neuropeptide-y and Myocardial-Ischemia

The seriousness of scorpion envenomation results essentially from left cardiac function with pulmonary oedema and/or a state of shock. Adrenergic myocarditis, toxic myocarditis and myocardial ischemia are the 3 mechanisms that explain the cardiac dysfunction. Myocardial ischemia is not only due to the release of catecolamines but also the effect of the cytokines and/or neuropeptide Y on the coronary vessels. The cardiac damage can be due or enhanced by the depressive effect of the cytokines on the myocardial cells. The frequently observed hyperglycaemia only enhances the state of the already damaged myocardium.

Topics: Acidosis; Animals; beta-Thromboglobulin; Blood Platelets; Catecholamines; Cytokines; Endothelin-1; Humans; Hyperglycemia; Myocardial Ischemia; Myocarditis; Myocardium; Neuropeptide Y; Pulmonary Edema; Scorpion Stings; Scorpion Venoms; Scorpions; Shock, Cardiogenic; Stress, Physiological

Sympathetic nerve activation often accompanies tissue ischemia, which in turn stimulates angiogenesis, but whether the nerves regulate vascular functions beyond vasoconstriction (i.e., by promoting new vessel formation) has never been established. Neuropeptide Y (NPY) is a sympathetic cotransmitter preferentially released during intense or prolonged stress, which causes vasoconstriction and vascular smooth muscle cell proliferation by activating multiple Gi/o-coupled receptors, Y1 and Y5. At nonvasoconstrictive concentrations and through non-Y1 receptors, NPY also stimulates endothelial cell adhesion to matrix, migration, proliferation, capillary tube formation on matrigel, and aortic sprouting. Recent studies also indicate that NPY and its non-Y1 receptors exert powerful angiogenic effects in peripheral limb ischemia, promising a new way of treatment for revascularization of ischemic tissues.

Topics: Animals; Evidence-Based Medicine; Humans; Muscle, Smooth, Vascular; Myocardial Ischemia; Neovascularization, Pathologic; Neuropeptide Y; Sympathetic Nervous System

Acute myocardial infarction (AMI) is considered a major cause of death and disability. Myocardial perfusion scintigraphy (MPS) as a non-invasive diagnostic imaging procedure and certain biomarkers associated with myocardial ischemia (ISCH), such as ischemia-modified albumin (IMA), neuropeptide Y (NPY), N-terminal pro b-type natriuretic peptide (NT-proBNP), and high-sensitivity troponin T (hsTnT) could probably aid in the detection of myocardial infarction.. Between December 2011 and June 2012, we prospectively analyzed patients who underwent a MPS study with the clinical question of myocardial ISCH. An exercise test was performed along with a MPS. Blood was drawn from the patients before exercise and the within 3 minutes from achieving maximum load and was analyzed for the aforementioned biomarkers.. A total of 71 patients (56 men and 15 women) were enrolled with a mean age of 61 ± 12 years. Twenty-six patients (36.6%) showed reduced uptake on stress MPS images that normalized at rest, a finding consistent with ISCH. Between ISCH and non-ISCH groups, only hsTnT levels showed a significant difference with the highest levels pertaining to the former group both before (0.0075 ng/ml vs 0.0050 ng/ml, P = 0.023) and after stress exercise (0.0085 vs 0.0050, P = 0.015). The most prominent differences were seen in higher stages of the Bruce protocol (stress duration > 9.05 minutes - P < 0.017). None of the IMA, NPY, and NP-pro BNP showed significant differences in time between the two groups.. Although IMA, NPY, and NT-pro BNP may not detect minor ischemic myocardial insults, serum hsTnT holds a greater ability of detecting not only myocardial infarction but also less severe ischemia. Further studies with larger cohorts of patients are warranted in order to better define the role of hsTnT as a screening tool for myocardial ischemia.

