Activation of orexin-1 receptors in the amygdala enhances feeding in the diet-induced obesity rats: Blockade with µ-opioid antagonist.

Obesity has become a global problem due to its sharply increased prevalence and associated complications. Orexin and opioid signaling can regulate feeding behavior and represent potential therapeutic targets for obesity. In the present experiment, we sought to ascertain the effects of orexin-A and µ-opioid signaling regulation in the basomedial amygdala (BMA) on feeding and investigate the physiology of gastric distension (GD)-responsive neurons in a diet-induced obesity (DIO) and diet-induced obesity resistance (DR) rat model. Intra-BMA infusions of orexin-A increased the firing of BMA GD neurons and increased food intake, and that these effects could be abolished by pretreatment with the orexin-1 receptor (OX-1R) antagonist SB334867, these effects could also be somewhat attenuated by co-administration of naloxone. In the DIO and DR rats, mRNA expression of OX-1R and µ-opioid receptors were increased in the BMA. Our results strongly suggest that orexin-A and opioid signaling in the BMA play a major role in regulating GD neuronal excitability and feeding behavior in obesity.

Lateral hypothalamic Orexin-A-ergic projections to the arcuate nucleus modulate gastric function in vivo.

It has been well-known that hypothalamic orexigenic neuropeptides, orexin-A, and melanin-concentrating hormone (MCH), play important roles in regulation of gastric function. However, what neural pathway mediated by the two neuropeptides affects the gastric function remains unknown. In this study, by way of nucleic stimulation and extracellular recording of single unit electrophysiological properties, we found that electrically stimulating the lateral hypothalamic area (LH) or microinjection of orexin-A into the arcuate nucleus (ARC) excited most gastric distension-responsive neurons in the nuclei and enhanced the gastric function including motility, emptying, and acid secretion of conscious rats. The results indicated that LH-ARC orexin-A-ergic projections may exist and the orexin-A in the ARC affected afferent and efferent signal transmission between ARC and stomach. As expected, combination of retrograde tracing and immunohistochemistry showed that some orexin-A-ergic neurons projected from the LH to the ARC. In addition, microinjection of MCH and its receptor antagonist PMC-3881-PI into the ARC affected the role of orexin-A in the ARC, indicating a possible involvement of the MCH pathway in the orexin-A role. Our findings suggest that there was an orexin-A-ergic pathway between LH and ARC which participated in transmitting information between the central nuclei and the gastrointestinal tract and in regulating the gastric function of rats.

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 Effects ofNesfatin-1 in the Paraventricular Nucleus on Gastric Motility and Its Potential Regulation by the Lateral Hypothalamic Area in Rats / 现代生物医学进展

Objective: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).Methods:The projection of nerve ?ber and expression of nesfatin-1 were observed by retrograde tracing and fluo-immunohistochemistry staining;The nuclei microinjection and nuclei electrical stimulation,extracellular discharges of single unit neuron were used to observe the effects of nesfatin-1 on the GD neurons;Gastric motility recording in vivo were used to monitor the effects of nesfatin-1 on the amplitude of constriction and frequency of gastric motility in conscious rats.Results:Nesfatin-1 inhibited the majority of the GD-E neurons(1.97± 0.12 Hz vs.1.15± 0.07 Hz) and excited GD-I neurons (1.74± 0.10 Hz vs.3.04± 0.18 Hz) in the PVN,which were weakened by oxytocin receptor antagonist H4928 (GD-E:1.38± 0.08 Hz,P＜0.05 vs.nesfatin-1;GD-I:2.49± 0.15 Hz,P＜0.05 vs.nesfatin-1).Gastric motility experiments showed that administration ofnesfatin-1 in the PVN decreased 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 excited the firing rate of GD-responsive neurons (GD-E:2.06± 0.12 Hz vs.4.23± 0.21 Hz,GD-I:1.61± 0.09 Hz vs.4.83± 0.25 Hz) in the PVN.Pre-administration of an antinucleobindin-2/nesfatin-1 antibody in the PVN strengthened gastric motility,decreased GD-E neurons (1.74± 0.10 Hz vs.3.04± 0.18 Hz) and excited the discharging of the GD-I neurons(4.15± 0.18 Hz vs.4.83± 0.25) induced by electrical stimulation of the LHA.Conclusion:Nesfatin-1 in the PVN could serve as an inhibitory factor to inhibit gastric motility,which might be regulated by the LHA.

