions, however, did not show anticonvulsant activity against PTZ-induced convulsion.

CONCLUSION

Crude extract of A. afra has an anticonvulsant effect in mice. This might be attributed to the synergistic effects of two or more active ingredients present in the herb.

COVID-19 Pandemic: A Compressive Review on Gender, Herd Immunity, and Physiological Mechanisms

BACKGROUND

Researchers and scientists experienced the spread and aid recovery of the COVID-19 pandemic with a condition of great uncertainty. With limited understanding of SARS-CoV-2, current attempts at controlling its spread are focused on the suppressing approach (to reduce a sustained endogenous transmission) and the mitigating approach (to reduce the growth rate of the epidemic). On the one hand, while there has been no firm explanation, many governments have considered immunity passport and herd immunity for paths out of restrictive physical distancing measures imposed to control the spread of SARS-CoV-2 but were not successful.

PURPOSE OF REVIEW

Herein, we attempted to systematize the lessons and shreds of evidence related to the spectrum of illness, the physiological mechanisms of host susceptibility, herd immunity, immunity passport, gender disparities, and severe challenges and uncertainties posed by the COVID-19 pandemic. We hope that the insights provided in this review will help raise the effectiveness of the treatment policies and preventive measures required to end the pandemic.

RECENT FINDINGS

The use of immunity passports is suggested to certify an individual at low risk of acquiring or transmitting SARS-CoV-2. But, an individual might nevertheless carry the virus at similar levels and for a similar duration to those previously uninfected, with an unchanged potential for transmission. Vaccine-induced herd immunity is a complex issue inherent to a vaccine and the population receiving the vaccine. The central epidemiological questions about are as follows: what proportion of the population should be vaccinated to meet elimination (in a local program), eradication (in a global program) or a defined level of control? How is this affected by demographic factors (such as gender)? What is the best age at which to immunize? Besides, although age-dependent mortality risk is estimated to be higher for men and older people, such interpretation across gender, age groups, and countries, however, must be accepted with caution at present.

SUMMARY

COVID-19 has taught us that health is the basis of global wealth and international solidarity is an essential response and a superior approach to isolationism. Hence, we must be clear about what the alternatives are when evaluating the merits of different ways of tackling this pandemic both in the short term as well as in the long term.

The magnitude of anemia and associated factors among adult diabetic patients in Tertiary Teaching Hospital, Northern Ethiopia, 2019, cross-sectional study

Background

Patients with Diabetic Mellitus are at higher risk of different complications. Many previous studies show that anemia among diabetic patients is poorly diagnosed.

Objective

This study aimed to assess the magnitude and associated factors of anemia among adult diabetes patients having regular follow up at the diabetic clinic of Ayder Comprehensive Specialized Hospital, Tigray, 2018/19.

Methods

This study was conducted the Diabetic clinic of Ayder comprehensive specialized hospital, Tigray regional state, Northern Ethiopia from January to March 2019. A systematic random sampling technique was used to select study participants. About 5 ml of venous blood was collected by experienced laboratory technologists under a complete aseptic technique. Two ml of the venous blood was used for hemoglobin determination. And three ml of the venous blood was used without any anticoagulant for creatinine determination. The association of variables was assessed using bivariate and multivariable analysis in the logistic regression model with p-value, odds ratio, and 95% CI in the SPSS version 24 software.

Results

From a total of 262 diabetes patients, forty-seven (17.9%) were found to be anemic (6.7% males and 11.5% females). Among the related factors, residency (Adjusted Odds Ratio, 7.69, 95% CI, 2.060, 28.69, p = 0.002,), age of the patients (Adjusted Odds Ratio, 4.007, 95%CI, 1.53–10.51, p = 0.005,) and sex (Adjusted Odds Ratio, 3.434, 95% CI, 1.582, 7.458, p = 0.042,) were significantly associated with anemia.

Conclusion

According to this study, the magnitude of anemia is high among diabetic patients. Occupation of the participants, residency, HIV status, being female, and age was significantly associated with anemia.

