neuropeptide-y and 3-4-dihydroxyphenylglycol

Neurotransmitters and neuropeptides play important roles in the regulation of various neuroendocrine functions particularly feeding. The aim of this study was to investigate whether a functional interaction occurs among neuropeptide Y (NPY) at NPY Y1 receptors and noradrenaline overflow, as this may contribute to the regulation of appetite. The release of endogenous noradrenaline and its metabolite 3,4-dihydroxyphenylglycol (DHPG) were examined from hypothalamic and medullary prisms using the technique of in vitro superfusion and high performance liquid chromatography (HPLC) with coulometric detection. Noradrenaline and DHPG overflow was investigated at rest, in response to NPY (0.1 microM) and in response to the NPY Y1 receptor agonist, [Leu31,Pro34]NPY (0.1 microM). Perfusion with NPY and [Leu31,Pro34]NPY significantly reduced noradrenaline overflow from the hypothalamus and medulla. Perfusion with NPY and [Leu31,Pro34]NPY was without significant effect on hypothalamic DHPG overflow, while medullary DHPG overflow was significantly reduced by NPY and [Leu31,Pro34]NPY. Results from this study provide evidence of NPY Y1 receptor-mediated inhibition of noradrenaline release in the hypothalamus and medulla, further illustrating a complex interaction between neurotransmitters and neuropeptides within the rat brain.

Topics: Animals; Appetite; Brain; Chromatography, High Pressure Liquid; In Vitro Techniques; Male; Methoxyhydroxyphenylglycol; Neuropeptide Y; Norepinephrine; Rats; Rats, Sprague-Dawley; Receptors, Neuropeptide Y; Time Factors

The present experiments were carried out in isolated rat hearts perfused according to the Langendorff method at a constant pressure of 10 kPa. The aim was to measure norepinephrine (NE) overflow and its deaminated metabolite dihydroxyphenylglycol (DOPEG) by changing the composition of the buffer perfusing the heart to simulate hypoxia. When aerobic and glycolytic pathways were simultaneously reduced, NE and DOPEG overflow increased 711 and 145%, respectively, after 30 min, compared with control values of 0.45 +/- 0.06 and 0.66 +/- 0.7 ng.min-1.g-1 of heart (n = 8, p < 0.05). Whereas NE leakage decreased sharply after reoxygenation and glucose addition, DOPEG continued to increase up to 260% after 5 min of normal reperfusion. This mechanism was calcium independent and inhibited by 80% with desipramine (1 microM), confirming the role of the uptake I carrier, which reversed its normal transport direction. Neuropeptide Y, a marker of exocytotic release, did not increase in the perfusate with the progression of hypoxia, which supports the hypothesis of a nonexocytotic release. Tyramine (1 microM) significantly enhanced NE outflow by displacing the amine from its storage vesicles through a calcium-independent mechanism, indicating that a pool of NE was still available. In the presence of 1 microM clorgyline (a monoamine oxidase A inhibitor) but not deprenyl (a monoamine oxidase B inhibitor), NE outflow increased 934% and DOPEG only 40% at 30 min (n = 6, p < 0.05 versus control hearts).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Calcium; Coronary Circulation; Glucose; Heart; Hypoxia; In Vitro Techniques; Male; Methoxyhydroxyphenylglycol; Monoamine Oxidase; Monoamine Oxidase Inhibitors; Myocardium; Nerve Endings; Neuropeptide Y; Norepinephrine; Oxygen Consumption; Rats; Rats, Wistar; Sympathetic Nervous System

Forearm venous plasma concentrations of noradrenaline (NA), catecholamine metabolites (dihydroxyphenylglycol (DHPG), dihydroxyphenylacetic acid (DOPAC], dihydroxyphenylalanine (DOPA) and neuropeptide Y-like immunoreactivity (NPY-LI) were studied in 22 men aged 20 to 81 years in the supine position and after 30 min of standing posture. Venous plasma NA, DHPG and NPY-LI increased significantly in the standing position, whereas venous plasma DOPAC and venous plasma DOPA remained unchanged. Increments in venous plasma NA and DHPG upon standing up, as well as venous plasma NA in the standing-up position, increased significantly with age. The ratio between increments in venous plasma DHPG and venous plasma NA did not change with age. Venous plasma NPY-LI and venous plasma DOPA did not change with age, whereas venous plasma DOPAC decreased significantly. Changes in venous plasma NPY-LI were negatively correlated with changes in pulse pressure. These results confirm previous studies that sympathetic activity increases with age. The unchanged ratio between increments in venous plasma DHPG and venous plasma NA suggests that intra-neuronal deamination of recaptured NA is unchanged in the elderly. The lower basal venous plasma DOPAC concentration may suggest a reduced basal intraneuronal synthesis of NA in old age.

