Nasal application of kisspeptin-54 mitigates motor deficits by reducing nigrostriatal dopamine loss in hemiparkinsonian rats.

Parkinson's Disease is a progressive neurodegenerative disorder characterized by motor symptoms resulting from the loss of nigrostriatal dopaminergic neurons. Kisspeptins (KPs) are a family of neuropeptides that are encoded by the Kiss-1 gene, which exert their physiological effects through interaction with the GPR54 receptor. In the current investigation, we investigated the prospective protective effects of central KP-54 treatments on nigrostriatal dopaminergic neurons and consequent motor performance correlates in 6-hydroxydopamine (6-OHDA)-lesioned rats. Male adult Sprague Dawley rats underwent stereotaxic injection of 6-OHDA into the right medial forebrain bundle to induce hemiparkinsonism. Following surgery, rats received chronic central treatments of nasal or intracerebroventricular KP-54 (logarithmically increasing doses) for seven consecutive days. Motor performance was evaluated seven days post-surgery utilizing the open field test and catalepsy test. The levels of dopamine in the striatum were determined with mass spectrometry. Immunohistochemical analysis was conducted to assess the immunoreactivities of tyrosine hydroxylase (TH) and the GPR54 in the substantia nigra. The dose-response curve revealed a median effective dose value of ≈3 nmol/kg for both central injections. Due to its non-invasive and effective nature, nasal administration was utilized in the second phase of our study. Chronic administration of KP-54 (3nmol/kg, nasally) significantly protected 6-OHDA-induced motor deficits. Nasal KP-54 attenuated the loss of nigrostriatal dopaminergic neurons induced by 6-OHDA. Additionally, significant correlations were observed between motor performance and nigrostriatal dopamine levels. Immunohistochemical analysis demonstrated the localization of the GPR54 within TH-positive nigral cells. These findings suggest the potential efficacy of central KP-54 on motor impairments in hemiparkinsonism.

The role of hypothalamic Orexin-A in stress-induced gastric dysmotility: An agonistic interplay with corticotropin releasing factor.

BACKGROUND: Central Orexin-A (OXA) modulates gastrointestinal (GI) functions and stress response. This study aimed to investigate whether OXA and CRF interact at hypothalamic level. METHODS: Solid gastric emptying (GE), fecal output (FO), plasma corticosterone (CORT), and postprandial antro-pyloric motility were assessed in rats that underwent acute restraint stress (ARS) and pretreated with central OX1R and/or CRF receptor antagonists SB-334867 and alpha-helical CRF9,41 . Microdialysis was performed to assess ARS-induced release of OXA and CRF in PVN and LHA, respectively. Immunofluorescence labeling was performed to detect the stress-induced changes in OXA and to assess the hypothalamic distribution of OX1R and CRF1/2 receptors. ARS-induced c-Fos immunoreactivity was evaluated in PVN and LHA of rats received OX1R and CRF receptor antagonists. KEY RESULTS: ARS delayed GE by disturbing the coordination of antro-pyloric contractions while stimulating FO and CORT secretion. ARS-induced alterations in GE, FO, plasma CORT, and antro-pyloric motility were attenuated by OX1R and/or CRF receptor antagonists, however, these changes were completely restored in rats received both antagonists. ARS stimulated release of OXA and CRF which were significantly attenuated by α-CRF9,41 and SB-334867, respectively. The OX1R was detected in CRF-immunoreactive cells, whereas dense expression of CRF2 receptor but not CRF1 was observed in LHA. ARS remarkably increased OXA immunoreactivity in LHA. ARS-induced c-Fos expression in LHA and PVN was abolished by α-CRF9,41 and SB-334867, respectively. CONCLUSIONS & INFERENCES: Our findings suggest a reciprocal contribution of OXA and CRF which seems to be involved in the mediation of stress-induced alterations in neuroendocrine and GI motor functions.

Zinc (Zn) and adipose-derived mesenchymal stem cells (AD-MSCs) on MPTP-induced Parkinson's disease model: A comparative evaluation of behavioral and immunohistochemical results.

