Hypothalamic Neuropeptide Research Articles

The kiss2/kiss2r system directly modulates the activity of the pituitary gland in largemouth bass (Micropterus salmoides)

The kisspeptin system, which involves hypothalamic neuropeptides, plays pivotal roles in the regulation of teleost reproduction. A previous study suggested that the kiss2/kissr2 system in largemouth bass (Micropterus salmoides) was involved in regulating gonadal development through the hypothalamus-pituitary-gonad (HPG) axis. However, whether the kiss2/kiss2r system directly regulates the activity of pituitary gland were not studied. This study aimed to elucidate the detailed mechanism of kisspeptin-induced effects on gonadotropin hormone-producing cells in vivo and in vitro. In situ hybridization analysis revealed very widespread expression of kiss2r mRNA in the optic tectum, hypothalamus and pituitary. In the pituitary, kiss2r-expressing cells were mainly located in the proximal pars distalis and pars intermedia, among which the fshβ- and lhβ-positive cells exhibited expression of kiss2r messengers. Furthermore, primary culture of pituitary cells and peptide administration experiments revealed that the Kiss2-10 peptide stimulates the expression of fshβ and lhβ and the secretion of FSH and LH in 24 h. In addition, histology analysis revealed that three injections of the Kiss2-10 peptide promoted ovary development and increased oocyte size but had little effect on testis development. These results suggested that the intrapituitary kisspeptinergic system, as a hypophysiotropic neuropeptide factor, directly modulates of gonadotroph function. This study will help uncover the reproductive endocrinology network and improve artificial breeding technology for largemouth bass.

Molecular cloning and bioinformatic characterization of Gonadotropin Inhibitory Hormone (GnIH) and its receptors in the freshwater murrel, Channa punctatus (Bloch, 1793).

Gonadotropin inhibitory hormone belonging to the RFamide peptide family, a hypothalamic neuropeptide, regulates Hypothalamus-pituitary-gonadal (HPG) axis and inhibits gonadal development. GnIH polypeptide precursor has an Arg-Phe-NH2 (RFamide) motif at the C-terminal, which has LPXRF (X = Q or L) domain. The actions of GnIH are mediated through G-protein coupled receptors and upto threereceptors have been characterized in many teleosts. GnIH exerts its inhibitory effect on the HPG axis through direct interaction with GnRH and Kisspeptin neurons in the brain and acts directly on the pituitary gonadotrophs. To decipher the role of GnIH in Indian freshwater murrel, Channa punctatus, we sequenced the cDNA encoding GnIH and its two receptors. The identified GnIH mRNA encodes three RFamide peptides having -MPMRF, -MPQRF, and -LPQRFamide motifs. In silico analysis of the amino acid sequence of GnIH exhibits its molecular and functional properties and the protein-protein interaction with significant factors regulating the HPG axis. The 3-D structure of GnIH and its receptors, provides more relevant information about the active residues of these proteins which might be involved in their functioning and interaction with other proteins. Molecular dynamic simulation of GnIH protein has provided more insight into its dynamic behavior. The expression of GnIH and its receptors, shows an inverse correlation with gonadal development during the annual reproductive cycle.

Sex differences in pituitary corticotroph excitability.

Stress-related illness represents a major burden on health and society. Sex differences in stress-related disorders are well documented, with women having twice the lifetime rate of depression compared to men and most anxiety disorders. Anterior pituitary corticotrophs are central components of the hypothalamic-pituitary-adrenal (HPA) axis, receiving input from hypothalamic neuropeptides corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP), while regulating glucocorticoid output from the adrenal cortex. The dynamic control of electrical excitability by CRH/AVP and glucocorticoids is critical for corticotroph function; however, whether corticotrophs contribute to sexually differential responses of the HPA axis, which might underlie differences in stress-related disorders, is very poorly understood. Using perforated patch clamp electrophysiology in corticotrophs from mice expressing green fluorescent protein under the control of the Pomc promoter, we characterized basal and secretagogue-evoked excitability. Both male and female corticotrophs show predominantly single-spike action potentials under basal conditions; however, males predominantly display spikes with small-amplitude (<20mV) afterhyperpolarizations (B-type), whereas females displayed a mixture of B-type spikes and spikes with a large-amplitude (>25mV) afterhyperpolarization (A-type). In response to CRH, or CRH/AVP, male cells almost exclusively transition to a predominantly pseudo-plateau bursting, whereas only female B-type cells display bursting in response to CRH±AVP. Treatment of male or female corticotrophs with 1nM estradiol (E2) for 24-72h has no effect on the proportion of cells with A- or B-type spikes in either sex. However, E2 results in the cessation of CRH-induced bursting in both male and female corticotrophs, which can be partially reversed by adding a BK current using a dynamic clamp. RNA-seq analysis of purified corticotrophs reveals extensive differential gene expression at the transcriptional level, including more than 71 mRNAs encoding ion channel subunits. Interestingly, there is a two-fold lower level (p < 0.01) of BK channel pore-forming subunit (Kcnma1) expression in females compared to males, which may partially explain the decrease in CRH-induced bursting. This study identified sex differences at the level of the anterior pituitary corticotroph ion channel landscape and control of both spontaneous and CRH-evoked excitability. Determining the mechanisms of sex differences of corticotroph and HPA activity at the cellular level could be an important step for better understanding, diagnosing, and treating stress-related disorders.

