Inhibitory effects of neuropeptide Y on sympathetic neurotransmission in the rabbit iris-ciliary body.
Neuropeptide Y (NPY, 1-300 nM) mediated a concentration-dependent inhibition of field stimulation-evoked [3H]norepinephrine (NE) overflow from the isolated, superfused rabbit iris-ciliary body. At equimolar concentrations (100 nM), the homologous neuropeptide peptide YY (PYY) mimicked the effects of NPY, whereas pancreatic polypeptide (PP) and the C-terminal fragment of NPY did not modify [3H]NE release. NPY-induced inhibition of [3H]NE release was unaffected by pretreatment of tissues with atropine (100 nM) plus yohimbine (100 nM) and was non-additive with the maximal prejunctional effects of carbamycholine or clonidine, indicating that NPY acts independently of prejunctional muscarinic or alpha 2-adrenergic receptor activity to reduce [3H]NE overflow. It is concluded that NPY is a specific, potent modulator of adrenergic neurosecretion in the rabbit iris-ciliary body. These findings confirm the role of NPY as a co-transmitter at ocular sympathetic neuroeffector junctions, either mimicking or augmenting the actions of endogenously released norepinephrine.
Ohia
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Dept. of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Ky. Lions Eye Research Institute 40292-1511.
Jumblatt
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D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002924:Ciliary Body / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D003000:Clonidine / Q000494:pharmacology; D004347:Drug Interactions; D005260:Female; D007498:Iris / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D008297:Male; D009478:Neuropeptide Y / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D010191:Pancreatic Polypeptide / Q000494:pharmacology; D019894:Peptide YY; D010455:Peptides / Q000494:pharmacology; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D009478:Neuropeptide Y; D010455:Peptides; D019894:Peptide YY; D015016:Yohimbine; D010191:Pancreatic Polypeptide; D001285:Atropine; D002217:Carbachol; D003000:Clonidine; D009638:Norepinephrine