Involvements of the lateral hypothalamic area in gastric motility and its regulation by the lateral septum

Alteration of Neural Pathways and Its Implications in Alzheimer’s Disease

Alzheimer’s disease (AD) is a neurodegenerative disease accompanied by cognitive and behavioral symptoms. These AD-related manifestations result from the alteration of neural circuitry by aggregated forms of amyloid-β (Aβ) and hyperphosphorylated tau, which are neurotoxic. From a neuroscience perspective, identifying neural circuits that integrate various inputs and outputs to determine behaviors can provide insight into the principles of behavior. Therefore, it is crucial to understand the alterations in the neural circuits associated with AD-related behavioral and psychological symptoms. Interestingly, it is well known that the alteration of neural circuitry is prominent in the brains of patients with AD. Here, we selected specific regions in the AD brain that are associated with AD-related behavioral and psychological symptoms, and reviewed studies of healthy and altered efferent pathways to the target regions. Moreover, we propose that specific neural circuits that are altered in the AD brain can be potential targets for AD treatment. Furthermore, we provide therapeutic implications for targeting neuronal circuits through various therapeutic approaches and the appropriate timing of treatment for AD.

Therapeutic Effect and Mechanism of Acupuncture in Autoimmune Diseases

Autoimmune diseases (AIDs) are conditions arising from abnormal immune reactions to autoantigens, which can be defined as the loss of immune tolerance to autoantigens, causing the production of autoantibodies and subsequent inflammation and tissue injury. The etiology of AIDs remains elusive, which may involve both genetic and environmental factors, such as diet, drugs, and infections. Despite rapid progress in the treatment of autoimmune diseases over the past few decades, there is still no approach that can cure AIDs. As an alternative approach, traditional Chinese medicine (TCM) such as acupuncture has been used in an attempt to treat AIDs including multiple sclerosis (MS), rheumatoid arthritis (RA), and inflammatory bowel disease (IBD), and the results have proven to be quite promising, despite the fact that its mechanism is still not fully understood. In this review, the present knowledge regarding mechanisms of acupuncture in the treatment of AIDs has been summarized, and deeper insights will be provided in order to better understand how acupuncture may regulate immune responses during AIDs.

Lateral septum mu opioid receptors in stimulation of feeding

Stimulation of mu opioid receptors using drugs like morphine can increase eating when injected into multiple brain regions including the lateral septum (LS). The LS has been classically associated with reward, anxiety and fearful behaviors but more recently has also received attention with regard to control of feeding. To investigate the role of LS opioid receptors in feeding, we injected mu, delta, and kappa opioid receptor agonists and a mu specific receptor antagonist directly into the LS of rats. We expected that if feeding is mu receptor specific then only mu receptor agonists would increase feeding. We also hypothesized that mu receptor antagonists would suppress the feeding elicited by mu receptor agonists like morphine. Further, because the LS is densely populated with GABA receptors, we used the GABA_A receptor agonist muscimol to assess the effect of inhibition of LS neurons on feeding. Our results show that the mu receptor agonist morphine and the specific mu agonist DAMGO reliably and significantly increase feeding behavior across doses tested, while delta and kappa agonists were ineffective. CTAP, a specific mu receptor antagonist, at low doses unexpectedly increased morphine-elicited feeding but at high doses decreased morphine's effect, consistent with mediation by mu receptors. Finally, muscimol rapidly elicited feeding, suggesting a role for LS GABA_A receptors in feeding stimulation. These findings suggest that mu opioid receptors in the LS play complex roles in feeding and that neural inhibition may be a mechanism by which they elicit feeding.

Routing of Hippocampal Ripples to Subcortical Structures via the Lateral Septum

The mnemonic functions of hippocampal sharp wave ripples (SPW-Rs) have been studied extensively. Because hippocampal outputs affect not only cortical but also subcortical targets, we examined the impact of SPW-Rs on the firing patterns of lateral septal (LS) neurons in behaving rats. A large fraction of SPW-Rs were temporally locked to high-frequency oscillations (HFOs) (120-180 Hz) in LS, with strongest coupling during non-rapid eye movement (NREM) sleep, followed by waking immobility. However, coherence and spike-local field potential (LFP) coupling between the two structures were low, suggesting that HFOs are generated locally within the LS GABAergic population. This hypothesis was supported by optogenetic induction of HFOs in LS. Spiking of LS neurons was largely independent of the sequential order of spiking in SPW-Rs but instead correlated with the magnitude of excitatory synchrony of the hippocampal output. Thus, LS is strongly activated by SPW-Rs and may convey hippocampal population events to its hypothalamic and brainstem targets.

