Presynaptic and postsynaptic effects of neuropeptide Y in the rat pineal gland.
Neuropeptide Y is colocalized with noradrenaline in sympathetic fibers innervating the rat pineal gland. In this article we present a study of the effects and mechanisms of action of neuropeptide Y on the pineal noradrenergic transmission, the main input leading to the rhythmic secretion of melatonin. At the presynaptic level, neuropeptide Y inhibits by 45%, with an EC50 of 50 nM, the potassium-evoked noradrenaline release from pineal nerve endings. This neuropeptide Y inhibition occurs via the activation of pertussis toxin-sensitive G protein-coupled neuropeptide Y-Y2 receptors and is independent from, but additive to, the alpha 2-adrenergic inhibition of noradrenaline release. At the postsynaptic level, neuropeptide Y decreases by a maximum of 35%, with an EC50 of 5 nM, the beta-adrenergic induction of cyclic AMP elevation via the activation of neuropeptide Y-Y1 receptors. This moderate neuropeptide Y-induced inhibition of cyclic AMP accumulation, however, has no effect on the melatonin secretion induced by a beta-adrenergic stimulation. On the contrary, in the presence of 1 mM ascorbic acid, neuropeptide Y potentiates (up to threefold) the melatonin secretion. In conclusion, this study has demonstrated that neuropeptide Y modulates the noradrenergic transmission in the rat pineal gland at both presynaptic and postsynaptic levels, using different receptor subtypes and transduction pathways.
Simonneaux
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V
Neurobiologie des Fonctions Rythmiques et Saisonnières, URA-CNRS 1332, Université Louis Pasteur, Strasbourg, France.
Ouichou
A
A
Craft
C
C
Pévet
P
P
D000818:Animals; D001483:Base Sequence; D000242:Cyclic AMP / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000378:metabolism; D008969:Molecular Sequence Data; D009478:Neuropeptide Y / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D015345:Oligonucleotide Probes / Q000235:genetics; D010870:Pineal Gland / Q000187:drug effects* / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017476:Receptors, Neuropeptide Y / Q000235:genetics; D013569:Synapses / Q000187:drug effects*
D009478:Neuropeptide Y; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D017476:Receptors, Neuropeptide Y; D000242:Cyclic AMP; D008550:Melatonin; D009638:Norepinephrine