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons and sustained neuroinflammation due to microglial activation. Adipose tissue-derived mesenchymal stem cells (AD-MSCs) secrete neuroprotective factors to prevent neuronal damage. Furthermore, Zn regulates stem cell proliferation and differentiation and has immunomodulatory functions. Our in vivo study aimed to investigate whether Zn affects the activities of AD-MSCs in the MPTP-induced mouse model. Male C57BL/6 mice were randomly divided into six groups (n = 6): Control, Zn, PD, PD+Zn, PD+ (AD-MSC), PD+ (AD-MSC)+Zn. MPTP toxin (20 mg/kg) was dissolved in saline and intraperitoneally injected into experimental groups for two days with 12 h intervals. On the 3rd day, AD-MSCs were given to the right lateral ventricle of the PD+ (AD-MSC) and PD+ (AD-MSC)+Zn groups by stereotaxic surgery. Then, ZnSO4H2O was administered intraperitoneally for 4 days at 2 mg/kg. Seven days post MPTP injection, the motor activities of the mouse were evaluated. Then immunohistochemical analyzes were performed in SNpc. Our results showed that motor activity was lower in Group PD. AD-MSC and Zn administration have improved this impairment. MPTP caused a decrease in TH and BDNF expressions in dopaminergic neurons in Group PD. However, TH and BDNF expressions were more intense in the other groups. MCP-1, TGF-ß, and IL-10 expressions increased in administered groups compared to the Group PD. The present study indicates that Zn's individual and combined administration with AD-MSCs reduces neuronal damage in the MPTP-induced mouse model. In addition, anti-inflammatory responses that emerge with Zn and AD-MSCs may have a neuroprotective effect.

Adropin increases with swimming exercise and exerts a protective effect on the brain of aged rats.

Adropin is a protein in the brain that decreases with age. Exercise has a protective effect on the endothelium by increasing the level of adropin in circulation. In this study, whether adropin, whose level in the brain decreases with age, may increase with swimming exercise, and exhibit a protective effect was investigated. Young and aged male Sprague Dawley rats were submitted to 1 h of swimming exercise every day for 8 weeks. Motor activity parameters were recorded at the end of the exercise or waiting periods before the animals were euthanized. Increased motor functions were observed in only the young rats that exercised regularly. Adropin levels in the plasma, and the adropin and VEGFR2 immunoreactivities and p-Akt (Ser473) levels in the frontal cortex were significantly increased in the aged rats that exercised regularly. It was also observed that the BAX/Bcl2 ratio and ROS-RNS levels decreased, while the TAC levels increased in the aged rats that exercised regularly. The results of the study indicated that low-moderate chronic swimming exercise had protective effects by increasing the level of adropin in the frontal cortex tissues of the aged rats. Adropin is thought to achieve this effect by increasing the VEGFR2 expression level and causing Akt (Ser473) phosphorylation. These results indicated that an exercise-mediated increase in endogenous adropin may be effective in preventing the destructive effects of aging on the brain.

The influence of early-life and adulthood stressors on brain neuropeptide-S system.

Central administered neuropeptide-S (NPS) was shown to reduce stress response in rodents. This study aimed to investigate the alterations in NPS system upon chronic exposure to early-life and adulthood stressors. Newborn pups underwent maternal separation (MS) from postnatal day 1 to 14 comprised of daily 3-h separations. In the adulthood, 90-min of restraint stress was loaded to males as an acute stress (AS) model. For chronic homotypic stress (CHS), same stressor was applied for 5 consecutive days. The changes in the expression and the release of NPS were monitored by immunohistochemistry and microdialysis, respectively. Throughout the CHS, heart rate variability (HRV) was analyzed on a daily basis. The immunoreactivity for NPS receptor (NPSR) was detected in basolateral amygdala (BLA) and hypothalamic paraventricular nucleus (PVN) by immunofluorescence staining. The NPS expression in the brainstem was increased upon AS which was more prominent following CHS, whereas these responses were found to be blunted in MS counterparts. Similar to histological data, the stress-induced release of NPS in BLA was attenuated in MS rats. CHS-induced elevations in sympatho-vagal balance were alleviated in control rats; which was not observed in MS rats. The expression of NPSR in BLA and PVN was down-regulated in MS rats. The brain NPS/NPSR system appears to be susceptible to the early-life stressors and the subsequent chronic stress exposure in adulthood which results in altered autonomic outflow.

Centrally Administered Neuropeptide-S Alleviates Gastrointestinal Dysmotility Induced by Neonatal Maternal Separation.