Anemia in HIV/AIDS Patients on Antiretroviral Treatment at Ayder Specialized Hospital, Mekele, Ethiopia: A Case-Control Study

Background

Human immunodeficiency virus and anemia are the major public health problems in Sub-Sahara Africa. Untreated anemia is associated with rapid progression and poor prognosis of the disease in HIV. This study was aimed at determining the magnitude, severity and associated factors of anemia among HIV infected patients taking zidovudine and tenofovir-containing first-line HAART in Ayder Comprehensive Specialized Hospital, Mekele, Ethiopia.

Methods

A case-control study was conducted from February to August 2019 using both convenient and quota sampling methods. Anemia is defined as hemoglobin value below 13 g/dl for male and below 12 g/dl for female. Sociodemographic and clinical characteristics were assessed using a structured questionnaire, medical records, electronic weighing scale, adult height board, automated hematology analyzer (Sysmex XT-4000i), and Becton Dickinson’s FACS caliber flow cytometer. Descriptive statistics, tables, graphs, Student’s t-test and l logistic regression were used to analyze the data.

Results

About one-third (33.5%) of study participants were found to be anemic (ZDV: 20.3%; TDF: 13.2%, and p<0.05). Among these anemic cases, the majority was found to have mild, and the remaining was moderate types. The most common form was normocytic-normochromic anemia (46.5%). Cotrimoxazole prophylaxis, poor adherence, advanced AIDS stage at baseline and underweight at baseline were the factors associated with anemia in patients taking zidovudine-containing regimen (p<0.05). Advanced stage at baseline, cotrimoxazole prophylaxis, poor adherence status and lack of regular income were significantly associated with anemia in patients taking tenofovir-containing regimen (p<0.05).

Conclusion

We find that the prevalence of anemia was significantly higher among patients taking ZDV-containing regimen. But different risk factors for anemia had been identified among ZDV-containing regimen, showing that appropriate follow-up, nutritional supplementation, continuous evaluation of patients on cotrimoxazole intake can reduce the risks of anemia in both types of regimens.

Changes in biochemical parameters by gender and time: Effect of short-term vegan diet adherence

Background

Vegetarian diets adapted for various reasons that may include religious, ethical, and health considerations have reasonable health benefits including weight loss, and favorable metabolic changes. However, studies that assessed health benefits associated with vegan diet practices during the Ethiopian Orthodox Christian (EOC) Lenten fasting remains limited. This study has, therefore, assessed how short-term vegan diet associated with metabolic traits, including weight, body mass index (BMI), circumference, blood pressure, total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), through longitudinal cross-sectional study design.

Methods

Seventy-five subjects (34 females and 41 males) with a mean age of [+SD] 27.3 + 5.8 years (range, 18 and 35) took part in the study. The study followed three assessment sessions: at baseline, during the Lenten (week 7), and 7 weeks after the end of the Lenten (week 14). An automatic chemistry analyzer (Mindray, BE-2000, China) used for lipid profile analysis. We used paired sample t-test in pre and post-performance and repeated measures ANOVA with Bonferroni post hoc adjustment between time points. The statistical significance was set at p < 0.05.

Results

The EOC fasting with vegan diet induced significantly lower blood pressure, weight, BMI, TC, HDL-C, LDL-C, and TC: HDL-C ratios, during Lenten (that is vegan diet consumption), but a regain noted in these parameters 7-weeks after Lenten (that is omnivore diet). On gender differences, vegan diet associated with significantly lower blood pressure, TC, and LDL-C in females compared with age-matched male counterparts. Some methodological limitations of this study are discussed with particular reference to lack of a randomized control group and self-reported data that limit this study in establishing a causal relationship through observed associations.

Conclusions

Vegan diet consumption even for short period corroborate ideal metabolic traits, with more favorable changes noted in women than age-matched men counterparts. These findings might help to define vegetarian diets as part of religious fasting (beyond its spiritual goals) as a non-pharmacological prescription in different populations, and our findings add to growing evidence in these subjects.