Lateral septum growth hormone secretagogue receptor affects food intake and motivation for sucrose reinforcement

The hormone ghrelin promotes eating and is widely considered to be a hunger signal. Ghrelin receptors, growth hormone secretagogue receptors (GHSRs), are found in a number of specific regions throughout the brain, including the lateral septum (LS), an area not traditionally associated with the control of feeding. Here we investigated whether GHSRs in the LS play a role in the control of food intake. We examined the feeding effects of ghrelin and the GHSR antagonists ([d-Lys3]-growth hormone-releasing peptide-6 and JMV-2959) at doses subthreshold for effect when delivered to the lateral ventricle. Intra-LS ghrelin significantly increased chow intake during the midlight phase, suggesting that pharmacological activation of LS GHSRs promotes feeding. Conversely, GHSR antagonist delivered to the LS shortly before dark onset significantly reduced chow intake. These data support the hypothesis that exogenous and endogenous stimulation of GHSRs in the LS influence feeding. Ghrelin is known to affect motivation for food, and the dorsal subdivision of LS (dLS) has been shown to play a role in motivation. Thus, we investigated the role of dLS GHSRs in motivation for food reward by examining operant responding for sucrose on a progressive ratio (PR) schedule. Intra-dLS ghrelin increased PR responding for sucrose, whereas blockade of LS GHSRs did not affect responding in either a fed or fasted state. Together these findings for the first time substantiate the LS as a site of action for ghrelin signaling in the control of food intake.

Bidirectional brain-gut interactions: Involvement of noradrenergic transmission within the ventral part of the bed nucleus of the stria terminalis

Introduction

Although the important roles of bidirectional interactions between the brain and gut in stress and emotional responses have long been recognized, the underlying neuronal mechanisms remain unclear. The bed nucleus of the stria terminalis (BNST) is a limbic structure involved in stress responses and negative affective states, such as anxiety and depression. We have previously demonstrated that noradrenergic transmission within the ventral part of the BNST (vBNST) plays a crucial role in anxiety‐like behaviors and pain‐induced aversion.

Objectives

This study aimed to examine the involvement of noradrenergic transmission via β‐adrenoceptors within the vBNST in bidirectional brain‐gut interactions.

Methods

We measured the gastric distention (GD)‐induced noradrenaline release within the vBNST of freely moving rats using an in vivo microdialysis technique. Gastric emptying and intestinal transit were examined following intra‐vBNST injections of isoproterenol, a β‐adrenoceptor agonist, in the absence or presence of the coadministration of timolol, a β‐adrenoceptor antagonist.

Results

Gastric distention at a higher pressure (45 mm Hg) but not at a lower pressure (25 mm Hg) resulted in a significant increase in extracellular noradrenaline levels within the vBNST. Intra‐vBNST injections of isoproterenol (30 nmol/side) induced significant reductions in gastric emptying and small intestinal transit, both of which were reversed by the coadministration of timolol (30 nmol/side).

Conclusion

Noradrenergic transmission via β‐adrenoceptors within the vBNST was involved in bidirectional brain‐gut interactions. These findings suggest that gastric dysfunction may induce negative affective states via the enhanced release of noradrenaline within the vBNST which, in turn, may cause gastrointestinal impairments.

In vivo microdialysis experiments demonstrated that gastric distention induced an increase in noradrenaline release within the vBNST. Intra‐vBNST injections of isoproterenol, a β‐adrenoceptor agonist, reduced gastric emptying and small intestinal transit, and these reducing effects were reversed by the coadministration of timolol, a β‐adrenoceptor antagonist. The present findings demonstrated important roles of noradrenergic transmission via β‐adrenoceptors within the vBNST in the bidirectional brain‐gut interactions.