Topics: Aged; Area Under Curve; Biomarkers; Exercise; Female; Humans; Male; Middle Aged; Myocardial Infarction; Myocardial Ischemia; Natriuretic Peptide, Brain; Neuropeptide Y; Peptide Fragments; Probability; Prospective Studies; Sensitivity and Specificity; Serum Albumin, Human; Troponin T

While the angiogenic effects of Neuropeptide Y (NPY) in myocardial ischemia and hypercholesterolemia have been studied, its effects on altering oxidative stress, fibrosis and cell death are not known. We hypothesized that local infiltration of NPY in a swine model of chronic myocardial ischemia and hypercholesterolemia will induce nerve growth and cell survival, while reducing oxidative stress and fibrosis. Yorkshire mini-swine (n=15) were fed a high cholesterol diet for 5 weeks. Three weeks after surgical induction of focal myocardial ischemia, an osmotic pump was implanted, which delivered NPY (n=8, high cholesterol treated, HCT) or the vehicle (n=7, high cholesterol control, HCC) for 5 weeks. Then myocardium was harvested for analysis. Assessment of myocardial function and perfusion was made the last intervention. Immunoblotting demonstrated significantly decreased levels of MMP-9 (p=0.001) and TGF-β (p=0.05) and significantly increased levels of Ang-1 (p=0.002), MnSOD (p=0.006) and NGF (p=0.01) in HCT. Immunohistochemistry results revealed significantly decreased TUNEL staining (p=0.005) and GLUT4 translocation (p=0.004) in HCT. The functional data showed significantly improved blood flow reserve (p=0.02) and improved diastolic function -dP/dt (p=0.009) in the treated animals. Local infiltration of NPY results in positive remodeling in ischemic myocardium in the setting of hypercholesterolemia. By initiating angio and neurogenesis, NPY infiltration improves blood flow reserve and restoration of fatty acid metabolism. The associated increased cell survival and decreased fibrosis result in improved myocardial diastolic function. NPY may have a potential therapeutic role in patients with hypercholesterolemia associated coronary artery disease.

Topics: Animals; Apoptosis; Cell Membrane; Cell Proliferation; Cell Survival; Chronic Disease; Coronary Angiography; Disease Models, Animal; Fatty Acids; Fibrosis; Gene Expression Regulation; Glucose Transporter Type 4; Heart Ventricles; Hypercholesterolemia; Hypertrophy; Male; Myocardial Ischemia; Myocytes, Cardiac; Neovascularization, Pathologic; Neuropeptide Y; Oxidative Stress; Swine

Pharmacologically induced angiogenesis could be a promising option in clinical situations with diffuse inoperable coronary artery disease e.g. metabolic syndrome and diabetes mellitus. The failure of focused cytokine, stem cell and gene therapies to achieve both perfusion and functional improvement in clinical trials suggests a more centralized control mechanism. Neuropeptide-Y (NPY) is one such natural neurotransmitter that is known to exert a multifaceted role during neo-angiogenesis and can possibly act as the central control. To date, the ability to harness the 'master switch' nature of NPY in a specific experimental model of metabolic syndrome and chronic myocardial ischemia has not been conclusively demonstrated. We hypothesized that infiltration of NPY into an area of chronic ischemia in a metabolic syndrome swine model would induce angiogenesis and improve myocardial perfusion and function. An osmotic pump was inserted three weeks after surgical induction of focal myocardial ischemia. We delivered either NPY or placebo for five weeks, after which the myocardial tissue was harvested for analysis. Assessments of myocardial perfusion and function were performed at each stage of the experiment. Local infiltration of NPY significantly improved collateral vessel formation, blood flow and myocardial function. We believe activation of NPY receptors may be a potential target therapy for patients with diffuse coronary artery disease.

