neuropeptide-y and 3-hydroxybenzylhydrazine

The effect of neuropeptide Y (NPY) on the basal and nerve stimulation-induced increase in norepinephrine synthesis was studied in the isolated and perfused mesenteric arterial bed of the rat. Tyrosine hydroxylation, the rate-limiting step in catecholamine (CA) biosynthesis, was assessed by measuring the accumulation of DOPA in the perfusate/superfusate overflow after perfusion of the mesenteric arterial bed with the decarboxylase inhibitor m-hydroxybenzyl hydralazine (NSD-1015). Treatment with NDS-1015 resulted in a time-dependent increase in DOPA production and nerve stimulation (8 Hz, supramaximal voltage, 2 ms duration) increased DOPA production even further. NPY 1 to 100 nM was observed to produce a concentration-dependent attenuation in both the basal and nerve stimulation-induced increase in DOPA formation. To come to an understanding of the NPY receptor subtype mediating the inhibition of CA synthesis, the rank order of potency of a series of NPY analogs with varying selectivity for NPY receptor subtypes including intestinal polypeptide (PYY), PYY 13-36, Leu36 Pro34 NPY, human pancreatic polypeptide (h-PP), and rat pancreatic polypeptide (r-PP) were determined. In addition, the effect of various selective NPY antagonists on the inhibitory effect of NPY was also examined. These included the Y1 antagonist BIB03304, the Y2 antagonist BIIE0246, and the Y5 antagonist CGP71683. The IC50's for NPY, PYY, PYY13-36, Leu31 Pro34 NPY, and hPP in inhibiting CA synthesis were 5, 7, 15, 30, and 33 nM respectively. rPP failed to inhibit CA synthesis. All 3 of the NPY antagonists produced attenuation of the NPY-induced inhibition of CA synthesis, but it took a combination of all 3 to completely block the effect of a maximal inhibitory concentration of NPY. These results demonstrate that NPY inhibits CA synthesis in the perfused mesenteric arterial bed and can do so by activation of a variety of receptors including the Y1, Y2, and Y5.

Topics: Animals; Aromatic Amino Acid Decarboxylase Inhibitors; Catecholamines; Dihydroxyphenylalanine; Dose-Response Relationship, Drug; Electric Stimulation; Hydrazines; Hydroxylation; In Vitro Techniques; Male; Mesenteric Arteries; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Receptors, Neuropeptide Y; Tyrosine

In PC12 rat pheochromocytoma cells differentiated with nerve growth factor (NGF), neuropeptide Y inhibited depolarization-stimulated catecholamine synthesis as determined by in situ measurement of 3,4-dihydroxyphenylalanine (DOPA) production in the presence of the decarboxylase inhibitor m-hydroxybenzylhydrazine (NSD-1015). The inhibition by neuropeptide Y was concentration-dependent and was prevented by pretreatment with pertussis toxin, suggesting the involvement of a GTP-binding protein of the Gi or Go subtype. The neuropeptide Y analog [Leu31,Pro34]neuropeptide Y also caused inhibition of DOPA production, but was less potent than neuropeptide Y itself, while peptide YY and neuropeptide Y-(13-36) had no significant effect. This pattern is most consistent with the involvement of the neuropeptide Y Y3 receptor subtype. In PC12 cells differentiated with dexamethasone, neuropeptide Y also caused a concentration-dependent inhibition of DOPA production, while peptide YY was again without effect. Neuropeptide Y had no effect on DOPA production in undifferentiated PC12 cells. These results indicate that neuropeptide Y can modulate catecholamine synthesis in addition to its modulatory effects on catecholamine release.

Topics: Adrenal Gland Neoplasms; Analysis of Variance; Animals; Anti-Inflammatory Agents, Non-Steroidal; Aromatic Amino Acid Decarboxylase Inhibitors; Cell Differentiation; Dexamethasone; Dihydroxyphenylalanine; Dose-Response Relationship, Drug; Gastrointestinal Hormones; GTP-Binding Proteins; Hydrazines; Nerve Growth Factors; Neuropeptide Y; PC12 Cells; Peptide Fragments; Peptide YY; Peptides; Pertussis Toxin; Pheochromocytoma; Rats; Structure-Activity Relationship; Virulence Factors, Bordetella

The objective of the study was to determine the role of neuropeptide Y (NPY) and biogenic amines on the onset of puberty in birds. Male broiler chicks were administered chronic intracerebroventricular (ICV) injections of 5 micrograms NPY which produced sexually precocious chicks, determined by advanced secondary sex characteristics. One or two weeks following the beginning of a series of NPY injections, the preoptic area (POA), bed nucleus of the pallial commissure (nCPa), paraventricular nucleus (PVN), and median eminence (ME) were analyzed for biogenic amines. Levels of L-dopa, the precursor of dopamine (DA) were increased within the ME of chicks that responded to treatments by showing advanced sexual maturation when an amino acid decarboxylase blocker was administered prior to sacrifice. The PVN of respondents showed several changes in biogenic amines, while the nCPa displayed a biogenic amine metabolite of unknown identity which was significantly lower in respondent chicks. In contrast to mammals, L-dopa was detectable within the nCPa, PVN, and ME regardless of whether an enzymatic blocker of amino acid decarboxylase was administered to chicks prior to sacrifice. Results suggest that increased brain levels of NPY and DA, the latter specifically occurring within the ME, are associated with the onset of puberty. Due to the several significant differences found in biogenic amino levels within the PVN of respondent chicks, this nucleus, similar to the ME may be a highly active and integrative neural structure during the onset of puberty in chicks.

Topics: Animals; Aromatic Amino Acid Decarboxylase Inhibitors; Biogenic Amines; Chickens; Diencephalon; Hydrazines; Injections, Intraventricular; Male; Neuropeptide Y; Sexual Maturation