BACKGROUND: Neuropeptide-S (NPS) regulates autonomic outflow, stress response, and gastrointestinal (GI) motor functions. This study aimed to investigate the effects of NPS on GI dysmotility induced by neonatal maternal separation (MS). METHODS: MS was conducted by isolating newborn pups from dams from postnatal day 1 to day 14. In adulthood, rats were also exposed to chronic homotypic stress (CHS). Visceral sensitivity was assessed by colorectal distension-induced abdominal contractions. Gastric emptying (GE) was measured following CHS, whereas fecal output was monitored daily. NPS or NPS receptor (NPSR) antagonist was centrally applied simultaneously with electrocardiography and gastric motility recording. Immunoreactivities for NPS, NPSR, corticotropin-releasing factor (CRF), choline acetyltransferase (ChAT), tyrosine hydroxylase (TH), and c-Fos were assessed by immunohistochemistry. KEY RESULTS: NPS alleviated the MS-induced visceral hypersensitivity. Under basal conditions, central exogenous or endogenous NPS had no effect on GE and gastric motility. NPS restored CHS-induced gastric and colonic dysmotility in MS rats while increasing sympatho-vagal balance without affecting vagal outflow. NPSR expression was detected in CRF-producing cells of hypothalamic paraventricular nucleus, and central amygdala, but not in Barrington's nucleus. Moreover, NPSR was present in ChAT-expressing neurons in dorsal motor nucleus of the vagus (DMV), and nucleus ambiguus (NAmb) in addition to the TH-positive neurons in C1/A1, and locus coeruleus (LC). Neurons adjacent to the adrenergic cells in LC were found to produce NPS. NPS administration caused c-Fos expression in C1/A1 cells, while no immunoreactivity was detected in DMV or NAmb. CONCLUSIONS: NPS/NPSR system might be a novel target for the treatment of stress-related GI dysmotility.

Effects of adropin on learning and memory in rats tested in the Morris water maze.

Adropin is a secreted peptide, which is composed of 43 amino acids and shows an effective role in regulating energy metabolism and insulin resistance. Motor coordination and locomotor activity were improved by adropin in the cerebellum. However, it is not known whether adropin administration has an effect on spatial learning and memory. In this study, we investigated the effect of adropin on spatial learning and memory and characterized the biochemical properties of adropin in the hippocampus. Thirty male Sprague-Dawley rats were randomly divided into two groups as control and adropin groups. The control group received 0.9% NaCl intracerebroventricular for 6 days, while the adropin groups received 1 nmol of adropin dissolved in 0.9% NaCl (for 6 days). The Morris water maze, Y maze, and object location recognition tests were performed to evaluate learning and memory. Also, the locomotor activity tests were measured to assess the motor function. The expression of Akt, phospho-Akt, CREB, phospho-CREB, Erk1/2, phospho-Erk1/2, glycogen synthase kinase 3 ß (GSK3ß), phospho-GSK3ß, brain-derived neurotrophic factor (BDNF), and N-methyl-d-aspartate receptor NR2B subunit were determined in the hippocampal tissues by using western blot. Behavior tests showed that adropin significantly increase spatial memory performance. Meanwhile, the western blot analyses revealed that the phosphorylated form of the Akt and CREB were enhanced with adropin administration in the hippocampus. Also, the expression of BDNF showed an enhancement in adropin group in comparison to the control group. In conclusion, we have shown for the first time that adropin exerts its enhancing effect on spatial memory capacity through Akt/CREB/BDNF signaling pathways.

Neuropeptide-S affects cognitive impairment and depression-like behavior on MPTP induced experimental mouse model of Parkinson's disease

Background/aim: The present study proposes to investigate the effect of neuropeptide­S (NPS) on cognitive functions and depression-like behavior of MPTP-induced experimental model of Parkinson's disease (PD). Materials and methods: Three-month-old C57BL/6 mice were randomly divided into three groups as; Control, Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and MPTP + NPS 0.1 nmol (received intraperitoneal injection of MPTP and intracerebroventricular injection of NPS, 0.1 nmol for seven days). The radial arm maze and pole tests were carried out, and the levels of tyrosine hydroxylase (TH) were determined using western blotting. A mass spectrometer was used to measure the levels of dopamine, glutamic acid, and glutamine. Results: The T-turn and time to descend enhanced in MPTP group, while these parameters were decreased by NPS treatment. In the MPTP group, the number of working memory errors (WME) and reference memory errors (RME) increased, whereas NPS administration decreased both parameters. Sucrose preference decreased in the MPTP group while increasing in the NPS group. MPTP injection significantly reduced dopamine, glutamic acid, and glutamine levels. NPS treatment restored the MPTP-induced reduction in glutamine and glutamic acid levels. Conclusion: NPS may be involved in the future treatment of cognitive impairments and depression-like behaviors in PD.