Topics: Angiogenesis Inducing Agents; Animals; Coronary Angiography; Coronary Circulation; Disease Models, Animal; Hypercholesterolemia; Male; Myocardial Ischemia; Myocardium; Neuropeptide Y; Receptors, Neuropeptide Y; Swine

Cardiac function is regulated by a balance of sympathetic and parasympathetic transmission. Neuropeptide Y (NPY) and galanin (GAL) released from cardiac sympathetic neurons inhibits parasympathetic transmission in the heart. Sympathetic peptides may contribute to autonomic imbalance, which is characterized by increased sympathetic and decreased parasympathetic transmission and contributes to life threatening cardiovascular pathologies. Several gp130 cytokines are increased in the heart after myocardial infarction (MI), and these cytokines stimulate neuropeptide expression in sympathetic neurons. We used mice whose sympathetic neurons lack the gp130 receptor (gp130(DBH-Cre/lox) mice) to ask if cytokine activation of gp130 regulated neuropeptide expression in cardiac sympathetic nerves after MI. Myocardial infarction decreased NPY mRNA through a gp130 independent mechanism and increased VIP and PACAP mRNA via gp130, while GAL mRNA was unchanged. Immunohistochemistry revealed a gp130-dependent increase in PACAP38 in cells of the stellate ganglion after MI, and PACAP was detected in pre-ganglionic fibers of all genotypes and surgical groups. VIP was identified in a few sympathetic nerve fibers in all genotypes and surgical groups. GAL and PACAP38 were not detected in sham hearts, but peptide immunoreactivity was high in the infarct three days after MI. Surprisingly, peptides were abundant in cells that co-labeled with macrophage markers F4/80 and MAC2, but were not detected in sympathetic axons. PACAP protects cardiac myocytes from apoptosis, and GAL stimulates axon regeneration in addition to inhibiting parasympathetic transmission. Thus, these peptides may play an important role in cardiac and neuronal remodeling after ischemia-reperfusion.

Topics: Animals; Cytokine Receptor gp130; Galanin; Heart; Humans; Mice; Mice, Inbred C57BL; Mice, Knockout; Myocardial Ischemia; Myocardium; Neuropeptide Y; Neuropeptides; Pituitary Adenylate Cyclase-Activating Polypeptide; Reperfusion Injury; Sympathetic Nervous System; Vasoactive Intestinal Peptide

We investigated the role of neuropeptide Y (NPY), abundant in the myocardial sympathetic nervous system and endothelial cells, in angiogenesis during chronic myocardial ischemia. Adult male Yorkshire swine underwent ameroid constrictor placement on the proximal left circumflex coronary artery. After 3 weeks, an osmotic pump was placed to deliver either placebo (control, n=8) or NPY(3-36) (NPY, n=8) to the collateral dependent region. Five weeks after pump placement, after cardiac catheterization and hemodynamic assessment, the heart was harvested for analysis. NPY treated animals demonstrated increased mean arterial pressures and improved left ventricular function (+dP/dt). Cardiac catheterization demonstrated a significant increase in the blush score in the NPY group (p<0.001). Blood flow to the ischemic myocardium was not different between groups at rest or during ventricular pacing. Immunohistochemical double staining for CD-31 and smooth muscle actin demonstrated an increase in capillary and arteriole formation in NPY treated animals (p=0.02 and p<0.001). Immunoblotting showed a significant upregulation of DPPIV (p=0.009) and NPY receptors 1 (p=0.008), 2 (p=0.02) and 5 (p=0.03) in the NPY treated group. Additionally, there was significant upregulation of VEGF (p=0.04), eNOS (p=0.014), phospho-eNOS (ser1177) (p=0.02), and PDGF (p<0.001) in NPY treated group. The anti-angiogenic factors endostatin and angiostatin were significantly decreased in NPY treated animals (endostatin, p=0.03; angiostatin, p=0.04). Exogenous NPY(3-36) resulted in improved myocardial function and increased angiogenesis and arteriogenesis by stimulating growth factor, pro-angiogenic receptor upregulation, and decreasing anti-angiogenic expression, but did not increase blood flow to the ischemic myocardium. NPY may act as a good adjunct to primary agents of therapeutic angiogenesis.

