Injection of neuropeptide W into paraventricular nucleus of hypothalamus increases food intake

Neuropeptide W (NPW) is an endogenous ligand for G protein-coupled receptor 7 (GPR7). There are two forms of the peptide, designated as neuropeptide W-23 (NPW23) and neuropeptide W-30 (NPW30). In the current study we found that intracerebroventricular administration of NPW23 increased c-Fos immunoreactivity (IR) in a variety of brain sites, many of which are involved in the regulation of feeding. In particular, we noted that c-Fos IR levels were increased in hypocretin-expressing neurons in the perifornical region of the lateral hypothalamus (LH). We then studied whether injection of NPW23 into the paraventricular nucleus of the hypothalamus (PVN) and the LH increased food intake over a 24-h time period. Intra-PVN injection of NPW23 at doses ranging from 0.1 to 3 nmol increased feeding for up to 4 h, and doses ranging from 0.3 to 3 nmol increased feeding for up to 24 h. In contrast, only the 3-nmol dose of NPW23 increased feeding after administration into the LH. Together, these data suggest a modulatory role for NPW in the control of food intake.     

Developmental switch in neuropeptide Y and melanocortin effects in the paraventricular nucleus of the hypothalamus

Homeostatic regulation of energy balance in rodents changes dramatically during the first 3 postnatal weeks. Neuropeptide Y (NPY) and melanocortin neurons in the arcuate nucleus, a primary energy homeostatic center in adults, do not fully innervate the paraventricular nucleus (PVN) until the third postnatal week. We have identified two classes of PVN neurons responsive to these neuropeptides, tonically firing neurosecretory (NS) and burst-firing preautonomic (PA) cells. In neonates, NPY could inhibit GABAergic inputs to nearly all NS and PA neurons, while melanocortin regulation was minimal. However, there was a dramatic, age-dependent decrease in NPY responses specifically in the PA neurons, and a 3-fold increase in melanocortin responses in NS cells. These age-dependent changes were accompanied by changes in spontaneous GABAergic currents onto these neurons. This primarily NPYergic regulation in the neonates likely promotes the positive energy balance necessary for growth, while the developmental switch correlates with maturation of homeostatic regulation of energy balance.     

Intragranular co-storage of neuropeptide Y and arginine vasopressin in the paraventricular magnocellular neurons of the rat hypothalamus

Summary Certain populations of arginine vasopressin (AVP) neurons in the magnocellular paraventricular nucleus became immunoreactive for neuropeptide Y (NPY) when rats were treated with colchicine or monosodium glutamate (MSG). The co-storage of these peptides was examined by empooying a post-embedding electron-microscopic immunohistochemistry technique using goldlabeled antibodies to the two peptides. In colchicinetreated rats, the neuronal perikarya contained numerous secretory granules showing co-storage of the two peptides. The cells of the MSG-treated rats were characterized by having well-developed Golgi bodies with the granular structures also co-storing the two peptides, although the secretory granules in the perikarya were rather fewer than in the colchicine-treated rats. It is concluded that the destruction of the arcuate nucleus by MSG-treatment may potentiate the synthesis of NPY in AVP neurons, the synthesis of which is latent in intact animals.     

Role of alpha-1-adrenergic receptors in the regulation of corticotropin-releasing hormone mRNA in the paraventricular nucleus of the hypothalamus during stress

SUMMARY 1. The role of 1-adrenergic receptors on CRH mRNA levels in the PVN was studied in control and stressed rats receiving i.c.v. injections of the 1-adrenergic agonist, methoxamine, or the 1- antagonist, prazosin.2. Plasma ACTH increased significantly 60 min and 4 hr after a single injection of methoxamine (100 g, i.c.v.). No desensitization of this response was observed after repeated injections every 6 hr for 24 hr. Concomitantly, POMC mRNA in the anterior pituitary increased by 25% at 4 hr after a single injection and by 96% after repeated injections.3. CRH mRNA levels in the PVN increased by 131% after repeated injections for 24 hr, but were unchanged 4 hr after a single injection. Central 1-adrenergic blockade with prazosin did not prevent the increases in CRH mRNA following 4 hr of acute stress, but significantly reduced the increases observed 24 hr after an i.c.v. injection of 75 g of colchicine or after repeated i.p. hypertonic saline injections every 8 hr.4. These studies demonstrate that while 1-adrenergic receptors contribute to long-term increases of CRH mRNA levels in the PVN during prolonged stress, other factors are likely to be involved in the stimulation of CRH mRNA following acute stimulation.     

