Functional dissection of parabrachial substrates in processing nociceptive information

Painful stimuli elicit first-line reflexive defensive reactions and,in many cases,also evoke second-line recuperative behaviors,the latter of which reflects the sensing of tissue damage and the alleviation of suffering.The lateral parabrachial nucleus(lPBN),composed of external-(elPBN),dorsal-(dlPBN),and central/superior-subnuclei(jointly referred to as slPBN),receives sensory inputs from spinal projection neurons and plays important roles in processing affective information from external threats and body integrity disruption.However,the organizational rules of lPBN neurons that provoke diverse behaviors in response to different painful stimuli from cutaneous and deep tissues remain unclear.In this study,we used region-specific neuronal depletion or silencing approaches combined with a battery of behavioral assays to show that slPBN neurons expressing substance P receptor(NK1R)(lPBNNK1R)are crucial for driving pain-associated self-care behaviors evoked by sustained noxious thermal and mechanical stimuli applied to skin or bone/muscle,while elPBN neurons are dispensable for driving such reactions.Notably,lPBNNK1R neurons are specifically required for forming sustained somatic pain-induced negative teaching signals and aversive memory but are not necessary for fear-learning or escape behaviors elicited by external threats.Lastly,both lPBNNK1R and elPBN neurons contribute to chemical irritant-induced nocifensive reactions.Our results reveal the functional organization of parabrachial substrates that drive distinct behavioral outcomes in response to sustained pain versus external danger under physiological conditions.

Substance P promotes epidural fibrosis via induction of type 2 macrophages

In response to spinal surgery,neurons secrete a large amount of substance P into the epidural area.Substance P is involved in macrophage differentiation and fibrotic disease.However,the specific roles and mechanisms of substance P in epidural fibrosis remain unclear.In this study,we established a mouse model of L1–L3 laminectomy and found that dorsal root ganglion neurons and the macrophages infiltrating into the wound area released sphingolipids.In vitro experiments revealed that type 1 macrophages secreted substance P,which promoted differentiation of type 1 macrophages towards a type 2 phenotype.High-throughput mRNA-seq analysis revealed that the sphingolipid metabolic pathway may be involved in the regulation of type 2 macrophages by substance P.Specifically,sphingomyelin synthase 2,a component of the sphingolipid metabolic pathway,promoted M2 differentiation in substance P-treated macrophages,while treating the macrophages with LY93,a sphingomyelin synthase 2 inhibitor,suppressed M2 differentiation.In addition,substance P promoted the formation of neutrophil extracellular traps,which further boosted M2 differentiation.Blocking substance P with the neurokinin receptor 1 inhibitor RP67580 decreased the number of M2 macrophages in the wound area after spinal surgery and alleviated epidural fibrosis,as evidenced by decreased fibronectin,α-smooth muscle actin,and collagen I in the scar tissue.These results demonstrated that substance P promotes M2 macrophage differentiation in epidural fibrosis via sphingomyelin synthase 2 and neutrophil extracellular traps.These findings provide a novel strategy for the treatment of epidural fibrosis.

Regulatory effect of nerve growth factor on release of substance P in cultured dorsal root ganglion neurons of rat

Objective To investigate the regulatory effects of nerve growth factor （NGF） on basal and capsaicin-induced release of neuropeptide substance P （SP） in primary cultured embryonic rat dorsal root ganglion （DRG） neurons. Methods DRGs were dissected from 15-day-old embryonic Wistar rats. DRG neurons were dissociated and cultured, and then exposed to different concentrations of NGF （10 ng/mL, 30 ng/mL, or 100 ng/mL） for 72 h. The neurons cultured in media without NGF served as control. RT-PCR were used for detecting the mRNAs of SP and vanilloid receptor 1 （VR1） in the DRG neurons. The SP basal and capsaicin （100 nmol/L）-induced release in the culture were measured by radioimmunoassay （RIA）. Results SP mRNA and VR1 mRNA expression increased in primary cultured DRG neurons in a dose-dependent manner of NGF. Both basal release and capsaicin-evoked release of SP increased in NGF-treated DRG neurons compared with in control group. The capsaicin-evoked release of SP also increased in a dose-dependent manner of NGF. Conclusion NGF may promote both basal release and capsaicin-evoked release of SP. NGF might increase the sensitivity of nociceptors by increasing the SP mRNA or VR1 mRNA.