Rewarding Effect of Catha edulis (Khat) and the Sex Differences to the Responses in Swiss Albino Mice

Background

Burden of substance abuse is becoming a worldwide problem. One of the psychostimulant plants widely consumed in Ethiopia and other East African countries is Catha edulis Forsk (khat). Most of the users claim that its stimulatory effect is the determinant factor that makes them use. However, its rewarding and reinforcing potential and variation between sexes have not been investigated. This study was, therefore, designed to measure the rewarding effect of khat extract (ke) in the addiction mice model of both sexes.

Materials and Methods

Forty-eight Swiss albino mice of both sexes (age 6–7 weeks) weighing 21–33 gm were used. The mice were conditioned to ke (100 mg/kg, 200 mg/kg and 300 mg/kg b.w). The control group was conditioned to tween 80 (2%, v/v) in distilled water. The reinforcing effect of khat was evaluated using the conditioned place preference paradigm. The classical pairing to the extract was made using the place conditioning box. Post-conditioning tests have been conducted four times and the average values were taken for analysis using SPSS version 21.0.

Results

Time spent in the khat-paired compartment was significantly higher for mice conditioned to ke 200 mg/kg (p<0.05) and ke 300 mg/kg (p<0.001). The rewarding effect of khat was strong in females at a higher dose when compared to the same sex of mice conditioned to the vehicle (p<0.001) or male mice conditioned to the same dose of khat extract (p<0.05). Repeated administration increased khat rewarding sensitization at all doses. Though the crude khat extract did not affect the food consumption and total body weight, water consumption was significantly less in mice received ke 100 mg/kg (p<0.01), where it was significantly higher in mice received ke 300 mg/kg (p<0.01). Sniffing (p<0.05) and climbing (p<0.05) psychomotor activities of mice were also affected by the crude khat extract.

Conclusion

Mice showed place conditioning to khat extract, and the response was significantly higher in female mice. The crude khat extract did not affect food consumption and total body weight. The mechanisms behind the rewarding response of khat extract and sexual differences should be investigated.

Hydride generation coupled with thioglycolic acid coated gold nanoparticles as simple and sensitive headspace colorimetric assay for visual detection of Sb(III)

Antimony (Sb) is a toxic element which causes different health problems including cardiac problems and lung cancer in humans, and its levels in surface water can be noticeably increased to 100 μg/L typically in the proximity of anthropogenic sources. Thus, besides instrumental techniques, it is of great significance to develop a simple, sensitive and selective analytical method for direct analysis of Sb(III) at trace level without the need of any expensive and/or complicated instrumentations and sample preparation processes. Herein, a simple and sensitive headspace colorimetric assay was developed for the detection of Sb(III) by hydride generation coupled with thioglycolic acid functionalized gold nanoparticles (TGA-AuNPs). Sb(III) in the 30 mL sample solution was converted into its volatile form (SbH₃) through hydride generation reaction and headspace extracted into 100 μL chromogenic reagent, which contains methanol as extractant and TGA-AuNPs as nanosensors, leading to aggregation of TGA-AuNPs and therefore a red-to-blue color change. Parameters influencing the chromogenic and hydride generation reactions were optimized. Addition of 300 μM ethylenediamine tetraacetic acid (EDTA) as masking agent largely suppressed the inferences from mercury and arsenic. The proposed method can tolerate at least 10-fold As(III) and 100-fold other metal ions including Hg(II). The detection limits were 6.0 and 1.2 μg/L Sb(III) by naked-eye and UV-Vis spectrometer, respectively, which meet the maximum admissible level in drinking water (6 μg/L) set by the United States Environmental Protection Agency. The feasibility of the proposed method was demonstrated by rapid detection of Sb(III) in river water, lake water, ground water and sea water samples by naked-eye at a spiking level of 6 μg/L Sb(III).

