Ludovic Galas

Neuropeptide Y Inhibits the Biosynthesis of Sulfated Neurosteroids in the Hypothalamus through Activation of Y1 Receptors

We have recently shown that hydroxysteroid sulfotransferase (HST), the enzyme responsible for the biosynthesis of pregnenolone sulfate (Δ5PS) and dehydroepiandrosterone sulfate (DHEAS), is expressed in neurons located in the anterior preoptic area and the dorsal magnocellular nucleus of the frog diencephalon. As these two nuclei are richly innervated by NPY-immunoreactive fibers, we investigated the possible implication of NPY in the control of Δ5PS and DHEAS biosynthesis. Double labeling of frog brain sections revealed that 42% of the HST-immunoreactive perikarya in the diencephalon were contacted by NPY-containing fibers. In situ hybridization studies showed that Y1 and Y5 receptor mRNAs are expressed in the anterior preoptic area and the dorsal magnocellular nucleus. Pulse-chase experiments with 35S-labeled 3′-phosphoadenosine 5′-phosphosulfate as a sulfate donor demonstrated that frog NPY (fNPY) inhibited the conversion of [3H]Δ5P and [3H]dehydroepiandrosterone ([3H]DHEA) into [3H,35S]Δ5PS and [3H,35S...

Neuropeptide Y Inhibits Spontaneous α-Melanocyte-Stimulating Hormone (α-MSH) Release via a Y5 Receptor and Suppresses Thyrotropin-Releasing Hormone-Induced α-MSH Secretion via a Y1 Receptor in Frog Melanotrope Cells

In amphibians, the secretion of α-MSH by melanotrope cells is stimulated by TRH and inhibited by NPY. We have previously shown that NPY abrogates the stimulatory effect of TRH on α-MSH secretion. The aim of the present study was to characterize the receptor subtypes mediating the action of NPY and to investigate the intracellular mechanisms involved in the inhibitory effect of NPY on basal and TRH-induced α-MSH secretion. Y1 and Y5 receptor mRNAs were detected by RT-PCR and visualized by in situ hybridization histochemistry in the intermediate lobe of the pituitary. Various NPY analogs inhibited in a dose-dependent manner the spontaneous secretion of α-MSH from perifused frog neurointermediate lobes with the following order of potency porcine peptide YY (pPYY) > frog NPY (fNPY) > porcine NPY (pNPY)-2–36) > pNPY-(13–36) > [d-Trp32]pNPY > [Leu31,Pro34]pNPY. The stimulatory effect of TRH (10−86 m) on α-MSH release was inhibited by fNPY, pPYY, and [Leu31,Pro34]pNPY, but not by pNPY-(13–36) and [d-Trp32]pNPY. ...