Sexual dimorphism in maternally separated rats: effects of repeated homotypic stress on gastrointestinal motor functions.

Experiencing stressful events during early life has been considered as a risk factor for development of functional gastrointestinal disorders in adulthood. This study aimed to investigate the sex-related differences in stress-induced gastrointestinal (GI) dysmotility in rats exposed to neonatal maternal separation (MS). Newborn pups were removed from mothers for 180 min from postnatal day-1 to day-14. Experiments were performed in male and female offsprings at adulthood. Elevated plus maze (EPM) test was used to assess MS-induced anxiety-like behaviors. Ninety minute of restraint stress was applied for once or 5 consecutive days for acute stress (AS) or repeated homotypic stress (RHS), respectively. Measurement of fecal output (FO) and gastric emptying (GE), and hypothalamic microdialysis were performed. Both in males and females, MS produced anxiety-like behaviors. AS delayed GE and increased FO in all groups. In RHS-loaded MS females, AS-induced alterations in GE and FO were restored, however, no adaptation was observed in male counterparts. Regardless of sex and neonatal stress experience, AS significantly increased corticotropin-releasing factor (CRF) release from paraventricular nucleus of hypothalamus, whereas females were found more susceptible than males. Following RHS, AS-induced elevations in CRF release were attenuated only in MS females, but not in males. Both females and males seem to be prone to AS-induced alterations in hypothalamic CRF system and in GI motor functions. Neonatal MS disturbs chronic stress coping mechanisms in males. Conversely, females are likely to circumvent the deleterious effects of neonatal MS on GI functions through developing a habituation to prolonged stressed conditions.

Sexual dimorphism in rats exposed to maternal high fat diet: alterations in medullary sympathetic network.

Exposure to high fat diet during perinatal period (PHFD) leads to neuroplastic changes in autonomic circuits, however, the role of gender has been incompletely understood. This study aims to investigate (i) short, and (ii) long-term effects of PHFD on autonomic outflow, and (iii) sexual dimorphic variations emerge at adulthood. Male and female rats were fed a control diet (13.5 % kcal from fat) or PHFD (60 % kcal from fat) from embryonic day-14 to postnatal day-21. To assess changes in autonomic outflow, heart rate variability (HRV) was analyzed at 10- and 20-week-old ages. Expressions of tyrosine hydroxylase (TH), metabotropic glutamate2/3 receptor (mGlu2/3R), N-methyl-D-aspartate1 receptor (NMDA1R), and gamma aminobutyric acidA receptor (GABAAR) were evaluated by immunohistochemistry. PHFD did not affect the body weight of 4-, 10-or 20-week-old male or female offsprings. PHFD significantly increased the sympathetic marker low frequency (LF) component, and sympatho-vagal balance (LF:HF) only in 10-week-old PHFD males. Compared with control, the propranolol-induced (4 mg·kg- 1, ip) decline in LF was observed more prominently in PHFD rats, however, these changes were found to be restored at the age of 20 weeks. In caudal ventrolateral medulla and nucleus tractus solitarius, expression of mGlu2/3R was downregulated in PHFD males, whereas no change was detected in NMDA1R. The number of GABAAR-expressing TH-immunoreactive cells was decreased in rostral ventrolateral medulla of PHFD males. The findings of this study suggest that exposure to maternal high-fat diet could lead to autonomic imbalance with increased sympathetic tone in the early adulthood of male offspring rats without developing obesity.

Protective mechanism of Syringic acid in an experimental model of Parkinson's disease.