Gonadotropin inhibitory-hormone modulates neurosteroids-synthesizing enzymes expression and aggressive behavior in male sea bass, Dicentrarchus labrax

Neurosteroids are involved in the regulation of multiple behavioral and physiological processes and metabolic activities in the vertebrate brain. However, central mechanisms of how neurosteroid synthesis is regulated is far to be understood. Gonadotropin-inhibitory hormone (GNIH) is a hypothalamic neuropeptide that negatively regulates gonadotropin secretion but also inhibits sexual and aggressive behaviors in birds and mammals by modulating aromatase enzyme and neuroestrogen synthesis. In a previous study performed in male sea bass, we reported that Gnih inhibited the reproductive axis by acting at the three levels of the brain-pituitary-gonad axis. Moreover, the presence of Gnih cells and fibers in the telencephalon, mesencephalon and rhombencephalon suggests a role of Gnih in regulating other important brain functions in sea bass, including behavior. In this study, we have analyzed the effects of the intracerebroventricular (icv) injection of sbGnih-2 on the brain and pituitary expression of the main neurosteroids-synthesizing enzymes (stAR, cyp17, 3β-hsd, 17β-hsd, cyp19b, cyp7b), as well as on estrogen and androgen receptors (erα, erβ1, erβ2, ar). A combination of immunohistochemistry and in situ hybridization was also used to identify putative interaction of Gnih- and aromatase-positive cells. We also performed a mirror test study as a proxy to measure aggression levels and agonistic behavior after icv injection of sbGnih-2. Central administration of sbGnih-2 at different doses reduced the transcript levels of 3β-hsd and 17β-hsd, and increased the expression of cyp19b (brain aromatase) in the sea bass brain. Neuroanatomical results suggest that paracrine and neuroendocrine actions could mediate Gnih effects on aromatase expression. Central administration of sbGnih-2 also decreased the pituitary expression of 17β-hsd and estrogen receptors (erβ2). The mirror test analysis showed that sbGnih-2 affected the agonistic/aggressive behavior of sea bass as revealed by the decreased interaction with the mirror, lower time spent in the mirror zone, increased latency to establish contact with the mirror and higher mean distance to the mirror zone. In contrast, locomotor activity parameters measured were not affected by sbGnih-2 injection. Taken together, our results showed for the first time in fish that Gnih inhibits social-aggressive behavior and affects the gene expression of neurosteroid-synthesizing enzymes giving rise to neuroandrogens and neuroestrogens in the sea bass brain.

The Role of Hypothalamic Neuropeptides in Regulation of Liver Functions in Health and Disease

The communication between brain and peripheral tissues is mediated by neuropeptides that coordinate the functions of each organ with the activities of the entire body in specific environmental conditions. Hypothalamic neuropeptides act as neurotransmitters and hormones to regulate the physiology of food intake, digestion, and metabolism, having a direct or indirect impact on the liver. Investigations on liver pathologies found that dysfunctions of neuropeptides and their receptors are associated with liver disorders such as non-alcoholic fatty liver disease, steatohepatitis, cholestasis, cirrhosis, and liver cancer. In this article, we reviewed neuropeptides that regulate energy homeostasis and lipid and glucose metabolism in the liver and are associated with liver injuries. Firstly, peptides involved in regulatory processes in the brain and liver, such as neuropeptide Y, agouti-related protein, and the galanin family, are related to obesity and its comorbidities, including type 2 diabetes and metabolic syndrome, are presented. Secondly, a comprehensive review of neuropeptides such as secretin, vasoactive intestinal peptide, substance P, and somatostatin, which are involved in liver injuries unrelated to obesity; i.e., cholestasis-induced biliary hyperplasia, cirrhosis, hepatocellular carcinoma, and cholangiocarcinoma, is also presented. The cellular and molecular mechanisms underlining liver injuries related to the dysfunction of these neuropeptides and receptors are also described.