Nesfatin-1 Signaling in the Basom Edial Amygdala Modulates the Gastric Distension-sensitive Neurons Discharge and Decreases Gastric Motility by the Arcuate Nucleus / 现代生物医学进展

Objective:This study aimed to explore the effects ofnesfatin-1 on gastric distension (GD)-sensitive neurons in the basomedial amygdala (BMA) and the potential mechanism for nesfatin-1 to regulate gastric motility through the arcuate nucleus (Arc).Methods:The projection of nerve fiber and expression of nesfatin-1 were observed by retrograde tracing and fluo-immunohistochemistry staining;The nuclei microinjection and nuclei electrical stimulation,extracellular discharges of single unit neuron were used to observe the effects ofnesfatin-1 on the GD neurons;Gastric motility recording in vivo were used to monitor the effects ofnesfatin-1 on the amplitude of constriction and frequency of gastric motility in conscious rats.Results:NUCB2/Nesfatin-1/fluorogold-double labeled neurons were from ARC to BMA;Nesfatin-1 could excited the firing rate of most of the GD-E neurons (4.25± 1.02 Hz vs.5.32± 1.17 Hz,P＜0.01) and decreased the firing rate of most of the GD-I neurons (3.73± 0.92 Hz vs.2.64± 0.86 Hz,P＜0.01),inhibited the gastric motility,amplitude and frequency,SHU9119 could weaken the responses induced by nesfaton-1;Electrical stimulation of the Arc,the firing rate of nesfatin-1-induced GD-response neurons (GD-E:5.14± 1.32 Hz vs.6.75± 1.84 Hz,P＜0.05;GD-I:2.84± 0.86 Hz vs.4.05± 1.12 Hz,P ＜0.05) and the gastric amplitude and frequency were increase.Conclusion:It was suggested that nesfatin-1 in the BMA plays an important role in decreasing gastric motility and the Arc may be involved in this regulation process.

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.

Nesfatin-1 signaling in the basom edial amygdala modulates the gastric distension-sensitive neurons discharge and decreases gastric motility via melanocortin 3/4 receptors and modified by the arcuate nucleus.

Nesfatin-1 is a novel anorexigenic peptide that regulates feeding behavior and gastrointestinal function. This study aimed to explore the effects of nesfatin-1 on gastric distension (GD)-sensitive neurons in the basomedial amygdala (BMA) and the potential mechanism for nesfatin-1 to regulate gastric motility through the arcuate nucleus (Arc). The projection of nerve fiber and expression of nesfatin-1 were observed by retrograde tracing and fluo-immunohistochemistry staining. Single-unit discharges in the BMA were recorded extracellularly, and gastric motility in conscious rats was monitored. Results showed that the nesfatin-1/ fluorogold-double labeled neurons were observed in the Arc. Nesfatin-1 could excite the GD-excitatory neurons and inhibit the GD-inhibitory neurons in the BMA. Gastric motility and gastric emptying were significantly reduced by nesfatin-1 administration to the BMA in a dose-dependent manner. The effects of nesfatin-1 could be partially blocked by melanocortin 3/4 receptors antagonist, SHU9119. Electrical stimulation of the Arc significantly excited the response of GD neurons to nesfatin-1 and promoted gastric motility. Nevertheless, these effects could be mitigated by pretreatment with anti-NUCB2/nesfatin-1 antibody. It is suggested that nesfatin-1 in the BMA plays an important role in decreasing gastric motility and the Arc may be involved in this regulation process.

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.

Effects of exogenous nesfatin-1 on gastric distention-sensitive neurons in the central nucleus of the amygdala and gastric motility in rats.

Nesfatin-1 is a novel brain-gut peptide identified in several brain regions associated with feeding and gastrointestinal function. Our study explored the effects of nesfatin-1 in the central nucleus of the amygdala (CNA) on the activity of gastric distention (GD)-sensitive neurons, gastric motility, and the potential regulation mechanisms by the dorsal motor nucleus of the vagus (DMV). Following retrograde injection of fluorogold (FG) into the DMV, we found that nesfatin-1/FG dual-labeled neurons were detected in the CNA, which indicates that some of the nesfatin-1-immunoreactive neurons arising from the DMV may project to the CNA. Single unit discharges in the CNA were recorded extracellularly, and gastric motility was monitored by implantation of a force transducer into the stomach of conscious rats. These results showed that nesfatin-1 administration to the CNA excited most of the GD-excitatory neurons, inhibited GD-inhibitory neurons, and dose-dependently reduced gastric motility. All of the above effects induced by nesfatin-1 could be partially blocked by pretreatment with the melanocortin 3/4 receptors antagonist, SHU9119. Electrical stimulation of the DMV excited the majority of the nesfatin-1-responsive GD neurons in the CNA. Additionally, pretreatment with an anti-NUCB2/nesfatin-1 antibody in the CNA increased the firing rate of nesfatin-1-responsive GD-inhibitory neurons but decreased the firing rate in nesfatin-1-responsive GD-excitatory neurons following electrical stimulation of the DMV. Finally, a subdiaphragmatic vagotomy eliminated the diminished gastric motility induced by nesfatin-1 injection. Taken together, these findings suggest that nesfatin-1 regulates the activity of GD-sensitive neurons and gastric motility via the melanocortin pathway in the CNA. Furthermore, the DMV may be involved in this regulatory pathway.