Appetite suppressive role of medial septal glutamatergic neurons

Feeding behavior is controlled by diverse neurons and neural circuits primarily concentrated in the hypothalamus and hindbrain in mammals. In this study, by using chemo/optogenetic techniques along with feeding assays, we investigate how neurons within the medial septal complex (MSc), a brain area implicated in emotion and cognition, contribute to food intake. We find that chemo/optogenetic activation of MSc glutamatergic neurons profoundly reduces food intake during both light and dark periods of the rodent light cycle. Furthermore, we find that selective activation of MSc glutamatergic projections in paraventricular hypothalamus (PVH) reduces food intake, suggesting that MSc glutamatergic neurons suppress feeding by activating downstream neurons in the PVH. Open-field behavioral assays reveal that these neurons do not overtly affect anxiety levels and locomotion. Collectively, our findings demonstrate that septal glutamatergic neurons exert anorexigenic effects by projecting to the PVH without affecting anxiety and physical activities.

Ghrelin projection from the lateral hypothalamus area to the dorsal vagal complex and its regulation of gastric motility in cisplatin-treated rats

OBJECTIVE

To investigate ghrelin projection from the lateral hypothalamus area (LHA) to the dorsal vagal complex (DVC) and its regulation of gastric motility in cisplatin-treated rats.

MATERIALS AND METHODS

In the present study, the protein and mRNA expression of ghrelin and its receptor GHSR-1a were measured by Western blot and PCR, respectively. The ghrelin fiber projections arising from the LHA and projecting to the DVC were investigated by retrograde tracing combined with fluoro-immunohistochemical staining. The effects of ghrelin in the DVC, electrical stimulation of the LHA, and electrical lesion of the DVC on gastric motility were measured in cisplatin-treated rats.

RESULTS

Ghrelin fibers originating in the LHA projected to the DVC. The protein and mRNA expression of GHSR-1a was greater in cisplatin-treated rats than in saline-treated rats. Conversely, the expression of ghrelin in the LHA and DVC was reduced in cisplatin-treated rats. Cisplatin treatment also reduced gastric contractions. Ghrelin administrated into the DVC significantly promoted gastric motility, an effect completely blocked by treatment with the ghrelin receptor antagonist [D-Lys-3]-GHRP-6. In addition, electrical stimulation of the LHA promoted gastric motility, though this effect was much weaker in cisplatin-treated rats than in control rats. The excitatory effect of electrical stimulation of the LHA on gastric motility was partially blocked by pretreatment of the DVC with [D-Lys-3]-GHRP-6. Electrical lesion of the DVC diminished the excitatory effect that was induced by electrical stimulation of the LHA.

CONCLUSIONS

DVC, especially AP, may have a role for gastric contraction induced by the stimulation of the LHA. This regulation on gastric motility was weaker in cisplatin-treated rats than in saline-treated rats, possibly due to reduced ghrelin expression in the LHA and ghrelin projection from the LHA to the DVC.

Hippocampus Contributions to Food Intake Control: Mnemonic, Neuroanatomical, and Endocrine Mechanisms

Food intake is a complex behavior that can occur or cease to occur for a multitude of reasons. Decisions about where, when, what, and how much to eat are not merely reflexive responses to food-relevant stimuli or to changes in energy status. Rather, feeding behavior is modulated by various contextual factors and by previous experiences. The data reviewed here support the perspective that neurons in multiple hippocampal subregions constitute an important neural substrate linking the external context, the internal context, and mnemonic and cognitive information to control both appetitive and ingestive behavior. Feeding behavior is heavily influenced by hippocampal-dependent mnemonic functions, including episodic meal-related memories and conditional learned associations between food-related stimuli and postingestive consequences. These mnemonic processes are undoubtedly influenced by both external and internal factors relating to food availability, location, and physiological energy status. The afferent and efferent neuroanatomical connectivity of the subregions of the hippocampus is reviewed with regard to the integration of visuospatial and olfactory sensory information (the external context) with endocrine and gastrointestinal interoceptive stimuli (the internal context). Also discussed are recent findings demonstrating that peripherally derived endocrine signals act on receptors in hippocampal neurons to reduce (leptin, glucagon-like peptide-1) or increase (ghrelin) food intake and learned food reward-driven responding, thereby highlighting endocrine and neuropeptidergic signaling in hippocampal neurons as a novel substrate of importance in the higher-order regulation of feeding behavior.