Peripheral and Central Impact of Methionine Source and Level on Growth Performance, Circulating Methionine Levels and Metabolism in Broiler Chickens.

The present study was designed to evaluate the effects of DL-methionine (DL-Met) 2-hydroxy-4-(methylthio) butanoic acid (HMTBa), or S-(5'-Adenosyl)-L-methionine chloride (SAM), using feeding trial and central administration, on live performance, plasma metabolites, and the expression of feeding-related hypothalamic neuropeptides in broilers raised to a market age (35 d). Final average body weight (BW) and feed conversion ratio (FCR) from the feeding trial exceeded the performance measurements published by the primary breeder. At d35, the MTBHa group had better BW and lower feed intake, which resulted in a better FCR than the DL-Met group at 87 TSAA to lysine. At the molecular levels, the expression of hypothalamic neuropeptide (NPY) and monocarboxylate transporter (MCT) 2 did not differ between all treated groups; however, the mRNA abundances of hypothalamic MCT1 and orexin (ORX) were significantly upregulated in DL-Met- treated groups compared to the control. The ICV administration of SAM significantly reduced feed intake at all tested periods (from 30 to 180 min post injection) compared to the aCSF-treated group (control). The central administration of HMTBa increased feed intake, which reached a significant level only 60 min post administration, compared to the control group. ICV administration of DL-Met slightly increased feed intake compared to the control group, but the difference was not statistically discernable. Quantitative real-time PCR analysis showed that the hypothalamic expression of NPY, cocaine- and amphetamine-regulated transcript, MCT1, and MCT2 was significantly upregulated in the ICV-HMTBa group compared to the aCSF birds. The hypothalamic expression of the mechanistic target of rapamycin (mTOR), AMP-activated protein kinase (AMPKα1), D-amino acid oxidase, and hydroxyacid oxidase was significantly upregulated in DL-Met compared to the control group. The mRNA abundances of ORX were significantly increased in the hypothalamus of both DL-Met and HMTBa groups compared to the aCSF birds; however, mTOR gene expression was significantly downregulated in the SAM compared to the control group. Taken together, these data show, for the first time, that DL-Met and HMTBa have a common downstream (ORX) pathway, but also a differential central pathway, typically NPY-MCT for HMTBa and mTOR-AMPK for methionine.

Orexin receptors in paraventricular nucleus influence sexual behavior via regulating the sympathetic outflow in males.

Orexins are hypothalamic neuropeptides associated with various neurophysiological activities such as sleep, arousal, and reward. However, there are few studies investigating the relationships between orexin receptors in the paraventricular nucleus and sexual behaviors. To explore the roles of orexin receptors in the paraventricular nucleus on sexual behaviors and uncover its potential mechanisms in males. Orexin A, orexin 1 receptor antagonist SB334867, and orexin 2 receptor antagonist TCS-OX2-29 were microinjected into the paraventricular nucleus to investigate the effects of orexin receptors on copulatory behavior testing of C57BL/6 mice. To explore if ejaculation could activate orexin 1 receptor-expressing neurons in the paraventricular nucleus, fluorescence immunohistochemical double staining was utilized. The levels of serum norepinephrine were measured and the lumbar sympathetic nerve activity was recorded to reflect the sympathetic nervous system activity. Moreover, the bulbospongiosus muscle-electromyogram was recorded and analyzed. To test whether perifornical/lateral hypothalamic area orexinergic neurons directly projected to the paraventricular nucleus, virus retrograde tracing technology was utilized. Orexin A significantly enhanced sexual performance by shortening the intromission and ejaculation latencies, and increasing the mount and intromission frequencies, while the opposite outcomes appeared with SB334867. However, TCS-OX2-29 had no significant effects on sexual behaviors. Moreover, orexin A increased lumbar sympathetic nerve activity and the levels of serum norepinephrine, while SB334867 decreased lumbar sympathetic nerve activity and norepinephrine, which caused a significant decrease in sympathetic nervous system outflow. Meanwhile, a robust increase in the bulbospongiosus muscle-electromyogram activity was identified after microinjecting orexin A. Furthermore, cFos immunopositive cells were increased and double stained with orexin 1 receptor-expressing neurons in the mating group. Additionally, the retrograde tracing results demonstrated that orexinergic neurons in the perifornical/lateral hypothalamic area directly projected to the paraventricular nucleus. Orexin 1 receptor in the paraventricular nucleus could influence the ejaculatory reflex via mediating the sympathetic nervous system activity, which might be of great importance in the treatment of premature ejaculation in the future.