Electron-microscopic immunocytochemistry of neuropeptide Y immunoreactive innervation of vasopressin neurons in the paraventricular nucleus of the rat hypothalamus

The neuropeptide Y (NPY) immunoreactive synaptic input to neurons containing neurophysin II (NP II), the carrier protein of vasopressin (VP), was observed in the paraventricular nucleus (PVN) of the rat hypothalamus by double-labeling immunocytochemistry combining the preembedding peroxidase-antiperoxidase (PAP) method with the postembedding immunogold staining method at the electron-microscopic level. NPY-like immunoreactivities were detected by the PAP method in the dense granular vesicles (70-100 nm in diameter) in the immunoreactive presynaptic axon terminals. NP II-like immunoreactive large neurosecretory granules labeled with gold particles were found in the neurons receiving synaptic input of the NPY-like immunoreactive terminals. This suggests that NPY may be a neurotransmitter or neuromodulator and that NPY neurons may, through synaptic contacts, regulate the secretion of VP neurons.     

Steroid control of gonadotropin-releasing hormone secretion: associated changes in pro-opiomelanocortin and preproenkephalin messenger RNA expression in the ovine hypothalamus

The endogenous opioid peptides have been implicated in mediating the actions of estrogen and progesterone on GnRH release. We used in situ hybridization histochemistry to determine whether steroid-induced changes in GnRH/LH release in the female sheep are associated with changes in the cellular mRNA content of the precursors for beta-endorphin (pro-opiomelanocortin; POMC) and met-enkephalin (pre-proenkephalin; PENK). Two specific hypotheses were tested. First, that the inhibitory actions of progesterone are associated with an increase in opioid gene expression in specific hypothalamic nuclei. Our data support this hypothesis. Thus, an increase in progesterone was associated with increased POMC gene expression in the arcuate nucleus and PENK in the paraventricular nucleus. Further, the increase in POMC was restricted to regions of the arcuate nucleus that contain steroid sensitive beta-endorphin neurons. Our second hypothesis, that gene expression for the two opioid precursors would decrease prior to the start of the estradiol-stimulated GnRH surge, was not supported. Rather, POMC (but not PENK) gene expression in the arcuate nucleus was significantly higher in estradiol-treated animals than controls at the peak of the GnRH surge. These data suggest that beta-endorphin neurons in subdivisions of the arcuate nucleus and enkephalin neurons in the paraventricular nucleus are part of the neural network by which progesterone inhibits LH release. While enkephalin neurons may not play a role in estrogen positive feedback, increases in POMC mRNA in the arcuate nucleus at the time of the GnRH peak may be important for replenishing beta-endorphin stores and terminating estrous behavior.     

Relationship between neuropeptide Y and luteinizing-hormone-releasing hormone immunoreactivities in the hypothalamus and preoptic region