Nesfatin-1 regulates the lateral hypothalamic area melanin-concentrating hormone-responsive gastric distension-sensitive neurons and gastric function via arcuate nucleus innervation

Nesfatin-1, a recently discovered neuropeptide involved in satiety. Recent studies have revealed that central nesfatin-1 inhibits gastric emptying and gastric acid secretion, though the mechanisms involved in these processes are not known. We aim to explore the effects of nesfatin-1 on a population of gastric distension (GD)-sensitive neurons in the lateral hypothalamus (LHA), gastric motility, and gastric secretion and the role for an arcuate nucleus (Arc)-LHA neural pathway in these processes. Single unit extracellular discharge recordings were made in of LHA. Further, gastric motility and gastric secretion in rats were monitored. Retrograde tracing and fluorescent immunohistochemical staining were used to explore nesfatin-1 neuron projection. The results revealed that administration of nesfatin-1 to the LHA or electric stimulation of the Arc could alter the neuronal activity of melanin-concentrating hormone (MCH)-responsive, GD-responsive neurons in LHA, which could be blocked by pretreatment with MCH receptor-1 antagonist PMC-3881-PI or weakened by pretreatment of a nesfatin-1 antibody in LHA. Administration of nesfatin-1 into LHA could inhibit gastric motility and gastric secretion, and these effects could be enhanced by administration of PMC-3881-PI. Electrical stimulation of Arc promoted the gastric motility and gastric secretion. Nesfatin-1 antibody or PMC-3881-PI pretreatment to LHA had no effect on Arc stimulation-induced gastric motility, but these pretreatments did alter Arc stimulation-induced effects on gastric secretion. Our findings suggest that nesfatin-1 signaling in LHA participates in the regulation of efferent information from the gastrointestinal tract and gastric secretion which also involve MCH signaling. Further, they show that a nesfatin-1-positive Arc to LHA pathway is critical for these effects.

Ghrelin fibers from lateral hypothalamus project to nucleus tractus solitaries and are involved in gastric motility regulation in cisplatin-treated rats

Ghrelin can alleviate cancer chemotherapy-induced dyspepsia in rodents, though the neural mechanisms involved are not known. Therefore, ghrelin projections from the lateral hypothalamus (LH) and its involvement in the regulation of gastric motility in cisplatin-treated rats were investigated with a multi-disciplined approach. Retrograde tracing combined with fluoro-immunohistochemical staining were used to investigate ghrelin fiber projections arising from LH and projecting to nucleus tractus solitaries (NTS). Results revealed that ghrelin fibers originating in LH project to NTS. Expression of ghrelin and its receptor growth hormone secretagogue receptor (GHS-R1a) in LH and NTS were detected by Western Blot. 2days after cisplatin dosing, expression of ghrelin in LH decreased while GHS-R1a in both LH and NTS increased. In electrophysiological experiments, the effects of N-methyl-d-aspartate (NMDA) microinjection in LH on neuronal discharge of gastric distension-responsive neurons in NTS and gastric motility were assessed. NMDA in LH excited most of ghrelin-responsive gastric distension (GD)-sensitive neurons in NTS and promoted gastric motility. This effect was partially blocked by ghrelin antibody in NTS. Furthermore, the excitatory effects of NMDA in cisplatin-treated rats were weaker than those in saline-treated rats. Behaviorally, cisplatin induced a significant increase of kaolin consumption and decrease of food intake. These studies reveal a decreased expression of ghrelin in LH and up-regulation of GHS-R1a in LH and NTS, which are involved in the regulation of GD neuronal discharge in NTS and gastric motility.

The Inhibitory Effects of Nesfatin-1 in Ventromedial Hypothalamus on Gastric Function and Its Regulation by Nucleus Accumbens

Aim: The aim of this study was to investigate the effect of nesfatin-1 signaling in the ventromedial hypothalamus (VMH) on gastric functions, as well as the regulation of these effects by nucleus accumbens (NAc) projections to VMH.