Central nesfatin-1 influences the excitability of ghrelin-responsive gastric distension neurons in the arcuate nucleus and reduces gastric motility in rats.

Although the novel satiety peptide nesfatin-1 has been shown to regulate gastric motility, the underlying mechanisms have yet to be elucidated. The study aimed to explore the effects of nesfatin-1 on ghrelin-responsive gastric distension (GD) neurons in the arcuate nucleus (Arc), and potential regulation mechanisms of gastric motility by the paraventricular nucleus (PVN). Single-unit discharges in the Arc were recorded extracellularly, and gastric motility in conscious rats was monitored during the administration of nesfatin-1 to the Arc or electrical stimulation of the PVN. Retrograde tracing and fluo-immunohistochemistry staining were used to determine NUCB2/nesfatin-1 neuronal projections. Nesfatin-1 inhibited most of the ghrelin-responsive GD-excitatory neurons, but excited ghrelin-responsive GD-inhibitory neurons in the Arc. Gastric motility was significantly reduced by nesfatin-1 administration to the Arc in a dose-dependent manner. The firing activity in the Arc and changes to gastric motility were partly reduced by SHU9119, an antagonist of melanocortin 3/4 receptors. Electrical stimulation of PVN excited most of the ghrelin-responsive GD neurons in the Arc and promoted gastric motility. Nonetheless, pretreatment with an anti-NUCB2/nesfatin-1 antibody in the Arc further increased the firing rate of most of the ghrelin-responsive GD-excitatory neurons and decreased the ghrelin-responsive GD-inhibitory neurons following electrical stimulation of the PVN. Gastric motility was enhanced by pretreatment with an anti-NUCB2/nesfatin-1 antibody in the Arc following PVN stimulation. Furthermore, NUCB2/nesfatin-1/fluorogold double-labeled neurons were detected in the PVN. These results suggest that nesfatin-1 could serve as an inhibitory factor in the Arc to regulate gastric motility via the melanocortin pathway. The PVN could be involved in the regulation of the Arc in gastric activity.

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

Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor (GHS-R) pre-dominantly produced in the stomach. Recent studies have shown that it may promote food intake and gastric motility. We aim to explore effects of ghrelin on the gastric distension (GD) sensitive neurons and gastric motility in the lateral hypothalamic area (LHA), and the possible regulation by the lateral septum. Extracellular single unit discharges were recorded and the gastric motility was monitored by administration of ghrelin into LHA and electrical stimulation of lateral septum. Expression of GHS-R was determined by polymerase chain reaction (PCR), western blot and immunohistochemistry staining. Projection of nerve fiber and expression of ghrelin were observed by retrograde tracer and fluo-immunohistochemistry staining. Results revealed that there were GD neurons in the LHA, and administration of ghrelin could excite both GD-excitatory (GD-E) and GD-inhibited (GD-I) neurons in the LHA. The gastric motility was significantly promoted by administration of ghrelin into LHA with a dose dependent manner, which could be completely abolished by treatment with ghrelin receptor antagonist [D-Lys-3]-GHRP-6 or BIM-28163. c-Fos expression was significantly increased after ghrelin administration to the LHA. Electrical stimulation of the lateral septum could significantly excite GD neurons responsive to ghrelin in the LHA as well as promote gastric motility. However, those effects could be absorbed by pre-treatment of [D-Lys-3]-GHRP-6. GHSR-1a expression in the LHA had no change after ghrelin administration to the LHA or electrical stimulating lateral septum. Electrical lesion of the LHA resulted in the decrease of gastric motility. GHS-R and Ghrelin/FG-double labeled neurons were observed in the LHA and lateral septum, respectively. It is suggested that the LHA may involve in promoting gastric motility via ghrelin. The Lateral septum projects to the LHA and exerts some regulating function on the LHA.