Topics: Animals; Chronic Disease; Collateral Circulation; Coronary Angiography; Disease Models, Animal; Heart Function Tests; Immunoblotting; Immunohistochemistry; Microvessels; Models, Biological; Myocardial Ischemia; Neuropeptide Y; Perfusion; Sus scrofa

Cardiac ischemia-reperfusion alters sympathetic neurotransmission in the heart, but little is known about its effect on neuropeptide expression in sympathetic neurons. Ischemia followed by reperfusion induces the production of inflammatory cytokines in the heart, including interleukin-6 and cardiotrophin-1. These cytokines and related molecules inhibit the expression of neuropeptide Y (NPY), and stimulate the expression of vasoactive intestinal peptide (VIP), substance P (SubP), and galanin (GAL) in cultured sympathetic neurons. Therefore, we quantified NPY, VIP, SubP, and GAL mRNA in neurons of the stellate ganglia 1 week after ischemia-reperfusion to determine if neuropeptide expression was altered in cardiac sympathetic neurons. NPY, VIP, and SubP mRNAs were unchanged compared to unoperated control animals, but GAL mRNA was increased significantly. The increased GAL mRNA was not accompanied by elevated GAL peptide content in the stellate ganglia. Galanin content was increased significantly in the heart, however, indicating that elevated GAL mRNA led to increased peptide production. GAL content was increased in the left ventricle below the coronary artery ligation, but was not increased significantly in the atria or the base of the heart above the ligation. The buildup of GAL specifically in the damaged left ventricle is consistent with previous reports that GAL is transported to regenerating nerve endings after axon damage.

Topics: Animals; Coronary Vessels; Galanin; Gene Expression; Heart; Ligation; Male; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion; Neurons; Neuropeptide Y; Polymerase Chain Reaction; Rats; Rats, Sprague-Dawley; RNA, Messenger; Substance P; Sympathetic Nervous System; Vasoactive Intestinal Peptide

Topics: Biomarkers; Catecholamines; Coronary Vasospasm; Humans; Myocardial Ischemia; Myocardial Stunning; Neuropeptide Y; Stress, Psychological

The cardiovascular role of the neuropeptide Y Y1 receptors in-vivo and in-vitro in ischaemic heart failure was evaluated by using the novel neuropeptide Y Y1 selective antagonist BIBP 3226 (R-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-D-arginine-amid e). In pithed rats, incremental doses of BIBP 3226 inhibited the exogenous neuropeptide Y induced pressor response in a dose-related fashion and a bolus injection of BIBP 3226 (0.5 mg kg(-1)) significantly shifted the pressor response curve of exogenous neuropeptide Y to the right. The potentiation effect to exogenous neuropeptide Y on the pressor response to preganglionic sympathetic nerve stimulation in ischaemic heart failure rats as well as on the contractile response to noradrenaline in renal arteries in sham-operated animals were also inhibited by the neuropeptide Y Y1 antagonist. In conscious ischaemic heart failure rats, incremental doses of BIBP 3226 (0.125-1 mg kg(-1)) significantly reduced basal blood pressure and heart rate. Compared with sham-operated rats, neuropeptide Y by itself induced no contraction and no potentiation on noradrenaline elicited contraction in renal artery of the ischaemic heart failure rat. Furthermore, under in-vivo conditions, BIBP 3226 did not influence basal renal function or the response to exogenous neuropeptide Y on urinary volume, urinary sodium and urinary potassium. Our results demonstrate that although there is a downregulation of the Y1 receptors by ischaemic heart failure, Y1 receptors are still mainly involved in cardiovascular actions of exogenous neuropeptide Y and play a role in maintaining basal blood pressure and heart rate in ischaemic heart failure. However, our data do not imply any significant role of Y1 receptors on basal renal function in the ischaemic heart failure rat model.