6-Hydroxydopamine (6-OHDA) is a widely used chemical to model Parkinson's disease (PD) in rats. Syringic acid (SA) is a polyphenolic compound which has antioxidant and anti-inflammatory properties. The present study aimed to evaluate the neuroprotective role of SA in a rat model of 6-OHDA-induced PD. Parkinson's disease was created by injection of 6-OHDA into the medial forebrain bundle via stereotaxic surgery. Syringic acid was administered daily by oral gavage, before or after surgery. All groups were tested for locomotor activity, rotarod performance and catatony. Dopamine levels in SN were determined by an optimized multiple reaction monitoring method using ultra-fast liquid chromatography coupled with tandem mass spectrometry (MS/MS). The immunoreactivities for tyrosine hydroxylase (TH) and inducible nitric oxide synthase (iNOS) were detected by immunohistochemistry in frozen substantia nigra (SN) sections. Nitrite/nitrate levels, iNOS protein, total oxidant (TOS) and total antioxidant (TAS) status were assayed in SN tissue by standard kits. Motor dysfunction, impaired nigral dopamine release, increased iNOS expression and elevated nitrite/nitrate levels induced by 6-OHDA were significantly restored by SA treatment. Syringic acid significantly improved the loss of nigral TH-positive cells, while increasing TAS capacity and reducing TOS capacity in SN of PD rats. These data conclude that SA is a potential therapeutic agent for the treatment of 6-OHDA-induced rat model of PD. Syringic acid reduced the progression of PD via its neuroprotective, antioxidant and anti-inflammatory effects.

Neuropeptide-S prevents 6-OHDA-induced gastric dysmotility in rats.

This study aims to explore the effect of chronic central neuropeptide-S (NPS) treatment on gastrointestinal dysmotility and the changes of cholinergic neurons in the dorsal motor nucleus of the vagus (DMV) of a Parkinson's disease (PD) rat model. The PD model was induced through a unilateral medial forebrain bundle (MFB) administration of the 6-hydroxydopamine (6-OHDA). Locomotor activity (LMA), solid gastric emptying (GE), and gastrointestinal transit (GIT) were measured 7 days after the surgery. NPS was daily administered (1 nmol, icv, 7 days). In substantia nigra (SN), dorsal motor nucleus of the vagus (DMV), and gastric whole-mount samples, changes in tyrosine hydroxylase (TH), choline acetyltransferase (ChAT), neuronal nitric oxide synthase (nNOS), glial fibrillary acidic protein (GFAP), NPS receptor (NPSR), and alpha-synuclein (Ser129) were examined by immunohistochemistry. Cuprolinic blue staining was used to evaluate the number of neuronal cells in myenteric ganglia. The GIT rate, the total number of myenteric neurons, and the expressions of ChAT, nNOS, TH, and GFAP in the myenteric plexus were not changed in rats that received the 6-OHDA. Chronic NPS treatment reversed 6-OHDA-induced impairment of the motor performance, and GE, while preventing the loss of dopaminergic and cholinergic neurons in SN and DMV, respectively. NPS attenuated 6-OHDA-induced α-syn (Ser129) pathology both in SN and DMV. Additionally, expression of NPSR protein was detected in gastro-projecting cells in DMV. Taken together, centrally applied NPS seems to prevent 6-OHDA-induced gastric dysmotility through a neuroprotective action on central vagal circuitry.

The effect of chronic neuropeptide-S treatment on non-motor parameters in experimental model of Parkinson's disease.

AIM: Besides motor impairment, non-motor symptoms including cognitive decline, anxiety, and depression are observed in Parkinson's Disease (PD). The aim of this study was to investigate whether chronic administration of central neuropeptide-S (NPS) improves non-motor symptoms in 6-hydroxydopamine (6-OHDA)-induced parkinsonian rats. MATERIAL AND METHODS: Experimental PD was utilized by unilateral stereotaxic injection of the 6-OHDA into the medial forebrain bundle (MFB), while the sham-operated animals underwent the same surgical procedures. NPS (1 nmol) or vehicle was daily administered through an intracerebroventricular (icv) cannula for 7 days. Radial arm maze (RAM) test was used to evaluate the working memory; whereas, elevated plus maze (EPM) test and sucrose preference test were used to monitor the anxiety and depression status, respectively. The levels of dopamine, glutamic acid, and glutamine was determined in harvested striatal and hippocampal tissue samples. The immunoreactivities for tyrosine hydroxylase (TH) was determined using immunohistochemistry. RESULTS: In the RAM test, the 6-OHDA-induced increases in the reference and working memory errors were reduced by the central NPS administration. The decreased sucrose preference in the parkinsonian rats was increased by centrally administered NPS. The levels of dopamine levels in striatum and hippocampus were decreased in the parkinsonian rats, however, they were not altered by the centrally administered NPS. Additionally, NPS treatment significantly attenuated the 6-OHDA-induced loss of TH neuronal number. CONCLUSION: Consequently, NPS appears to be a therapeutic candidate for the treatment of non-motor complications of PD.