Serotonin样,Substance P样,Enkephalin样反应阳性神经元胞体在大鼠中缝核簇内的分布

本文用PAP法研究了Serotonin样,Substance P样,Leucine—Enkephalin样和Methionine—Enkephalin样反应阳性神经元胞体在大鼠中缝核簇内的分布。证明Serotonin存在于中缝苍白核、中缝隐核、中缝大核、中缝桥核、中央上核和中缝背核等处的某些神经元胞体内。以中、小细胞为主,在中缝大核内有少数大细胞。细胞形态为梭形、圆形、卵圆形以及多极细胞。Substance P样反应阳性胞体在上述中缝核内也被发现,其胞体的大小、形态和分布与serotonin样反应阳性胞体相似,但数目稍少。Leucine—Enkephalin样反应阳性胞体存在于中缝苍白核、中缝隐核、中缝大核、中缝桥核、中缝背核和中央上核内,但Methionine—Enkephalin样反应阳性细胞体仅在中缝苍白核和中缝隐核的吻侧部以及中缝大核内发现。后两者均以大,中型多极细胞为主。

Effect of electro-acupuncture on substance P, its receptor and corticotropin-releasing hormone in rats with irritable bowel syndrome

AIM： To investigate the effect and mechanism of electro-acupuncture lEA） at ST25 and ST37 on irritable bowel syndrome （IBS） of rats. METHODS： A total of 21 male Sprague-Dawley rats were randomly divided into normal group, model group and EA group. A rat model of IBS was established by constraining the limbs and distending the colorectum of rats. Rats in EA group received bilateral EA at ST25 and ST37 with a sparse and intense waveform at a frequency of 2/50 Hz for 15 min, once a day for 7 d as a course. Rats in normal and model groups were stimulated by distending colorectum （CR）. An abdominal withdrawal reflex （AWR） scoring system was used to evaluate improvements in visceral hypersensitivity. Toluidine blue-improved method, immunohistochemistry and radioimmunoassay were used to observe mucosal mast cells （MC）, changes of substance P （SP） and substance P receptor （SPR） in colon and change of corticotropin-releasing hormone （CRH） in hypothalamus. RESULTS： The threshold of visceral sense was significantly lower in model group than in normal group,and significantly higher in EA group than in model group. The number of mucosal MC was greater in model group than in normal group and significantly smaller in EA group than in model group. The CRH level in hypothalamus of rats was significantly higher in model group than in normal group, which was remarkably decreased after electro-acupuncture treatment. The SP and SPR expression in colon of rats in model group was decreased after electro-acupuncture treatment. CONCLUSION： EA at ST25 and ST37 can decrease the number of mucosal MC and down-regulate the expression of CRH in hypothalamus, and the expression of SP and SPR in colon of rats with IBS.

Magnesium effects on behavior and substance P mRNA expression in the midbrain of a rat migraine model

BACKGROUND： Substance P participates in pain transmission and modulation, suggesting a close association with migraine headaches. The clinical application of magnesium has been effective in treating migraines, and the action mechanisms underlying migraines correlate with substance P expression. OBJECTIVE： To analyze different magnesium doses on behavior and substance P mRNA expression in the midbrain of a rat migraine model, and to determine the action pathway of migraine treatment using magnesium. DESIGN, TIME AND SETTING： A completely randomized, controlled, animal experiment was performed at the Experimental Animal Center and Central Laboratory in the Second Hospital of Jilin University between 2007 and 2008. MATERIALS： Magnesium sulfate （25%） was supplied by Tianjin Pharmaceutical Jiaozuo, China. Nitroglycerin was provided by Shanxi Kangbao Biological, China. Substance P primer sequence was synthesized by TaKaRa Biotechnology （Dalian）, China. METHODS： A total of 36 healthy, adult, Wistar rats were randomly assigned to 6 groups： control, migraine, low- and high-dose magnesium sulfate treated, and low- and high-dose magnesium sulfate control, with 6 rats in each group. Migraines were induced by subcutaneous injection of 10 mg/kg nitroglycerin in the migraine and low- and high-dose magnesium sulfate treated groups, and 2 mL/kg physiological saline was administered to rats in the control and low- and high-dose of magnesium sulfate control groups. Five minutes following administration, rats in low-dose groups were intraperitoneally injected with 100 mg/kg magnesium sulfate, while those in high-dose groups were injected with 300 mg/kg magnesium sulfate. No interventions were administered to the control and migraine groups. MAIN OUTCOME MEASURES： At 2 hours after nitroglycerin injection, substance P mRNA expression in the rat midbrain was measured by real-time quantitative polymerase chain reaction. At 60-90 minutes after nitroglycerin injection, behavioral changes of pain were analyzed in the experimental rats. RESULTS： The migraine group exhibited significantly lower levels of substance P mRNA expression compared with the control group （P 〈 0.05）. Following magnesium sulfate injection, substance P mRNA expression increased, compared with the migraine and control groups （P 〈 0.05）. In the low- and high-dose magnesium sulfate treated groups, pain behavior was remarkably ameliorated, compared with the migraine group （P 〈 0.05）, particularly with the high-dose injection （P 〈 0.05）. CONCLUSION： Magnesium relieved pain behaviors in a rat migraine model in a dose-dependent manner, and the therapeutic effect was achieved in conjunction with increased substance P expression in the midbrain.