Epigenetic silencing of selected hypothalamic neuropeptides in narcolepsy with cataplexy

Narcolepsy with cataplexy isa sleep disorder caused by deficiency in the hypothalamic neuropeptide hypocretin/orexin (HCRT), unanimously believed to result from autoimmune destruction of hypocretin-producing neurons. HCRT deficiency can also occur in secondary forms of narcolepsy and be only temporary, suggesting it can occur without irreversible neuronal loss. The recent discovery that narcolepsy patients also show loss of hypothalamic (corticotropin-releasing hormone) CRH-producing neurons suggests that other mechanisms than cell-specific autoimmune attack, are involved. Here, we identify the HCRT cell-colocalized neuropeptide QRFP as the best marker of HCRT neurons. We show that if HCRT neurons are ablated in mice, in addition toHcrt, Qrfp transcript is also lost in the lateral hypothalamus, while in mice where only theHcrtgene is inactivated Qrfp is unchanged. Similarly, postmortem hypothalamic tissues of narcolepsy patients show preservedQRFPexpression, suggesting the neurons are present but fail to actively produce HCRT. We show that the promoter of theHCRTgene of patients exhibits hypermethylation at a methylation-sensitive and evolutionary-conserved PAX5:ETS1 transcription factor-binding site, suggesting the gene issubject to transcriptional silencing. We show also that in addition to HCRT,CRHand Dynorphin (PDYN) gene promoters, exhibit hypermethylation in the hypothalamus of patients. Altogether, we propose that HCRT,PDYN, andCRH are epigenetically silenced by a hypothalamic assault (inflammation) in narcolepsy patients,without concurrent cell death. Since methylation is reversible, our findings open the prospect of reversing or curing narcolepsy.

Palmitate alters miR-2137 and miR-503-5p to induce orexigenic Npy in hypothalamic neuronal cell models: Rescue by oleate and docosahexaenoic acid.

MicroRNAs (miRNAs) are short noncoding RNA implicated in the pathogenesis of obesity. One cause of obesity is excess exposure to the saturated fatty acid palmitate that can alter miRNA levels in the periphery. Palmitate also promotes obesity by acting on the hypothalamus, the central coordinator of energy homeostasis, to dysregulate hypothalamic feeding neuropeptides and induce ER stress and inflammatory signaling. We hypothesized that palmitate would alter hypothalamic miRNAs that control genes involved in energy homeostasis thereby contributing to the obesity-promoting effects of palmitate. We found that palmitate upregulated 20 miRNAs and downregulated six miRNAs in the orexigenic NPY/AgRP-expressing mHypoE-46 cell line. We focused on delineating the roles of miR-2137 and miR-503-5p, as they were strongly up- and downregulated by palmitate, respectively. Overexpression of miR-2137 increased Npy mRNA levels and downregulated Esr1 levels, while increasing C/ebpβ and Atf3 mRNA. Inhibiting miR-2137 had the opposite effect, except on Npy, which was unchanged. The most downregulated miRNA by palmitate, miR-503-5p, negatively regulated Npy mRNA levels. Exposure to the unsaturated fatty acids oleate or docosahexaenoic acid completely or partially blocked the effects of palmitate on miR-2137 and miR-503-5p as well as Npy, Agrp, Esr1, C/ebpβ and Atf3. MicroRNAs may therefore contribute to palmitate actions in dysregulating NPY/AgRP neurons. Effectively combating the deleterious effects of palmitate is crucial to help prevent or reduce the impact of obesity.

Immunohistochemistry of Leukemia Inhibitory Factor and Integrin αVβ3 in Mouse Endometrium Following Kisspeptin-54 Ovulation Trigger.

