Neuropeptide W is expressed in the noradrenalin-containing cells in the rat adrenal medulla

Distribution and Function of Neuropeptides W/B Signaling System

Neuropeptide W (NPW) and neuropeptide B (NPB) are two structurally and functionally related regulatory peptides, which are highly expressed in several brain regions and, additionally, in some peripheral tissues. Nevertheless, their distributions in the tissues are not similar. They act on target tissues via two subtypes of G protein-coupled receptors which are designated as NPBWR1 (GPR7) and NPBWR2 (GPR8), respectively, and possess different binding affinities. NPB activates NPBWR1, whereas NPW stimulates both the receptors with similar potency. Both of these peptides takes a part in the central regulation of neuroendocrine axes, feeding behavior, energy homeostasis, cardiovascular functions, circadian rhythm, pain sensation, modulation of inflammatory pain, and emotions. Over the past few years, studies have shown that NPB is also involved in sleep regulation. On the contrary, NPW participates in regulation of vascular myogenic tone, inhibits gastric tension sensitive vagal afferents and insulin secretion. Also, expression of NPW in the stomach is regulated by feeding. Abovementioned findings clearly demonstrate the functional diversity among NPW versus NPB signaling systems. In this review, signal transduction pathways of NPW/NPB are critically evaluated and observed together with mapping of expression of their signaling systems.

The role of neuropeptide W in energy homeostasis

Neuropeptide W is the endogenous ligand for G-protein-coupled receptors GPR7 and GPR8. In this review, we summarize findings on the distribution of neuropeptide W and its receptors in the central nervous system and the periphery, and discuss the role of NPW in food intake and energy homeostasis.

Neuropeptide W-Induced Hypophagia is Mediated Through Corticotropin-Releasing Hormone-Containing Neurons

Neuropeptide W (NPW), which was originally isolated from the porcine hypothalamus, has been identified as the endogenous ligand for both the NPBWR1 (GPR7) and NPBWR2 (GPR8) receptors. These receptors, which belong to the orphan G protein-coupled receptor (GPCR) family, share a high sequence homology with the opioid and somatostatin receptor families. NPW and NPBWR1 are widely distributed in the rat central nervous system (CNS). While the intracerebroventricular (i.c.v.) injection of NPW elevates plasma corticosterone levels, the intravenous administration of NPW in conjunction with a corticotropin-releasing hormone (CRH) antagonist blocks NPW-induced corticosterone secretion. It has been reported that NPW is involved in regulating the hypothalamus-pituitary-adrenal cortex (HPA) axis and that i.c.v. administration of NPW decreases feeding behavior. The aim of the present study was to ascertain if NPW's role in feeding regulation is mediated (or not) through corticotropin-releasing hormone (CRH)-containing neurons. We found that NPW-containing axon terminals make synapses with CRH-immunoreactive cell bodies and dendritic processes in the hypothalamic paraventricular nucleus (PVN). The central infusion of NPW significantly induced c-Fos expression in CRH-immunoreactive neurons in the mouse PVN, but not in vasopressin- or oxytocin-immunoreactive neurons. To determine if NPW regulates feeding behavior through CRH neurons, the feeding behavior of mice was studied following the i.c.v. administration NPW in the presence or absence of pretreatment with a CRH antagonist. While NPW administration decreased feeding activity, the CRH antagonist inhibited this effect. These results strongly suggest that NPW regulates feeding behavior through CRH neurons in the mouse brain.