Antihypertensive activity of 80% methanol seed extract of Calpurnia aurea (Ait.) Benth. subsp. aurea (Fabaceae) is mediated through calcium antagonism induced vasodilation

ETHNOPHARMACOLOGICAL RELEVANCE

Calpurnia aurea (Ait.) Benth. subsp. aurea (CASA) (Fabaceae) seeds are used to treat hypertension in Ethiopian folklore medicine, particularly by Shinasha, Agew-awi and Amhara people in northwest Ethiopia. However, the claim has so far not been substantiated scientifically.

AIM OF THE STUDY

The study was conducted to evaluate the antihypertensive activity of 80% methanol extract of CASA in animal model of hypertension as well as its vasorelaxant effect and possible underlying mechanisms in isolated guinea pig aorta.

MATERIAL AND METHODS

Hypotensive and antihypertensive effect of CASA extract was determined in vivo through the intravenous (iv) route in normotensive and hypertensive anesthetized rats using 2-kidney-1-clip (2K1C) rat model. Ex vivo, guinea pig thoracic aortic rings were isolated and suspended in organ bath, and the vasodepressor effects as well as the mechanism of action of the extract were studied by means of isometric tension recording experiments.

RESULTS

The blood pressure fell dose-dependently and significantly in renal hypertensive and normotensive rats following i.v. administration, suggesting that the hydroalcoholic extract possesses hypotensive and antihypertensive effects. The extract also caused a dose-dependent relaxation of aorta pre-contracted with KCl at a concentration of 5-250mg/L, with a maximum relaxation of 92.1% achieved at 250mg/L. The relaxation mechanism was found to be independent of the muscarinic receptors, histamine receptors, ATP dependent K(+) channels, cyclooxygenase enzymes, cGMP/NO pathway and the endothelium system. The extract caused rightward shift of the Ca(++) dose-response curves, similar to that caused by verapamil, indicating that it produced vasorelaxation by inhibiting extracellular Ca(2+) influx.

CONCLUSIONS

The findings demonstrate that the plant is endowed with antihypertensive effect, providing evidence for its traditional use. The effect may be, at least in part, due to dilation of blood vessels through blockage of Ca(2+) channels.

In vivo and in vitro hypotensive effect of aqueous extract of Moringa stenopetala

BACKGROUND

Moringa stenopetala, Baker f. (Moringaceae) is used for food and medicine in Southern Ethiopia.

OBJECTIVE

To substantiate the hypotensive effect of M. stenopetala in vivo and in vitro.

METHODS

An in vivo experiment was carried out on male guinea pigs anaesthetized with pentobarbital. The arterial blood pressure was recorded from a carotid artery filled with heparinized saline via an arterial cannula connected to a pressure transducer. For the in vitro experiment the descending thoracic aorta was removed and kept moistened in Krebs-Henseleit solution and then mounted in a 20ml tissue bath maintained at 37°C and bubbled with a mixture of 95% oxygen and 5% carbon dioxide.

RESULTS

Crude aqueous leaf extract of M. stenopetala caused significant fall in systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial blood pressure (MABP) at doses of 10, 20, 30 and 40 mg/kg in normotensive anaesthetized guinea pigs (n = 12). The effect might have been mediated by non-autonomic nervous system as the effect is not altered by atropine and propranolol. The extract also caused significant dose and time dependent inhibition of K(+) induced contraction on guinea pig aorta.

CONCLUSION

M.stenopetala has blood pressure lowering effect substantiating the use of the plant in traditional medicine.

Receptor-mediated activation of gastric vagal afferents by glucagon-like peptide-1 in the rat