Topics: Animals; Arginine; Blood Pressure; Cardiovascular System; Decerebrate State; Dose-Response Relationship, Drug; Heart Rate; Hemodynamics; In Vitro Techniques; Kidney; Male; Myocardial Ischemia; Neuropeptide Y; Norepinephrine; Potassium; Rats; Rats, Sprague-Dawley; Receptors, Neuropeptide Y; Renal Artery; Sodium

Topics: Angiotensin II; Animals; Endothelin-1; Extracellular Space; Heart; Hydroxyl Radical; Microdialysis; Myocardial Ischemia; Neuropeptide Y; Norepinephrine

An attempt to determine the consequences of prolonged ischemia on simultaneous regional changes in norepinephrine (NE) and neuropeptide Y (NPY) interstitial myocardial concentrations in a pig model in vivo was made. The aim of the authors was to investigate further the mechanism of the major NE release previously observed in perfused hearts preserved using a Langendorff technique. Regional myocardial ischemia was induced by ligation of the left anterior descending coronary artery (LAD) in ten anesthetized pigs. NE and NPY release was studied using interstitial microdialysis, a technique initially used to monitor neurotransmitter kinetics in brain dialysate samples. Four dialysis probes were implanted into the left ventricular wall of the beating heart. Two were implanted into the ischemic region (LAD) (for NE and NPY determinations, respectively) and the remaining two into the non-ischemic left circumflex coronary artery region (LCX). Dialysate NE and NPY concentrations, as indices of interstitial myocardial NE and NPY concentrations, were measured by HPLC and RLA, respectively. A slight but significant increase in NPY levels was observed in both territories (LAD: from 190 +/- 27 to 349 +/- 62 pmol/l, LCX: 146 +/- 30 to 257 +/- 52 pmol/l) suggesting moderate stimulation of cardiac sympathetic nerve activity following LAD occlusion. On the contrary, a marked but progressive increase in NE release was observed in the ischemic region (from 8.8 +/- 1.0 to 251.4 +/- 44.8 nmol/l), when NE levels in the non-ischemic region remained stable (from 10.3 +/- 2.1 to 11.0 +/- 1.9 nmol/l). These results demonstrate the utility of regional in-vivo myocardial NE and NPY monitoring using microdialysis. The strong and sustained NE accumulation occurring in the ischemic region is consistent with the hypothesis of a local non-exocytotic metabolic NE release in case of prolonged myocardial ischemia, when exocytotic release remain only minimal as attested by the slight increase in NPY observed.

Topics: Animals; Coronary Circulation; Coronary Disease; Hemodynamics; Myocardial Ischemia; Myocardium; Neuropeptide Y; Norepinephrine; Swine; Time Factors

Previous studies have demonstrated that alpha-trinositol (D-myo-inositol-1.2.6-trisphosphate; PP56) may act as a functional neuropeptide Y (NPY) inhibitor. Because NPY is known to be a potent vasoconstrictor, the effects of alpha-trinositol on renal function, vascular responses and the potentiating effects of NPY were investigated in rats with congestive heart failure (CHF) induced by ligation of the left coronary artery. Incremental doses of alpha-trinositol were given to conscious rats (bolus 2, 4 or 10 mg/kg i.v. followed by a 15-minute infusion 20, 40 and 100 mg/kg/h, respectively). Urinary volume, sodium and potassium excretions were significantly increased in both CHF and sham-operated control animals after alpha-trinositol administration compared with saline. Diuresis and natriuresis were observed also during co-administration of alpha-trinositol with NPY but not with norepinephrine (NE). In the pithed CHF rats, threshold doses of NPY potentiated the pressor effects of endothelin-1 (ET-1) and angiotensin II (AII), but not preganglionic nerve stimulation or phenylephrine administration. Alpha-trinositol antagonized both the pressor response to NPY and the potentiation by NPY of pressor responses to effects of ET-1 and AII. Our data show that alpha-trinositol exhibis diuretic and natriuretic effects as well as vascular antagonistic effects on NPY in normal and CHF rats. These effects of alpha-trinositol may be due to an interaction with NPY mediated antidiuresis and antinatriuresis.