Methods: The expression of c-fos in nesfatinergic VMH neurons induced by gastric distension (GD) was measured using the double fluoro-immunohistochemical staining. The firing rates of neurons were monitored with single-unit extracellular electric discharge recording. The projection of nesfatinergic neurons from NAc to VMH was observed by fluorogold retrograde tracer combined with fluoro-immunohistochemical staining. The effect of nesfatin-1 in VMH or electric stimulation in NAc on gastric function was studied by measuring food intake, gastric acid output, gastric motility, and gastric emptying, and the ability of the melanocortin-3/4 receptor antagonist SHU9119 or the anti-nesfatin-1 antibody to block nesfatin-1 in the VMH was assessed.

Results: Expression of c-fos was observed in VMH nesfatinergic neurons following GD in rats. Further, nesfatin-1 delivery to single GD-responsive neurons changed the firing rates of these neurons in the VMH. In awake, behaving rats, intra-VMH administration of nesfatin-1 inhibited food intake, gastric acid output, gastric motility, and gastric emptying. These effects were abolished by SHU9119. Fluorogold retrograde tracing showed nesfatinergic neural projection from the NAc to the VMH. Electrical stimulation of NAc modified the firing rates of the VMH neurons and inhibited food intake and gastric functions. The pretreatment with an anti-nesfatin-1 antibody in the VMH reversed the effects of NAc electrical stimulation on the VMH neuronal firing rates and gastric function.

Conclusions: Nesfatin-1 in the VMH inhibited food intake, gastric acid output, gastric motility, and gastric emptying. A nesfatinergic pathway between NAc and VMH transmitted metabolism-regulating signals.

An Inhibitory Septum to Lateral Hypothalamus Circuit That Suppresses Feeding

Feeding behavior is orchestrated by neural circuits primarily residing in the hypothalamus and hindbrain. However, the relative influence of cognitive and emotional brain circuits to the feeding circuitry in the hypothalamus and hindbrain remains unclear. Here, using the cell-type selectivity of genetic methods, circuit mapping, and behavior assays, we sought to decipher neural circuits emanating from the septal nucleus to the lateral hypothalamus (LH) that contribute to neural regulation of food intake in mice. We found that chemogenetic and optogenetic activation of septal vesicular GABA transporter (vGAT)-containing neurons or their projections in the LH reduced food intake in mice. Consistently, chemogenetic inhibition of septal vGAT neurons increased food intake. Furthermore, we investigated a previously unknown neural circuit originating from septal vGAT neurons to a subset of vGAT neurons in the LH, an area involved in homeostatic and hedonic control of energy states. Collectively, our data reveal an inhibitory septohypothalamic feeding circuit that might serve as a therapeutic target for the treatment of eating disorders such as anorexia nervosa.

SIGNIFICANCE STATEMENT

Our results demonstrate that top-down projections from the septum to the hypothalamus control food intake negatively. Given the known role for both of these brain regions in the control of feeding and emotion-related behaviors, these findings reveal previously unknown neural circuitry that is likely implicated in emotional aspects of food intake and provide new insights into the development of therapeutic targets for the treatment of eating disorders.

Activity-Based Anorexia Reduces Body Weight without Inducing a Separate Food Intake Microstructure or Activity Phenotype in Female Rats-Mediation via an Activation of Distinct Brain Nuclei