Topics: 3,4-Dihydroxyphenylacetic Acid; Adult; Aged; Aged, 80 and over; Aging; Blood Pressure; Catecholamines; Chromatography, High Pressure Liquid; Dihydroxyphenylalanine; Heart Rate; Humans; Male; Methoxyhydroxyphenylglycol; Middle Aged; Neuropeptide Y; Norepinephrine; Supination; Sympathetic Nervous System

Neuropeptide Y-like immunoreactivity (NPY-LI), norepinephrine (NE), and 3,4-dihydroxyphenylglycol (DOPEG), the intraneuronal metabolite of NE, were measured in superfusate before, during, and after electrical stimulation (ES) of nerves and in the tissue extract of dog pulmonary artery after in vitro superfusion. Vessels were stimulated at 12, 6, or 1 Hz. NE and DOPEG were quantified by high-performance liquid chromatography with electrochemical detection, NPY-LI by radioimmunoassay. The Krebs-Ringer superfusate was maintained at a partial pressure of oxygen of either 472, 100, 50, or 20 mmHg. Mean DOPEG efflux was 0.17, 0.15, 0.13, and 0.07 pmol/min during basal conditions and 0.73, 0.39, 0.30, and 0.15 pmol/min, respectively, during 12-Hz continuous stimulation using these four oxygen pressures. Stimulation-evoked efflux of NPY-LI was 1.5, 1.1, 0.3, and 0.2 fmol/min during 12-Hz stimulation. These studies provide evidence that the production and subsequent efflux of DOPEG into superfusate under resting conditions, during ES, and following ES are oxygen sensitive. Additionally, the efflux of NPY-LI from dog pulmonary artery resulting from high frequencies of ES is oxygen sensitive.

Topics: Animals; Dogs; Electric Stimulation; Female; In Vitro Techniques; Kinetics; Male; Methoxyhydroxyphenylglycol; Muscle, Smooth, Vascular; Neuropeptide Y; Norepinephrine; Oxygen; Partial Pressure; Perfusion; Pulmonary Artery

Neuropeptide Y (NPY), norepinephrine (NE), and 3,4-dihydroxyphenylglycol (DOPEG), the metabolite of NE that arises intraneuronally, were measured in superfusates before, during, and after nerve stimulation and in extracts of dog pulmonary artery after superfusion and electrical stimulation (ES) at 12, 6, and 1 Hz. NE and DOPEG were quantified by high-pressure liquid chromatography with electrochemical detection; peptides were quantified by radioimmunoassay. The rate of overflow of NPY, NE, and DOPEG into superfusate was measured over time. The overflow of DOPEG into superfusate during basal conditions was 3.0 times that of NE. Efflux of DOPEG and NPY increased during ES; peak effluxes were not reached, however, until after cessation of stimulation. NE efflux peaked during ES. Effluxes of NE, NPY, and DOPEG were frequency-dependent at 12 and 6 Hz; at 1 Hz efflux of only NE was greater than basal. Halothane decreased significantly the rates of NPY and DOPEG efflux during and after 12 Hz ES; DOPEG efflux evoked by 6 Hz stimulation was also decreased by halothane. The percentage of the total tissue content of NPY that overflowed was decreased by halothane. Halothane did not affect the molar ratios of NE:DOPEG or NE:NPY during basal conditions or ES. These studies provide evidence that halothane slows efflux of NPY that is released along with NE from dog pulmonary artery during high frequencies of stimulation. Halothane also reduces the metabolism of NE to DOPEG.