Topics: Animals; Cardiovascular System; Diuresis; Heart Failure; Hemodynamics; Inositol Phosphates; Kidney; Male; Myocardial Ischemia; Natriuresis; Neuropeptide Y; Rats; Rats, Sprague-Dawley

In the present study, the cardiac outflow of endothelin, noradrenaline and neuropeptide Y was investigated in 13 patients undergoing first time coronary angioplasty (PTCA) due to stenosis of the left anterior descending coronary artery. During PTCA there was an increase in the coronary sinus levels of endothelin but no detectable changes in neuropeptide Y or noradrenaline concentrations. It is therefore concluded that endothelial damage rather than myocardial ischaemia is the cause of endothelin release during PTCA.

Topics: Angioplasty, Balloon, Coronary; Chromatography, High Pressure Liquid; Coronary Disease; Endothelins; Endothelium, Vascular; Humans; Myocardial Ischemia; Myocardium; Neuropeptide Y; Norepinephrine; Radioimmunoassay

The influence of single components of myocardial ischaemia, such as anoxia, substrate withdrawal, hyperkalemia and extracellular acidosis, on nicotine-induced norepinephrine (NE) release was investigated in the isolated perfused guinea-pig heart, in incubated human atrial tissue and in cultured bovine adrenal chromaffin cells (BCC). In normoxia, nicotine (1-1000 mumol/l) evoked a concentration-dependent release of NE (determined by high pressure liquid chromatography and electrochemical detection) from guinea-pig heart and human atrium. In contrast to selective anoxia (Po2 < 5 mmHg) or glucose withdrawal, respectively, anoxia in combination with glucose withdrawal (5-40 min) markedly potentiated nicotine-induced NE release both in guinea-pig heart and human atrium. The sensitization of cardiac sympathetic nerve endings to nicotine was characterized by a lower threshold concentration and an approximate two-fold increase of maximum NE release, peaking after 10 min of anoxia and glucose withdrawal. Cyanide intoxication (1 mmol/l) combined with glucose withdrawal resulted in a similar increase of nicotine-induced sympathetic transmitter release both in guinea-pig heart and human atrium. In contrast, the nicotine-induced (10 mumol/l) NE overflow was only slightly potentiated by 10 min of global ischaemia in guinea-pig heart. Both hyperkalemia ([K+] 16 mmol/l) and acidosis (pH 6.8-6.0) distinctly attenuated the stimulatory effect of nicotine in guinea-pig heart and human atrium under normoxic conditions. Consistent with an exocytotic release mechanism, NE release was dependent on the presence of extracellular calcium under all conditions tested. Furthermore, NE overflow from guinea-pig heart was accompanied by a release of the exocytosis marker neuropeptide Y (NPY; determined by radioimmunoassay). In BCC, nicotine (1-10 mumol/l) evoked a release of NE and NPY and a transient rise of [Ca2+]i (determined with fura-2) during normoxia which were both dependent on the presence of extracellular calcium. Both hyperkalemia and acidosis markedly reduced the exocytotic release of sympathetic transmitters and the corresponding [Ca2+]i-transients. These data demonstrate that nicotine-induced cardiac exocytotic NE release is markedly potentiated during short-term anoxia in combination with glucose withdrawal. In contrast, a brief period of ischaemia causes only a slight sensitization of cardiac sympathetic nerve endings to nicotine. This discrepancy may be due to an attentu