Kisspeptin (KP) is a group of hypothalamic neuropeptides encoded by KISS-1 gene. KP-54, a 54-amino-acid peptide, helps regulate the hypothalamic-pituitary-ovarian axis and plays a potential role in implantation. C57BL/6J female mice were superovulated via intraperitoneal injection of 5 International Units (IU) pregnant mare serum gonadotrophin (day 1). Forty-eight hours later, mice (5/group) were injected with phosphate-buffered saline (PBS) (group A), 5IU human chorionic gonadotrophin (hCG) (group B), or 3nmol KP-54 (group C). On day 7, mice were euthanized and uteri excised to create paraformaldehyde-fixed paraffin-embedded sections that were immunostained for the implantation markers: leukemia inhibitory factor (LIF) and integrin αVβ3 (ITG αVβ3). Slides were scored for intensity of staining in endometrial glandular epithelium (GE) and stromal cells (SCs) via histoscore (H-score). Data were analyzed using the Kruskal-Wallis test followed by the Mann-Whitney U test for pairwise comparisons. LIF expression was significantly higher in GE and SCs of mice triggered with KP-54 compared to placebo (P = .009 for both), but only higher than hCG trigger group in SCs (P = .009). Meanwhile, ITG αVβ3 expression was significantly higher in SCs of mice triggered with KP-54 compared to placebo (P = .028). In conclusion, using KP-54 as an ovulation trigger resulted in higher expression of the implantation markers LIF and ITG αVβ3 in mice endometrium compared to hCG or placebo. This suggests a potential role for KP-54 trigger in improving embryo implantation in clinical IVF. However, further studies are needed to correlate these results with clinical implantation rates and pregnancy outcomes.

Malocclusion impairs cognitive behavior via AgRP signaling in adolescent mice.

Occlusal disharmony induced by deteriorating oral health conditions, such as tooth loss and decreased masticatory muscle due to sarcopenia, is one of the causes of cognitive impairment. Chewing is an essential oral function for maintaining cognitive function not only in the elderly but also in young people. Malocclusion is an occlusal disharmony that commonly occurs in children. The connection between a decline in cognitive function and malocclusion in children has been shown with chronic mouth breathing, obstructive sleep apnea syndrome, and thumb/digit sucking habits. However, the mechanism of malocclusion-induced cognitive decline is not fully understood. We recently reported an association between feeding-related neuropeptides and cognitive decline in adolescent mice with activity-based anorexia. The aim of the present study was to assess the effects of malocclusion on cognitive behavior and clarify the connection between cognitive decline and hypothalamic feeding-related neuropeptides in adolescent mice with malocclusion. Four-week-old mice were randomly assigned to the sham-operated solid diet-fed (Sham/solid), sham-operated powder diet-fed (Sham/powder), or malocclusion-operated powder diet-fed (Malocclusion/powder) group. We applied composite resin to the mandibular anterior teeth to simulate malocclusion. We evaluated cognitive behavior using a novel object recognition (NOR) test, measured hypothalamic feeding-related neuropeptide mRNA expression levels, and enumerated c-Fos-positive cells in the hypothalamus 1 month after surgery. We also evaluated the effects of central antibody administration on cognitive behavior impairment in the NOR test. The NOR indices were lower and the agouti-related peptide (AgRP) mRNA levels and number of c-Fos-positive cells were higher in the malocclusion/powder group than in the other groups. The c-Fos-positive cells were also AgRP-positive. We observed that the central administration of anti-AgRP antibody significantly increased the NOR indices. The present study suggests that elevated cerebral AgRP signaling contributes to malocclusion-induced cognitive decline in adolescents, and the suppression of AgRP signaling can be a new therapeutic target against cognitive decline in occlusal disharmony.

Effect of dietary bile acids supplementation on growth performance, feed utilization, intestinal digestive enzyme activity and fatty acid transporters gene expression in juvenile leopard coral grouper (Plectropomus leopardus)