The purpose of this study was to examine the anatomical relationships of perikarya and fibers containing neuropeptide Y (NPY) and luteinizing-hormone-releasing hormone (LHRH) in the hypothalamus and preoptic region of female rats. In view of our previous report of stimulatory effects of estrogen on LHRH and NPY levels in the median eminence, animals were bilaterally ovariectomized and subsequently implanted subcutaneously with capsules containing estradiol benzoate in oil or vehicle. Following intracerebroventricular injection of colchicine, rats were perfused with fixative and their brains sectioned and processed for immunohistochemical visualization of NPY and LHRH in the same section and in consecutive sections. Estrogen treatment had no discernible effect on the distribution or relationship of these peptides. NPY-immunoreactive fibers were intimately associated with LHRH-labeled primary dendrites and perikarya in the medial preoptic region and horizontal limb of the diagonal band of Broca. Fibers containing NPY or LHRH overlapped extensively in the lateral palisade region of the median eminence and also in the subependymal and internal zones. The external zone of the median eminence displayed relatively less overlap of these peptide systems. LHRH-immunoreactive axons coursed among NPY-labeled perikarya in the arcuate nucleus and appeared to contact these cells. These results suggest that NPY-containing axons may influence LHRH-positive neurons at the cell body and also at the site of axon termination in the median eminence. LHRH-containing axons appear to contact NPY-immunoreactive perikarya in the arcuate nucleus and may interact with terminals in the median eminence. This arrangement may provide a mechanism for communication between NPY and LHRH neurons and for the neuroendocrine coordination of hypothalamic NPY and LHRH secretion before ovulation.     

Evidence that the anterior hypothalamus contributes to the control of tonic secretion of follicle-stimulating hormone in the female rat

A horizontal knife cut was placed between the dorsal anterior hypothalamic area (DAHA) and the medial basal hypothalamus to examine the role of the DAHA in the selective secretion of follicle-stimulating hormone (FSH) following unilateral ovariectomy (ULO) and bilateral ovariectomy of the rat. Complete cuts markedly attenuated the increase in FSH observed 8 h after ULO, whereas incomplete or sham cuts did not. Concentration of luteinizing hormone (LH) did not increase in any group. These cuts also blocked the prolongation of estrous FSH secretion observed in long-term hemicastrated rats, since FSH levels on estrus were significantly lower in rats with complete cuts than in those rats given sham or incomplete cuts. In contrast, neural surgery had no effect on proestrous FSH concentrations. Finally, when FSH levels were monitored 2 days after bilateral ovariectomy, the postcastration rise in FSH was not altered by any neurosurgical procedures. These results support the hypothesis that a neural system originating in, or passing through, the DAHA is necessary for the selective increase in FSH following ULO.     

烫伤对大鼠下丘脑室旁核内皮素—1合成和分泌的影响

目的研究烫伤后下丘脑室旁核(PVH)内皮素-1(ET-1)的合成和分泌改变,探讨PVHET-1在烫伤中的病理生理学意义。方法用原位杂交和免疫组织化学方法观察了烫伤后PVHET-1合成和分泌的变化,并用通用图象颗粒分析法检测单位面积内ET-1mRNA阳性杂交信号的强度和ET-1样免疫反应物(ET-1-ir)免疫反应强度。结果烫伤后15minPVH神经元胞浆内ET-1mRNA阳性杂交信号与对照组相比未见明显差异,烫伤后60min和180minPVH神经元胞浆内ET-1mRNA阳性杂交信号较对照组(100％±25％)明显增多,强度明显增高,分别为138％±26％(P<0．05)和167％±18％(P<0.01);而烫伤后15minPVH神经元胞浆内ET-1阳性反应物明显减少,免疫反应物强度为6．3％±1．5％,显著低于对照组(P<0．01),烫伤后60min和180min逐渐回升,分别为23．1％±2．9％和44．1％±3．8％,但仍显著低于对照组(P＜0．01)。结论烫伤后PVHET-1合成和分泌增加。     

Nuclear inclusions in paraventricular nucleus neurons of the rat hypothalamus

Summary This paper deals with the ultrastructure of two types of intranuclear inclusions, microfilamentous spindle-shaped and crystalloid, present in paraventricular nucleus neurons of adult normal rats. These inclusions appear occasionally in some non-secretory neurons of the parvocellular system, but have never been seen in neurosecretory cells of the magnocellular system. The microfilamentous spindle-shaped inclusions show a close spatial relationship with the granulofibrillar body and interchromatin granules.The distribution and functional significance of such structures are discussed in the light of recent ultrastructural and biochemical studies on nuclear inclusions.     