Topics: Adrenal Medulla; Animals; Calcium; Cattle; Cyanides; Dose-Response Relationship, Drug; Exocytosis; Fluorescent Dyes; Fura-2; Glucose; Guinea Pigs; Heart; Heart Atria; Hexamethonium; Humans; Hypoxia; In Vitro Techniques; Ischemia; Kinetics; Myocardial Ischemia; Myocardium; Neuropeptide Y; Nicotine; Norepinephrine

It was the aim of the present study to characterize the modulatory effect of muscarinic agonists on the overflow of norepinephrine and neuropeptide Y (NPY) from the in situ perfused guinea pig heart, induced by electrical stimulation of the left stellate ganglion (6 Hz, 5 V, 1 min). The muscarinic agonists oxotremorine (0.01-1 microM) and carbachol (0.1-10 microM) reduced norepinephrine and NPY overflow in a concentration-dependent manner to approximately 30% of control. The inhibitory effect of carbachol was antagonized by the unspecific muscarinic antagonist atropine (1 microM) but not by the nicotinic antagonist hexamethonium (100 microM). The M2-specific antagonist AF-DX-116BS was 25 times more potent than the M1-specific antagonist pirenzepine in antagonizing the inhibitory effect of carbachol [50% inhibitory concentration (IC50) = 0.2 microM for AF-DX-116BS; IC50 = 5.0 microM for pirenzepine]. These findings indicate that presynaptic muscarinic inhibition of stimulated norepinephrine and NPY release from the guinea pig heart is mediated mainly by activation of M2 receptors. As early as 2 min after stop-flow ischemia, the inhibitory effect of carbachol (10 microM) on the stimulation-evoked overflow of norepinephrine and NPY was lost. On reperfusion with oxygenated buffer after 10 min of stop-flow ischemia the inhibitory effect of carbachol (10 microM) on stimulation-induced norepinephrine and NPY overflow recovered within 3 min.

Topics: Animals; Atropine; Carbachol; Electric Stimulation; Guinea Pigs; Heart; Male; Myocardial Ischemia; Myocardial Reperfusion; Myocardium; Neuropeptide Y; Norepinephrine; Oxotremorine; Parasympatholytics; Pirenzepine; Receptors, Muscarinic

Topics: Animals; Coronary Circulation; Endothelins; Myocardial Ischemia; Myocardial Reperfusion; Neuropeptide Y; Norepinephrine; Swine; Time Factors

This study analyzed the effects of the neuropeptides, neurotensin, and human and porcine analogue, neuropeptide Y, in anesthetized open-chest dogs. The left anterior descending coronary artery was cannulated and perfused at constant pressure via a blood reservoir. Flow to the coronary cannula was measured by an electromagnetic flowmeter, and regional segment lengths were measured by sonomicrometer crystals. Neurotensin injected into the coronary cannula resulted in a dose-dependent increase of coronary flow; neuropeptide Y resulted in a decrease of coronary flow. Because these changes in flow were not explained by systemic hemodynamic effects or alterations in regional myocardial function, they were considered to be coronary dilatation or constriction. Coronary dilatation by neurotensin was not prevented by alpha- or beta-adrenoceptor blockade but was completely abolished by indomethacin or by lowering coronary perfusion pressure to 35 mmHg when depressed systolic segment shortening indicated myocardial ischemia. Coronary constriction by neuropeptides Y persisted at coronary perfusion pressure of 35 mmHg and was only attenuated by indomethacin. We conclude that in contrast to systemic effects, coronary vasodilatation by neurotensin is mediated by a prostanoid product of cyclooxygenase. Preactivation of the prostaglandin system may explain why neurotensin lost its coronary dilator effect during myocardial ischemia. Neuropeptide Y may elicit coronary constriction in addition to mechanic reduction of coronary flow resembling severe coronary stenosis.

Topics: Animals; Coronary Vessels; Dogs; Female; Heart; Hemodynamics; Indomethacin; Male; Myocardial Ischemia; Neuropeptide Y; Neurotensin; Prostaglandins; Regional Blood Flow