The vagus nerve plays a role in mediating effects of the two glucagon-like peptides GLP-1 and GLP-2 on gastrointestinal growth, functions and eating behaviour. To obtain electrophysiological and molecular evidence for the contribution of afferent pathways in chemoreception from the gastrointestinal tract, afferent mass activity in the ventral gastric branch of the vagus nerve and gene expression of GLP-1 receptors and GLP-2 receptors in the nodose ganglion were examined in Sprague-Dawley rats. Intravenous administration of GLP-1 (30-1000 pmol kg(-1)), reaching high physiological plasma concentrations, increased vagal afferent mass activity peaking (13-52% above basal level, P < 0.05) 3-5 min after injection. Repeated administration of GLP-1 (1000 pmol kg(-1); five times, 15 min intervals) elicited similar responses. Pretreatment with GLP-1 receptor antagonist exendin(9-39)amide (500 pmol kg(-1)) abolished the GLP-1 response to doses 30-300 pmol kg(-1) but had no effect on the vagal response to gastric distension. For comparison, GLP-2 (1000 pmol kg(-1)) had no effect on vagal afferent activity. Vagal chemoreception of GLP-1 is supported by expression of the GLP-1 receptor gene in the nodose ganglion. However, the GLP-2 receptor was also expressed. To conclude, our results show that peripherally administered GLP-1, differently from GLP-2, activates vagal afferents, with no evidence of desensitisation. The GLP-1 effect was blocked by exendin(9-39)amide, suggesting that GLP-1 receptors on vagal afferent nerves mediate sensory input from the gastrointestinal tract or pancreas; either directly or indirectly via the release of another mediator. GLP-2 receptors appear not be functionally expressed on vagal afferents.

The inhibitory mechanism of GLP-1, but not glucagon, on fasted gut motility is dependent on the L-arginine/nitric oxide pathway

Effects of glucagon-like peptide-1 (GLP-1) and glucagon on fasted gut motility in conscious rats were investigated as regards dependence on nitric oxide (NO). Small bowel motility was studied by electromyography and a jugular vein catheter was implanted for administration of drugs. GLP-1 (5-40 pmol x kg(-1) x min(-1)) prolonged the cycle length and abolished phase III of the migrating myoelectric complex (MMC) (P<0.01). Low doses of GLP-1 did not affect duration, propagation velocity or calculated length of phase III. At 1 mg x kg(-1) N(omega)-nitro-L-arginine (L-NNA) blocked the GLP-1 response up to a dose of 10 pmol x kg(-1) x min(-1) (P<0.05), while higher doses were able to overcome L-NNA-induced disinhibition of the GLP-1 response (P<0.05). Similarly, L-arginine at 300 mg x kg(-1) prevented L-NNA-induced disinhibition of the GLP-1 response (P<0.05). Glucagon (200-1000 pmol x kg(-1) x min(-1)) prolonged the cycle length and abolished phase III of MMC (P<0.01) independent of NO. Again, low doses of glucagon did not affect duration, propagation velocity or calculated length of phase III. In conclusion, inhibition of fasted motility by GLP-1 at low doses is dependent on NO, while high doses of GLP-1 and glucagon exert effects on motility independently from NO.

Glucagon-like peptide-1 retards gastric emptying and small bowel transit in the rat: effect mediated through central or enteric nervous mechanisms

This study investigated effects of glucagon-like peptide-1(7-36)amide (GLP-1) on gastric emptying, small intestinal transit, and contractility of smooth muscle strips in rats. GLP-1 at doses of 10 and 20 pmol/kg/min administered intravenously dose-dependently retarded transit of the small intestine (P < 0.001), while only the higher dose of 20 pmol/kg/min retarded gastric emptying (P < 0.01). GLP-1 at concentrations up to 10(-4) M did not affect the basal tone or contractility of the gastrointestinal muscle strips that were stimulated with electric field stimulation or acetylcholine. Our results demonstrate that small intestinal transit seems more sensitive than gastric emptying to inhibition by GLP-1 at physiologic levels in plasma. Furthermore, this inhibition appears to be mediated through central mechanisms rather than through peripheral actions. Thus, GLP-1 is suggested to inhibit gastric emptying and small intestinal transit through an indirect effect via central or enteric nervous mechanisms.