Neuropeptide W stimulates adrenocorticotrophic hormone release via corticotrophin-releasing factor but not via arginine vasopressin

Neuropeptide W (NPW) was isolated as an endogenous ligand for NPBWR1, an orphan G protein-coupled receptor localized in the rat brain, including the paraventricular nucleus. It has been reported that central administration of NPW stimulates corticosterone secretion in rats. We hypothesized that NPW activates the hypothalamic-pituitary-adrenal (HPA) axis via corticotrophin-releasing factor (CRF) and/or arginine vasopressin (AVP). NPW at 1 pM to 10 nM did not affect basal or ACTH-induced corticosterone release from dispersed rat adrenocortical cells, or basal and CRF-induced ACTH release from dispersed rat anterior pituitary cells. In conscious and unrestrained male rats, intravenous administration of 2.5 and 25 nmol NPW did not affect plasma ACTH levels. However, intracerebroventricular (icv) administration of 2.5 and 5.0 nmol NPW increased plasma ACTH levels in a dose-dependent manner at 15 min after stimulation (5.0 vs. 2.5 nmol NPW vs. vehicle: 1802 ± 349 vs. 1170 ± 204 vs. 151 ± 28 pg/mL, respectively, mean ± SEM). Pretreatment with astressin, a CRF receptor antagonist, inhibited the increase in plasma ACTH levels induced by icv administration of 2.5 nmol NPW at 15 min (453 ± 176 vs. 1532 ± 343 pg/mL, p<0.05) and at 30 min (564 ± 147 vs. 1214 ± 139 pg/mL, p<0.05) versus pretreatment with vehicle alone. However, pretreatment with [1-(β-mercapto-β, β-cyclopentamethylenepropionic acid), 2-(Ο-methyl)tyrosine]-arg-vasopressin, a V1a/V1b receptor antagonist, did not affect icv NPW-induced ACTH release at any time (p>0.05). In conclusion, we suggest that central NPW activates the HPA axis by activating hypothalamic CRF but not AVP.

Neuropeptide w

Neuropeptide W (NPW), which was first isolated from the porcine hypothalamus, exists in two forms, consisting of 23 (NPW23) or 30 (NPW30) amino acids. These neuropeptides bind to one of two NPW receptors, either NPBWR1 (otherwise known as GPR7) or NPBWR2 (GPR8), which belong to the G protein-coupled receptor family. GPR7 is expressed in the brain and peripheral organs of both humans and rodents, whereas GPR8 is not found in rodents. GPR7 mRNA in rodents is widely expressed in several hypothalamic regions, including the paraventricular, supraoptic, ventromedial, dorsomedial, suprachiasmatic, and arcuate nuclei. These observations suggest that GPR7 plays a crucial role in the modulation of neuroendocrine function. The intracerebroventricular infusion of NPW has been shown to suppress food intake and body weight and to increase both heat production and body temperature, suggesting that NPW functions as an endogenous catabolic signaling molecule. Here we summarize our current understanding of the distribution and function of NPW in the brain.

Distribution of neuropeptide W in the rat brain

Neuropeptide W (NPW), which was recently isolated from the porcine hypothalamus, has been identified as the endogenous ligand of the orphan G protein-coupled receptors GPR7 (NPBWR1) and GPR8 (NPBWR2). Infusion of NPW increases food intake in the light phase, whereas in the dark phase, it has the opposite effect. In this study, we used RT-PCR analysis to examine the gene expression of NPW mRNA in the rat brain, and performed a detailed analysis of the distribution of NPW-positive neurons by use of immunohistochemistry at both the light and electron microscopic levels. NPW mRNA expression was demonstrated in the hypothalamic paraventricular nucleus (PVN), arcuate nucleus (ARC), ventromedial nucleus (VMH) and lateral hypothalamus (LH). At the light microscopic level, NPW-like immunoreactive (NPW-LI) cell bodies were found in the preoptic area (POA), PVN, ARC, VMH, LH, PMD (dorsal premammillary nucleus), periaqueductal gray (PAG), lateral parabrachial nucleus (LPB), and prepositus nucleus (Pr). NPW-LI axon terminals were shown in the POA, bed nucleus of the stria terminalis (BST), amygdala, PVN, ARC, VMH, LH, and PAG, LPB. In addition, at the electron microscopic level, NPW-LI cell bodies and dendritic processes were often seen to receive inputs from other unknown neurons in the ARC, PVN, VMH and amygdala. Our observations indicate that NPW-LI neurons widely distributed in the rat brain region. These finding suggest that NPW may have important roles in feeding behavior, energy homeostasis, emotional response and regulation of saliva secretion.