Anorexia nervosa (AN) is accompanied by severe somatic and psychosocial complications. However, the underlying pathogenesis is poorly understood, treatment is challenging and often hampered by high relapse. Therefore, more basic research is needed to better understand the disease. Since hyperactivity often plays a role in AN, we characterized an animal model to mimic AN using restricted feeding and hyperactivity. Female Sprague-Dawley rats were divided into four groups: no activity/ad libitum feeding (ad libitum, AL, n = 9), activity/ad libitum feeding (activity, AC, n = 9), no activity/restricted feeding (RF, n = 12) and activity/restricted feeding (activity-based anorexia, ABA, n = 11). During the first week all rats were fed ad libitum, ABA and AC had access to a running wheel for 24 h/day. From week two ABA and RF only had access to food from 9:00 to 10:30 a.m. Body weight was assessed daily, activity and food intake monitored electronically, brain activation assessed using Fos immunohistochemistry at the end of the experiment. While during the first week no body weight differences were observed (p > 0.05), after food restriction RF rats showed a body weight decrease: −13% vs. day eight (p < 0.001) and vs. AC (−22%, p < 0.001) and AL (−26%, p < 0.001) that gained body weight (+10% and +13%, respectively; p < 0.001). ABA showed an additional body weight loss (−9%) compared to RF (p < 0.001) reaching a body weight loss of −22% during the 2-week restricted feeding period (p < 0.001). Food intake was greatly reduced in RF (−38%) and ABA (−41%) compared to AL (p < 0.001). Interestingly, no difference in 1.5-h food intake microstructure was observed between RF and ABA (p > 0.05). Similarly, the daily physical activity was not different between AC and ABA (p > 0.05). The investigation of Fos expression in the brain showed neuronal activation in several brain nuclei such as the supraoptic nucleus, arcuate nucleus, locus coeruleus and nucleus of the solitary tract of ABA compared to AL rats. In conclusion, ABA combining physical activity and restricted feeding likely represents a suited animal model for AN to study pathophysiological alterations and pharmacological treatment options. Nonetheless, cautious interpretation of the data is necessary since rats do not voluntarily reduce their body weight as observed in human AN.

Role of lateral septum glucagon-like peptide 1 receptors in food intake

Hindbrain glucagon-like peptide 1 (GLP-1) neurons project to numerous forebrain areas, including the lateral septum (LS). Using a fluorescently labeled GLP-1 receptor (GLP-1R) agonist, Exendin 4 (Ex4), we demonstrated GLP-1 receptor binding throughout the rat LS. We examined the feeding effects of Ex4 and the GLP-1R antagonist Exendin (9-39) (Ex9) at doses subthreshold for effect when delivered to the lateral ventricle. Intra-LS Ex4 suppressed overnight chow and high-fat diet (HFD) intake, and Ex9 increased chow and HFD intake relative to vehicle. During 2-h tests, intra-LS Ex9 significantly increased 0.25 M sucrose and 4% corn oil. Ex4 can cause nausea, but intra-LS administration of Ex4 did not induce pica. Furthermore, intra-LS Ex4 had no effect on anxiety-like behavior in the elevated plus maze. We investigated the role of LS GLP-1R in motivation for food by examining operant responding for sucrose on a progressive ratio (PR) schedule, with and without a nutrient preload to maximize GLP-1 neuron activation. The preload strongly suppressed PR responding, but blockade of GLP-1R in the intermediate subdivision of the LS did not affect motivation for sucrose under either load condition. The ability of the nutrient load to suppress subsequent chow intake was significantly attenuated by intermediate LS Ex9 treatment. By contrast, blockade of GLP-1R in the dorsal subdivision of the LS increased both PR responding and overnight chow intake. Together, these studies suggest that endogenous activity of GLP-1R in the LS influence feeding, and dLS GLP-1Rs, in particular, play a role in motivation.

Lateral hypothalamic area orexin-A influence the firing activity of gastric distension-sensitive neurons and gastric motility in rats

The orexins system consists of two G-protein coupled receptors (the orexin-1 and the orexin-2 receptor) and two neuropeptides, orexin-A and orexin-B. Orexin-A is an excitatory neuropeptide that regulates arousal, wakefulness and appetite. Recent studies have shown that orexin-A may promote gastric motility. We aim to explore the effects of orexin-A on the gastric -distension (GD) sensitive neurons and gastric motility in the lateral hypothalamic area (LHA), and the possible regulation by the paraventricular nucleus (PVN). Extracellular single unit discharges were recorded and the gastric motility was monitored by administration of orexin-A into the LHA and electrical stimulation of the PVN. There were GD neurons in the LHA, and administration of orexin-A to the LHA could increase the firing rate of both GD-excitatory (GD-E) and GD-inhibited (GD-I) neurons. The gastric motility was significantly enhanced by injection of orexin-A into the LHA with a dose dependent manner, which could be completely abolished by pre-treatment with orexin-A receptor antagonist SB334867. Electrical stimulation of the PVN could significantly increase the firing rate of GD neurons responsive to orexin-A in the LHA as well as promote gastric motility of rats. However, those effects could be partly blocked by pre-treatment with SB334867 in the LHA. It is suggested that orexin-A plays an important role in promoting gastric motility via LHA. The PVN may be involved in regulation of LHA on gastric motility.