Topics: Animals; Depression, Chemical; Dogs; Electric Stimulation; Female; Halothane; In Vitro Techniques; Male; Methoxyhydroxyphenylglycol; Neuropeptide Y; Norepinephrine; Pulmonary Artery; Sympathetic Nervous System

The overflow of neuropeptide Y (NPY; radioimmunoassay), noradrenaline and dihydroxyphenylethylenglycol (DOPEG; high pressure liquid chromatography) from guinea-pig perfused hearts was investigated in relationship to exocytotic and nonexocytotic release mechanisms. Exocytotic release: Electrical stimulation of the left stellate ganglion (12 Hz; 1 min) evoked a calcium-dependent overflow of noradrenaline and NPY, that was accompanied by a minor and prolonged increase in DOPEG overflow. This increase in DOPEG overflow was attenuated by blockade of neuronal amine re-uptake. In the presence of calcium, a closely related co-release of noradrenaline and NPY was also observed during administration of veratridine (10 microM); it was completely prevented by tetrodotoxin (1 microM). Nonexocytotic release: In the absence of extracellular calcium, veratridine (30 microM) induced noradrenaline overflow only when combined with the reserpine-like agent Ro 4-1284 (10 microM). This overflow was accompanied by efflux of DOPEG, but not of NPY. Similarily, tyramine (1-100 microM) induced a calcium-independent concomitant overflow of both noradrenaline and DOPEG, but not of NPY. During anoxic and glucose-free perfusion a predominantly calcium-independent overflow of noradrenaline was observed; only in the presence of extracellular calcium was this overflow accompanied by a minor overflow of NPY. Noradrenaline overflow, induced by veratridine plus Ro 4-1284 (in the absence of calcium), by tyramine, or by anoxia, was suppressed by blockade of neuronal amine re-uptake, and was, therefore, mediated by reversed transmembrane amine transport by the neuronal uptake carrier. The results indicate that NPY is co-released with noradrenaline only during calcium-dependent exocytosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy-; Animals; Calcium; Chromatography, High Pressure Liquid; Electric Stimulation; Exocytosis; Ganglia, Sympathetic; Guinea Pigs; Hypoxia; Methoxyhydroxyphenylglycol; Myocardium; Neuropeptide Y; Norepinephrine; Radioimmunoassay; Tyramine; Veratridine

A method is described for separation and quantification of 3,4-dihydroxyphenylglycol (DO-PEG), norepinephrine (NE), dopamine (DA), vasoactive intestinal peptide (VIP), and neuropeptide Y (NPY) from single samples of tissue homogenate and from superfusate from in vitro dog blood vessel preparations using cartridges containing 0.4 g of octadecylsilane (Sep-Pak C-18). Samples were passed through the cartridge at pH 7.4. A step-gradient system was used to first selectively desorb the catechols (DOPEG, NE, DA) with a moderately polar eluent; subsequently VIP and NPY were eluted with 2.5 ml of a mixture of 1% trifluoroacetic acid, 80% acetonitrile. Five Sep-Pak catechol eluents were tested. Catechols were quantified by HPLC with electrochemical detection and peptides by radioimmunoassay. An HPLC solvent system is described which is particularly useful for chromatography of the more hydrophilic catechols DOPEG, 3,4-dihydroxymandelic acid, and 3,4-dihydroxyphenylalanine concurrently with catecholamines. For superfusion studies, sample cleanup time was reduced to about 4 min per sample by attachment of the cartridges directly to the bottom of the superfusion chamber. Superfusate was subsequently pulled through the cartridges immediately after they were passed over the tissue. Batches of 12 high-speed tissue supernates were processed through the method in about 30 min. The method was used to analyze DOPEG, NE, DA, VIP, and NPY in various rat and dog tissues. The values obtained were similar to values obtained previously by other methods. Because the catechols and peptides are separated from a single sample, the method has several advantages over those described previously; e.g., it is rapid, simple, and more sensitive.

Topics: Animals; Catecholamines; Chromatography, High Pressure Liquid; Dogs; Female; Glycols; Male; Methoxyhydroxyphenylglycol; Neuropeptide Y; Pulmonary Artery; Radioimmunoassay; Rats; Rats, Inbred Strains; Vasoactive Intestinal Peptide