Subsurface cisterns in paraventricular nuclei of the hypothalamus of the rat

Summary Structures identified as subsurface cisterns (SSC's) were found in neurons of the paraventricular nuclei of the rat hypothalamus. They appeared as cytoplasmic organelles consisting most often of stacks of parallel cisterns apposed to the neuronal plasmalemma. These SSC's were located in the interneurons of the parvocellular system, but not in neurosecretory cells and glial cells. SSC's were seen at zones of cytoplasm apposed to neuronal or glial cell processes, showing in some instances specific relationships with synaptic areas.The morphological features of these SSC's are described, and their possible functional significance is briefly discussed.     

Localization of neuropeptide Y-like immunoreactivity in the cat hypothalamus

The distribution pattern of neuropeptide Y-like immunoreactivity (NPY-Li) in cat hypothalamus was studied using avidin-biotin modification of immunocytochemical method. This study showed cell bodies containing NPY-Li in the periventricular and the infundibular nuclei and also a moderate number of neurons with NPY-Li in the ventromedial nucleus, an observation not reported in earlier studies. Fibers with NPY-Li were noted throughout the hypothalamus, but most prominently within the periventricular regions. The location of NPY cells within the hypothalamus suggests the possibility of an interaction with dopaminergic and other proopiomelanocortinergic neurons.     

Tumor anorexia: effects on neuropeptide Y and monoamines in paraventricular nucleus

Paraventricular (PVN) concentrations of neuropeptide Y (NPY), serotonin (5-HT) and dopamine (DA) in anorectic tumor-bearing (TB) rats were measured before and after tumor resection. At onset of anorexia in TB versus non-tumor bearing (NTB) Controls 5-HT increased from 12.19+/-0.49 pg/microg to 14.89+/-0.81 pg/microg ( P<0.05 ) while DA and NPY decreased from 7.34+/-0.42 pg/microg to 4.97+/-0.56 pg/microg and 23.47+/-4.27 pg/microg to 13.64+/-1.44 pg/microg, respectively ( P<0.05 ). After tumor resection, these neuromediators normalized when compared to sham-operated NTB rats. NTB pair-fed Controls were also studied. We conclude that the increased 5-HT and the decreased DA and NPY concentrations in PVN are associated with cancer anorexia and that the NPY food stimulatory effect is linked to serotoninergic and dopaminergic systems in hypothalamus.     

Optimization of neuropeptide extraction from the mouse hypothalamus

Sample preparation for neuropeptidomic studies is a critical issue since protein degradation can produce high levels of peptides that obscure the endogenous neuropeptides. We compared different extraction conditions for the recovery of neuropeptides and the formation of protein breakdown fragments from mouse hypothalami. Sonication and heating in water (70 degrees C for 20 min) followed by cold acid and centrifugation enabled the efficient extraction of many neuropeptides without the formation of protein degradation fragments seen with hot acid extractions. The hot water/cold acid extraction procedure resulted in the reproducible recovery of many hypothalamic peptides, including several novel peptides.     

Ultrastructural characteristics of vasopressin-containing neurons in the paraventricular nucleus of the hypothalamus

Summary Vasopressin-containing neurons, identified by immunocytochemistry, are located predominantly in the posterior magnocellular division of the paraventricular nucleus of the rat hypothalamus. By electron microscopy, the immunoreaction product is seen within the cell bodies and neuronal processes. In the perikarya and dendritic processes, the immunoreactive material is associated primarily with neurosecretory granules. Axonal processes, identified by their content of microtubules and accumulation of neurosecretory granules, show the immunoreaction product in association with both of these organelles. Afferent axo-dendritic, axo-somatic and putative axo-axonic synapses with immunostained vasopressinergic neurons can be identified. The presynaptic profiles do not contain immunoreactive material. This study contributes to the ultrastructural characterization of vasopressinergic neurons in the paraventricular nucleus and of their afferent synaptic input.Supported by NIH Grants HD-12956 and 2SO7RR05403