Orexin-A affects gastric distention sensitive neurons in the hippocampus and gastric motility and regulation by the perifornical area in rats

Orexin-A is mainly produced in the lateral hypothalamus (LHA) and the perifornical area (PeF). Here, we aim to elucidate the effects of orexin-A in the hippocampus (Hi) on gastric distention (GD)-sensitive neurons and gastric motility, and potential regulation mechanisms by the PeF. Retrograde tracing and fluorescent-immunohistochemical staining were used to determine orexin-A neuronal projections. Single unit discharges in the Hi were recorded extracellularly and gastric motility in conscious rats was monitored during administration of orexin-A to the Hi or electrical stimulation of the PeF. Orexin-A administration to the Hi excited most of the GD-excitatory (GD-E) neurons and GD-inhibitory (GD-I) neurons, and increased gastric motility in a dose-dependent manner. All of effects induced by orexin-A could be partly blocked by pretreatment with orexin-A antagonist, SB-334867. Electrical stimulation of the PeF excited the majority of the orexin-A-responsive GD neurons in the Hi and promoted gastric motility. Additionally, pretreatment with SB-334867 in the Hi increased the firing rate of GDI and GDE neurons following electrical stimulation of the PeF. These findings suggest that orexin-A could regulate activities of GD-sensitive neurons and gastric motility. Furthermore, the PeF may be involved in this regulatory pathway.

Relationship between ghrelin and gastrointestinal diseases

Ghrelin is a newly found 28-amino acid brain-gut peptide, which is mainly secreted by the gastric mucosa. It has two forms, acyl-ghrelin and des-acyl ghrelin, and the former is the major active form. Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor and plays an important role in regulating food intake, gastric acid secretion, gastrointestinal motility, gastric mucosa protection, and inhibition of inflammatory reaction in paracrine, autocrine and endocrine manners. Recent studies have found that ghrelin levels are abnormal in a variety of gastrointestinal diseases, such as Helicobacter pylori infection, peptic ulcer, functional dyspepsia, inflammatory bowel disease, pancreatitis, tumors and so on, suggesting that ghrelin may be involved in the pathogenesis of these diseases. Ghrelin may become an index for disease diagnosis and prognosis evaluation and a new target for treatment of gastrointestinal diseases.

The effects of nesfatin-1 in the paraventricular nucleus on gastric motility and its potential regulation by the lateral hypothalamic area in rats

The current study investigated the effects of nesfatin-1 in the hypothalamic paraventricular nucleus (PVN) on gastric motility and the regulation of the lateral hypothalamic area (LHA). Using single unit recordings in the PVN, we show that nesfatin-1 inhibited the majority of the gastric distention (GD)-excitatory neurons and excited more than half of the GD-inhibitory (GD-I) neurons in the PVN, which were weakened by oxytocin receptor antagonist H4928. Gastric motility experiments showed that administration of nesfatin-1 in the PVN decreased gastric motility, which was also partly prevented by H4928. The nesfatin-1 concentration producing a half-maximal response (EC50) in the PVN was lower than the value in the dorsomedial hypothalamic nucleus, while nesfatin-1 in the reuniens thalamic nucleus had no effect on gastric motility. Retrograde tracing and immunofluorescent staining showed that nucleobindin-2/nesfatin-1 and fluorogold double-labeled neurons were observed in the LHA. Electrical LHA stimulation changed the firing rate of GD-responsive neurons in the PVN. Pre-administration of an anti- nucleobindin-2/nesfatin-1 antibody in the PVN strengthened gastric motility and decreased the discharging of the GD-I neurons induced by electrical stimulation of the LHA. These results demonstrate that nesfatin-1 in the PVN could serve as an inhibitory factor to inhibit gastric motility, which might be regulated by the LHA.