Glucagon-like peptide-1 retards gastric emptying and small bowel transit in the rat: effect mediated through central or enteric nervous mechanisms

This study investigated effects of glucagon-like peptide-1(7-36)amide (GLP-1) on gastric emptying, small intestinal transit, and contractility of smooth muscle strips in rats. GLP-1 at doses of 10 and 20 pmol/kg/min administered intravenously dose-dependently retarded transit of the small intestine (P < 0.001), while only the higher dose of 20 pmol/kg/min retarded gastric emptying (P < 0.01). GLP-1 at concentrations up to 10(-4) M did not affect the basal tone or contractility of the gastrointestinal muscle strips that were stimulated with electric field stimulation or acetylcholine. Our results demonstrate that small intestinal transit seems more sensitive than gastric emptying to inhibition by GLP-1 at physiologic levels in plasma. Furthermore, this inhibition appears to be mediated through central mechanisms rather than through peripheral actions. Thus, GLP-1 is suggested to inhibit gastric emptying and small intestinal transit through an indirect effect via central or enteric nervous mechanisms.

Inhibitory effect of glucagon-like peptide-1 on small bowel motility. Fasting but not fed motility inhibited via nitric oxide independently of insulin and somatostatin

Effects of glucagon-like peptide-1 (GLP-1)(7-36)amide on fasted and fed motility in the rat small intestine were investigated in relation to its dependence on nitric oxide (NO), insulin, and somatostatin. Small bowel electromyography was performed using bipolar electrodes implanted 15, 25, and 35 cm distal to pylorus, and transit was studied with a radioactive marker. In the fasted state, GLP-1 (5-20 pmol kg-1min-1), reaching physiological plasma levels, prolonged the migrating myoelectric complex (MMC) cycle length along with slowed transit. This effect was antagonized by exendin(9-39)amide. The NO synthase inhibitor Nomega-nitro- L-arginine (L-NNA) also blocked the response to GLP-1, whereas L-arginine restored the response. Insulin (80-200 pmol kg-1min-1) induced irregular spiking, whereas somatostatin (100-500 pmol kg-1min-1) increased the MMC cycle length, independently of NO. In the fed state, GLP-1 (20-40 pmol kg-1min-1) reduced motility, an inhibition unaffected by L-NNA, whereas motility was stimulated by exendin(9-39)amide. Infusion of GLP-1 (20-100 pmol kg-1min-1) did not affect plasma insulin, but somatostatin was increased. In conclusion, GLP-1 seems to inhibit small bowel motility directly via the GLP-1 receptor. Inhibition of fasting motility is dependent of NO and not mediated via insulin or somatostatin, whereas inhibition of fed motility is independent of NO.

Contractile responses of rat duodenum caused by transmural nerve stimulation: interaction between tachykininergic and cholinergic mechanisms

We have studied the importance of tachykinins and acetylcholine for motor stimulation of the rat duodenum in vitro. Contractions induced by transmural nerve stimulation and tachykinin receptor agonists selective for NK1, NK2 and NK3 receptors were used in combination with a neurokinin (NK)2 receptor antagonist, MEN 10,627, and atropine as a muscarinic receptor antagonist. Transmural nerve stimulation in the range 0.5-32 Hz caused frequency-dependent contractions. MEN 10,627 (10(-8), 10(-7) and 10(-6) M) dose-dependently reduced the contractile frequency-response curve (P < 0.01-0.001). Addition of atropine (10(-8) M) completely inhibited the response to transmural nerve stimulation (P < 0.001). As control, atropine alone reduced this response only by about 65%. Of the tachykinin analogues, [beta-AlaB]-neurokinin A(4-10) selective for NK2 receptors caused concentration-dependent contractions with high potency (pD2 8.01) and high efficacy, while substance P methyl ester acting on NK1 receptors had lower potency (pD2 7.94) and low efficacy, and senktide acting on NK3 receptors had a low potency (pD2 7.52) but high efficacy. With increasing concentrations of MEN 10,627 the response to [beta-AlaB]-neurokinin A(4-10) was markedly reduced (P < 0.01), while responses to substance P methyl ester and senktide were only slightly affected. Our results indicate that the physiological contractile responses of the rat duodenum are co-mediated by acetylcholine and tachykinins, for which NK2 receptors seem to be most important.