This study aimed to evaluate the effects of dietary bile acids on growth performance, feed utilization, body composition, digestive enzyme activity, and related gene expression in juvenile leopard coral grouper (Plectropomus leopardus). Five diets with varying levels of dietary bile acids (0, 0.15, 0.3, 0.45 and 0.6%) were formulated and each diet was fed to triplicate groups of 15 fish (13.14 ± 0.14 g) for ten weeks. Results showed that the significant enhancement in weight gain (WG) and specific growth rate (SGR) was observed in fish fed 0.3% bile acids (P &amp;lt; 0.05). Additionally, feed conversion ratio (FCR) was significantly improved with bile acids inclusion (P &amp;lt; 0.05). Higher feed intake was also recorded in bile acids inclusion groups, and significantly up-regulated gene expression of hypothalamus neuropeptide Y (NPY) was found in 0.3% group compared with the control group (P &amp;lt; 0.05). Dietary bile acids (0.3%) significantly decreased lipid deposition in the whole-body (P &amp;lt; 0.05), and lower hepatosomatic index (HSI) and viscerosomatic index (VSI) were also found in this group. Moreover, intestinal trypsin and lipase activities were significantly increased in 0.3% group (P &amp;lt; 0.05) to promote feed digestion. In addition, the relative expression levels of intestinal fatty acid binding protein 2 (FABP2) significantly up-regulated with inclusion of dietary bile acids, suggesting an enhancement of fatty acid transport (P &amp;lt; 0.05). In contrast, cholesterol transport related genes NPC1 like intracellular cholesterol transporter 1 (NPC1L1) and CD36 were notably down-regulated as bile acids inclusion (P &amp;lt; 0.05). This study provides valuable information for the formulation of diets for juvenile coral trout and indicates that dietary bile acids could potentially be used to improve growth performance and feed utilization.

Targeting orexin receptors: Recent advances in the development of subtype selective or dual ligands for the treatment of neuropsychiatric disorders.

Orexin-A and orexin-B, also named hypocretin-1 and hypocretin-2, are two hypothalamic neuropeptides highly conserved across mammalian species. Their effects are mediated by two distinct G protein-coupled receptors, namely orexin receptor type 1 (OX1-R) and type 2 (OX2-R), which share 64% amino acid identity. Given the wide expression of OX-Rs in different central nervous system and peripheral areas and the severalpathophysiological functions in which they are involved, including sleep-wake cycle regulation (mainly mediated by OX2-R), emotion, panic-like behaviors, anxiety/stress, food intake, and energy homeostasis (mainly mediated by OX1-R), both subtypes represent targets of interest for many structure-activity relationship (SAR) campaigns carried out by pharmaceutical companies and academies. However, before 2017 the research was predominantly directed towards dual-orexin ligands, and limited chemotypes were investigated. Analytical characterizations, including resolved structures for both OX1-R and OX2-R in complex with agonists and antagonists, have improved the understanding of the molecular basis of receptor recognition and are assets for medicinal chemists in the design of subtype-selective ligands. This review is focused on the medicinal chemistry aspects of small molecules acting as dual or subtype selective OX1-R/OX2-R agonists and antagonists belonging to different chemotypes and developed in the last years, including radiolabeled OX-R ligands for molecular imaging. Moreover, the pharmacological effects of the most studied ligands in different neuropsychiatric diseases, such as sleep, mood, substance use, and eating disorders, as well as pain, have been discussed. Poly-pharmacology applications and multitarget ligands have also been considered.

Changes in sensorimotor cortex oscillatory activity by orexin-A in the ventrolateral preoptic area of the hypothalamus reflect increased muscle tone.

Orexin-A (OXA) is a hypothalamic neuropeptide implicated in the regulation of wakefulness, appetite, reward processing, muscle tone, motor activity, and other physiological processes. The broad range of systems affected stems from the widespread projections of orexin neurons toward multiple brain regions regulating numerous physiological processes. Orexin neurons integrate nutritional, energetic, and behavioral cues and modulate the functions of target structures. Orexin promotes spontaneous physical activity (SPA), and we recently showed that orexin injected into the ventrolateral preoptic area (VLPO) of the hypothalamus increases behavioral arousal and SPA in rats. However, the specific mechanisms underlying the role of orexin in physical activity are unknown. Here we tested the hypothesis that OXA injected into the VLPO alters the oscillatory activity in the electroencephalogram (EEG) to reflect an increased excitability of the sensorimotor cortex, which may explain the associated increase in SPA. The results showed that OXA increased wakefulness following injections into the VLPO. In addition, OXA altered the power spectrum of the EEG during the awake state by decreasing the power of 5-19 Hz oscillations and increasing the power of >35 Hz oscillations, which are markers of increased sensorimotor excitability. Consistently, we found that OXA induced greater muscle activity. Furthermore, we found a similar change in power spectrum during slow-wave sleep, which suggests that OXA altered the EEG activity in a fundamental way, even in the absence of physical activity. These results support the idea that OXA increases the excitability of the sensorimotor system, which may explain the corresponding increase in awake time, muscle tone, and SPA.