The role of autonomic pathways in peripheral apelin-induced gastrointestinal dysmotility: involvement of the circumventricular organs.

NEW FINDINGS: What is the central question of this study? Are central autonomic pathways and circumventricular organs involved in apelin-induced inhibition of gut motility? What is the main finding and its importance? Peripherally administered apelin-13 inhibits gastric and colonic motor functions through sympathetic and parasympathetic autonomic pathways, which seems to be partly mediated by the apelin receptor in circumventricular organs. ABSTRACT: Peripheral administration of apelin-13 has been shown to inhibit gastrointestinal (GI) motility, but the relevant mechanisms are incompletely understood. This study aimed to investigate (i) whether the apelin receptor (APJ) is expressed in circumventricular structures involved in autonomic functions, (ii) whether they are activated by peripherally administered apelin, (iii) the role of autonomic pathways in peripheral exogenous apelin-induced GI dysmotility, and (iv) the changes in apelin levels in the extracellular environment of the brain following its peripheral application. Ninety minutes after apelin-13 administration (300 µg kg-1 , i.p.), gastric emptying (GE) and colon transit (CT) were measured in rats that underwent parasympathectomy and/or sympathectomy. Plasma and cerebrospinal fluid (CSF) samples were also collected from another group of rats that received apelin-13 or vehicle injection. The immunoreactivities for APJ and c-Fos in circumventricular organs (CVOs) were evaluated by immunohistochemistry. Compared with vehicle-treated rats, GE and CT were inhibited significantly by apelin-13 treatment, and were completely restored in animals that underwent the combination of parasympathectomy and sympathectomy and sympathectomy alone, respectively. Apelin concentrations were elevated in both plasma and CSF following peripheral administration of apelin-13. APJ expression was detected in area postrema (AP), subfornical organ and organum vasculosum of lamina terminalis, and c-Fos expression was observed in response to apelin injection. Apelin-induced c-Fos expression in AP was partially attenuated by pretreatment with the cholecystokinin-1 receptor antagonist lorglumide, whereas it was completely abolished in vagotomized rats. The present data suggest that APJ in CVOs could indirectly contribute to the inhibitory action of peripheral apelin on GI motor functions.

Gastric motor dysfunction coincides with the onset of obesity in rats fed with high-fat diet.

Exposure to a high-fat diet (HFD) has been reported to impair central autonomic and enteric neurocircuitries, however, the relevant mechanisms and their time course are inadequately clarified. This study aimed to investigate the effects of HFD consumption through the period of adolescence on gastric motor functions in adulthood. Male Sprague-Dawley rats consumed a regular diet or HFD (60% kcal by fat) from 4 to 12 weeks of age. Body weight and food intake were monitored weekly. In adult rats, gastric emptying (GE) was measured. Additionally, using in-vitro organ bath, contractile and relaxant responses of antral and fundic strips were assessed with bethanechol and sodium nitroprusside (SNP), respectively. The expressions of choline acetyltransferase (ChAT), neuronal nitric oxide synthase (nNOS) and vasoactive intestinal polypeptide (VIP) were detected by immunofluorescence, whereas, the number of myenteric neurons were evaluated by staining with cuprolinic blue and enteric neuronal marker PGP 9.5. In adulthood, the HFD did not alter food intake, while significantly increasing the body weight. In HFD-fed adult rats, increased visceral fat mass was accompanied by delayed GE. Moreover, bethanechol- and SNP-induced responses were attenuated in antral and fundic tissues. HFD remarkably decreased the number of myenteric neurons and NOS immunoreactivity both in fundus and antrum. HFD remarkably decreased ChAT expression, while increasing the immunoreactivity for VIP in antrum. In conclusion, consumption of HFD between early adolescence and adulthood results in obesity and impairment of gastric motor functions. Particularly, HFD-induced gastric dysmotility appears to be predominantly dependent on the modifications in the non-adrenergic non-cholinergic inhibitory neurotransmission.

Central neuropeptide-S administration alleviates stress-induced impairment of gastric motor functions through orexin-A.

BACKGROUND/AIMS: The novel brain peptide neuropeptide-S (NPS) is produced exclusively by a small group of cells adjacent to the noradrenergic locus coeruleus. The NPSR mRNA has been detected in several brain areas involved in stress response and autonomic outflow, such as amygdala and hypothalamus, suggesting that central NPS may play a regulatory role in stress-induced changes in gastrointestinal (GI) motor functions. In rodents, exogenous central NPS was shown to inhibit stress-stimulated fecal output. Moreover, exogenous NPS was demonstrated to activate hypothalamic neurons that produce orexin-A (OXA), which has been shown to stimulate postprandial gastric motor functions via central vagal pathways. Therefore, we tested whether OXA mediates the NPS-induced alterations in gastric motor functions under stressed conditions. MATERIALS AND METHODS: We investigated the effect of central exogenous NPS on solid gastric emptying (GE) and gastric postprandial motility in acute restraint stress (ARS)-loaded conscious rats. The OXA receptor antagonist SB-334867 was administered centrally prior to the central NPS injection. The expression of NPSR in the hypothalamus and dorsal vagal complex was analyzed by immunofluorescence. RESULTS: Central administration of NPS restored the ARS-induced delayed GE and uncoordinated postprandial antro-pyloric contractions. The alleviative effect of NPS on GE was abolished by pretreatment of the OX1R antagonist SB-334867. In addition to hypothalamus, NPSR was detected in the dorsal motor nucleus of vagus, which suggest a direct stimulatory action of exogenous NPS on gastric motility. CONCLUSION: NPS may be a novel candidate for the treatment of stress-related gastric disorders.

Enteric apelin enhances the stress-induced stimulation of colonic motor functions.

In response to stress, apelin and corticotropin-releasing factor (CRF) are upregulated in the gastrointestinal (GI) tract. This study was designed to investigate the effect of stress on endogenous apelin in colon and its regulatory role on colonic motor functions. Colon transit (CT) was measured in rats exposed to acute restraint stress (ARS). APJ and CRF receptor antagonists F13A and astressin were administered intraperitoneally 30 min before ARS loading. Colonic muscle contractions were evaluated by in-vivo motility recording and in-vitro organ bath studies. Detection of apelin or CRF was performed using immunohistochemistry in proximal and distal colon of non-stressed (NS) and ARS-loaded rats. Immunoreactivity of CRF1 with apelin or APJ receptor was detected with double-labeled immunofluorescence in colonic myenteric neurons. Compared with NS rats, ARS accelerated the CT which was attenuated significantly by F13A or astressin. Following ARS, the expression of CRF was increased remarkably in distal colon, while the stress-induced change was not prominent in proximal colon. Apelin-positive cells were detected in myenteric ganglia of distal colon, while no apelin immunoreactivity observed in myenteric neurons of proximal colon. Both apelin and APJ receptor are colocalized with CRF1 in myenteric neurons of distal colon. In the in-vivo colonic motility experiments, apelin-13 exhibited a rapid stimulatory effect. CRF administration increased the motility which was abolished by F13A. Apelin-induced contractions in muscle strips were no longer observed with preadministration of F13A. These results suggest that enteric apelin contributes to the action of CRF on colonic motor functions under stressed conditions.LAY SUMMARYIt has been suggested in rodents that acute stress increases the expression of apelin in gastrointestinal tissues. We have found that under stressed conditions, enteric apelin contributes to the CRF-induced alterations in colonic motor functions through APJ receptor.

Central neuropeptide-S treatment improves neurofunctions of 6-OHDA-induced Parkinsonian rats.