Oxytocin attenuates microglial activation and restores social and non-social memory in APP/PS1 Alzheimer model mice

Alzheimer's disease (AD) is characterized by neurodegeneration, memory loss, and social withdrawal. Brain inflammation has emerged as a key pathogenic mechanism in AD. We hypothesized that oxytocin, a pro-social hypothalamic neuropeptide with anti-inflammatory properties, could have therapeutic actions in AD. Here, we investigated oxytocin expression in experimental models of AD, and evaluated the therapeutic potential of treatment with oxytocin. Amyloid-β peptide oligomers (AβOs) reduced oxytocin expression invitro and invivo, and treatment with oxytocin prevented microglial activation induced by AβOs in purified microglial cultures. Treatment of aged APP/PS1 mice, a mouse model of AD, with intranasal oxytocin attenuated microglial activation and favored deposition of Aβ in dense core plaques, a potentially neuroprotective mechanism. Remarkably, treatment withoxytocin alleviated social and non-social memory impairments in agedAPP/PS1 mice. Our findings point to oxytocin as a potential therapeutic target to reduce brain inflammation and correct memory deficits inAD.

Peripheral vs. core body temperature as hypocretin/orexin neurons degenerate: Exercise mitigates increased heat loss

Hypocretins/Orexins (Hcrt/Ox) are hypothalamic neuropeptides implicated in diverse functions, including body temperature regulation through modulation of sympathetic vasoconstrictor tone. In the current study, we measured subcutaneous (Tsc) and core (Tb) body temperature as well as activity in a conditional transgenic mouse strain that allows the inducible ablation of Hcrt/Ox-containing neurons by removal of doxycycline (DOX) from their diet (orexin-DTA mice). Measurements were made during a baseline, when mice were being maintained on food containing DOX, and over 42 days while the mice were fed normal chow which resulted in Hcrt/Ox neuron degeneration. The home cages of the orexin-DTA mice were equipped with running wheels that were either locked or unlocked. In the presence of a locked running wheel, Tsc progressively decreased on days 28 and 42 in the DOX(-) condition, primarily during the dark phase (the major active period for rodents). This nocturnal reduction in Tsc was mitigated when mice had access to unlocked running wheels. In contrast to Tsc, Tb was largely maintained until day 42 in the DOX(-) condition even when the running wheel was locked. Acute changes in both Tsc and Tb were observed preceding, during, and following cataplexy. Our results suggest that ablation of Hcrt/Ox-containing neurons results in elevated heat loss, likely through reduced sympathetic vasoconstrictor tone, and that exercise may have some therapeutic benefit to patients with narcolepsy, a disorder caused by Hcrt/Ox deficiency. Acute changes in body temperature may facilitate prediction of cataplexy onset and lead to interventions to mitigate its occurrence.

An analgesic pathway from parvocellular oxytocin neurons to the periaqueductal gray in rats

The hypothalamic neuropeptide oxytocin (OT) exerts prominent analgesic effects via central and peripheral action. However, the precise analgesic pathways recruited by OT are largely elusive. Here we discovered a subset of OT neurons whose projections preferentially terminate on OT receptor (OTR)-expressing neurons in the ventrolateral periaqueductal gray (vlPAG). Using a newly generated line of transgenic rats (OTR-IRES-Cre), we determined that most of the vlPAG OTR expressing cells targeted by OT projections are GABAergic. Ex vivo stimulation of parvocellular OT axons in the vlPAG induced local OT release, as measured with OT sensor GRAB. In vivo, optogenetically-evoked axonal OT release in the vlPAG of as well as chemogenetic activation of OTR vlPAG neurons resulted in a long-lasting increase of vlPAG neuronal activity. This lead to an indirect suppression of sensory neuron activity in the spinal cord and strong analgesia in both female and male rats. Altogether, we describe an OT-vlPAG-spinal cord circuit that is critical for analgesia in both inflammatory and neuropathic pain models.

The Role of Oxytocin and Vasopressin in Drug-Induced Reward-Implications for Social and Non-Social Factors.