Parkinson's disease (PD) is characterized by degeneration of the dopaminergic neurons in substantia nigra (SN). The motor symptoms of PD include tremor, rigidity, bradykinesia and postural impairment. In rodents, central administration of neuropeptide-S (NPS) has been shown to induce locomotor activity, dopamine release and neuronal survival by decreasing lipid peroxidation, additionally, the NPS receptor (NPSR) was detected in SN. Accumulating findings suggest that central NPS may ameliorate the parkinsonian symptoms, however, this has been explored incompletely due to the scarcity of experimental studies. Therefore, the present study was designed to test whether central NPS treatment exerts protective and/or alleviative effects on 6-OHDA-induced rat experimental PD model. Adult male Wistar rats received acute (alleviate; 10 nmol, icv) or chronic (protective; 1 nmol, icv for 7 days) NPS treatment following the central injection of 6-OHDA in medial forebrain bundle. Motor performance tests and in vivo nigral microdialysis were performed before and 7 days after the central 6-OHDA injection. The immunoreactivities for tyrosine hydroxylase (TH), NPSR, 4-hydroxynonenal (4-HNE) and c-Fos were detected by immunohistochemistry in frozen SN sections. Our double immunofluorescence labeling studies demonstrated that NPSR is present in the nigral TH-positive neurons. Central NPS injection caused a remarkable c-Fos expression in SN; whereas, no change was observed following vehicle injection. In both chronic and acute treatment groups, the 6-OHDA-induced motor dysfunction and impaired nigral dopamine release were improved significantly. However, only chronic, but not acute treatment restored the loss of nigral TH-positive cells, while decreasing the 4-HNE immunoreactivity in SN. Our findings demonstrate that central NPS treatment not only exerts a neuroprotective action on nigral dopaminergic neurons, it also improves the striatal dopaminergic signaling. Therefore, the present study candidates the NPSR agonism as a novel therapeutic approach for PD treatment.

Acute restraint stress induces cholecystokinin release via enteric apelin.

Stress increases the apelin content in gut, while exogenous peripheral apelin has been shown to induce cholecystokinin (CCK) release. The present study was designed to elucidate (i) the effect of acute stress on enteric production of apelin and CCK, (ii) the role of APJ receptors in apelin-induced CCK release depending on the nutritional status. CCK levels were assayed in portal vein blood samples obtained from stressed (ARS) and non-stressed (NS) rats previously injected with APJ receptor antagonist F13A or vehicle. Duodenal expressions of apelin, CCK and APJ receptor were detected by immunohistochemistry. ARS increased the CCK release which was abolished by selective APJ receptor antagonist F13A. The stimulatory effect of ARS on CCK production was only observed in rats fed ad-libitum. Apelin and CCK expressions were upregulated by ARS. In addition to the duodenal I cells, APJ receptor was also detected in CCK-producing myenteric neurons. Enteric apelin appears to regulate the stress-induced changes in GI functions through CCK. Therefore, apelin/APJ receptor systems seem to be a therapeutic target for the treatment of stress-related gastrointestinal disorders.

Peripheral apelin mediates stress-induced alterations in gastrointestinal motor functions depending on the nutritional status.

Exposure to stress induces gastrointestinal (GI) dysmotility. In rodents, acute restraint stress (ARS) inhibits gastric emptying (GE) and intestinal transit (IT) via central and peripheral corticotropin-releasing factor (CRF)-mediated pathways. Peripherally administered apelin-13 was shown to inhibit GI motor functions; moreover, stress-induced upregulation of gastric apelin content was demonstrated in rats suggesting that peripheral apelin may mediate stress-induced alterations in GI motility. We investigated the role of endogenous peripheral apelin in stress-induced GI dysfunction. GE, IT and gastro-duodenal fasting motility were measured in non-stressed (NS), CRF-injected and ARS-loaded rats. CRF and apelin receptor antagonists astressin or F13A was administered before ARS or peripheral CRF injection. Apelin and APJ receptor expressions were determined using immunohistochemistry and quantified by qRT-PCR. Double immunofluorescence was performed for enteric neuronal apelin. GE and IT were delayed by CRF and ARS. ARS-induced changes were attenuated by F13A, whereas astressin was ineffective. CRF-induced alterations in GE and IT were restored completely by astressin, while they were diminished by F13A. Antral phase III-like contractions were disturbed following ARS which were preserved by preadministration of astressin, but not F13A. CRF impaired gastric and duodenal fasting contractions, while these changes were not altered by F13A. ARS increased apelin expression in stomach and duodenum. Apelin immunoreactivity was detected in mucosa, smooth muscles and myenteric plexi, whereas dense APJ receptor expression was observed within tunica muscularis. APJ receptor was downregulated in rats fasted overnight. These results suggest that enteric apelin acts as an inhibitor stress mediator in the postprandial state.