Drug abuse is a worldwide problem that leads to negative physical, mental, and economic consequences. Although pharmacological strategies for drug addiction management have been widely studied, therapeutic options with high efficacy and a low side-effects profile are still limited. Recently, there has been a growing interest in oxytocin (OT) and vasopressin (AVP) systems as potential therapeutic targets for the treatment of drug abuse. OT and AVP are hypothalamic neuropeptides involved in numerous physiological processes. Additionally, studies show that these neurohormones are highly implicated in the modulation of a wide range of behaviors. Interestingly, ample evidence has shown that both, OT and AVP are able to decrease the consumption of different drugs of abuse, as well as to ameliorate their rewarding and reinforcing effects. Furthermore, OT and AVP have been strongly involved in prosocial effects and social reward. In particular, OT has been shown to be able to shift drug-induced reward into social-induced reward, mainly due to its interaction with the dopaminergic system. This phenomenon is also reflected in the results of clinical trials where intranasal OT shows promising efficacy in managing substance use disorder. Therefore, the aim of this review is to comprehensively characterize the involvement of OT and AVP in the rewarding and other behavioral effects of drugs of abuse in animal models, with a particular highlight on the impact of social factors on the observed effects. Understanding this relationship may contribute to higher drug development success rates, as a result of a more profound and deliberate studies design.

Does kisspeptin exert a local modulatory effect on bovine ovarian steroidogenesis?

Kisspeptin, a hypothalamic neuropeptide encoded by the KISS1 gene, has a pivotal role in promoting GnRH secretion in mammals. Kisspeptin and its receptor (KISS1R) are also expressed in certain peripheral tissues including gonads, suggesting intra-gonadal roles. Such actions at the level of the bovine ovary have not been explored previously. The current aims were to determine whether KISS1 and its receptor (KISS1R) are expressed in the bovine ovary and whether kisspeptin or a kisspeptin antagonist can modulate ovarian steroid production by cultured ovarian cells. Granulosa (GC) and theca interna (TC) were collected from antral follicles (3-18 mm) categorized into five class sizes. Early, mid and regressing corpora lutea (CL) were also collected for RT-qPCR analysis of KISS1 and KISS1R expression. Bovine TC and GC cultured under both non-luteinizing (serum-free) and luteinizing (serum-supplemented) conditions were treated for 4 days with kisspeptin-10 (10-10-10-6M) or kisspeptin antagonist (p234; 10-10-10-6M), alone and in combination with either FSH (GC), LH (TC) or forskolin (luteinized GC/TC). Steroid secretion (GC: oestradiol, progesterone; TC: androstenedione, progesterone; luteinized GC/TC: progesterone) was measured by ELISA and viable cell number determined by neutral red uptake assay. KISS1 and KISS1R transcripts were detected in TC, GC and CL with significant differences between follicle categories and CL stages. However, neither kisspeptin-10 nor kisspeptin antagonist affected steroid secretion or viable cell number in any of the four ovarian cell culture models. As such, the hypothesis that kisspeptin has a direct intra-ovarian role to modulate follicular or luteal steroidogenesis, or cell proliferation/survival, is not supported.

Blood Levels of Neuropeptide 26RFa in Relation to Anxiety and Aggressive Behavior in Humans—An Exploratory Study

26RFa, also referred to as QRFP, is a hypothalamic neuropeptide mainly known for its role in the regulation of appetite and glucose metabolism. Its possible relevance to emotional regulation is largely unexplored. To address this, in the present exploratory study, we analyzed the plasma concentrations of 26RFa in humans characterized by different levels of anxiety and aggressive behavior. For this purpose, the study included 13 prison inmates who have committed violent crimes and 19 age-matched healthy men from the general population as controls. Anxiety, depression and aggressive behavior were evaluated in both groups using standard questionnaires. The inmate group was characterized by increased aggression and anxiety compared to the controls. We found that the mean plasma levels of 26RFa did not significantly differ between the inmates and the controls. However, several high outliers were present only in the inmate group. The plasma levels of 26RFa correlated positively with the anxiety scores in all the studied subjects and controls. After removing the high outliers in the inmate group, positive correlations of 26RFa with anxiety and a subscale of hostility in the aggression scale were also recorded in this group. No significant correlations of 26RFa with depression scores or other parameters of aggressive behavior were found. Thus, the present results did not support an involvement of 26RFa in aggressive behavior in humans but pointed to a link between this neuropeptide and anxiety. Nevertheless, considering the exploratory nature of the present study, this conclusion should be verified in a larger cohort, including the clinical degree of anxiety.