Involvement of substance P and the NK-1 receptor in pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer related-death for both men and women and the 1-and5-year relative survival rates are 25%and 6%,respectively.Thus,it is urgent to investigate new antitumor drugs to improve the survival of pancreatic cancer patients.The peptide substance P(SP)has a widespread distribution throughout the body.After binding to the neurokinin-1(NK-1)receptor,SP regulates biological functions related to cancer,such as tumor cell proliferation,neoangiogenesis,the migration of tumor cells for invasion,infiltration and metastasis,and it exerts an antiapoptotic effects on tumor cells.It is known that the SP/NK-1 receptor system is involved in pancreatic cancer progression:(1)pancreatic cancer cells and samples express NK-1 receptors;(2)the NK-1 receptor is overexpressed in pancreatic cancer cells in comparison with non-tumor cells;(3)nanomolar concentrations of SP induce pancreatic cancer cell proliferation;(4)NK-1 receptor antagonists inhibit pancreatic cell proliferation in a concentration-dependent manner,at a certain concentration,these antagonists inhibit100%of tumor cells;(5)this antitumor action is medi-ated through the NK-1 receptor,and tumor cells die by apoptosis;and(6)NK-1 receptor antagonists inhibit angiogenesis in pancreatic cancer xenografts.All these data suggest that the SP/NK-1 receptor system could play an important role in the development of pancreatic cancer;that the NK-1 receptor could be a new promising therapeutic target in pancreatic cancer,and that NK-1 receptor antagonists could improve the treatment of pancreatic cancer.

Extracellular signal-regulated kinase, substance P and neurokinin-1 are involved in the analgesic mechanism of herb-partitioned moxibustion

Herb-partitioned moxibustion can effectively mitigate visceral pain, a major symptom in inflammatory bowel disease, but the analgesic lnechanism is still unclear. Moreover, extracellular signal-regulated kinase, substance P, and neurokinin-1 are involved in formation of central hyperalgesia. Thus, we postulated that the analgesic effect of herb-partitioned moxibustion may be associated with these factors. Accordingly, in this study, we established an inflammatory bowel disease visceral pain model in rat by enema with a mixed solution of 5% trinitrobenzenesulfonic acid and 50% ethanol. Bilateral Tianshu （ST25） and Qihai （CV6） points were selected for herb-partitioned moxi- bustion. Our results showed that herb-partitioned moxibustion improved visceral pain and down-regulated extracellular signal-regulated kinase, substance P, and neurokinin-1 protein and mRNA expression in dorsal root ganglia. These results indicate that down-regulation of extracellular signal-regulated kinase, substance E and neurokinin-1 protein and mRNA may be a central mechanism for the analgesic effect of herb-partitioned moxibustion.

PKCε Mediates Substance P Inhibition of GABA_A Receptors-Mediated Current in Rat Dorsal Root Ganglion

The mechanism underlying the modulatory effect of substance P（SP） on GABA-activated response in rat dorsal root ganglion（DRG） neurons was investigated. In freshly dissociated rat DRG neurons, whole-cell patch-clamp technique was used to record GABA-activated current and sharp electrode intracellular recording technique was used to record GABA-induced membrane depolarization. Application of GABA（1–1000 μmol/L） induced an inward current in a concentration-dependent manner in 114 out of 127 DRG neurons（89.8 %） examined with whole-cell patch-clamp recordings. Bath application of GABA（1–1000 μmol/L） evoked a depolarizing response in 236 out of 257（91.8%） DRG neurons examined with intracellular recordings. Application of SP（0.001–1 μmol/L） suppressed the GABA-activated inward current and membrane depolarization. The inhibitory effects were concentration-dependent and could be blocked by the selective neurokinin 1（NK1） receptors antagonist spantide but not by L659187 and SR142801（1 μmol/L, n=7）, selective antagonists of NK2 and NK3. The inhibitory effect of SP was significantly reduced by the calcium chelator BAPTA-AM, phospholipase C（PLC） inhibitor U73122, and PKC inhibitor chelerythrine, respectively. The PKA inhibitor H-89 did not affect the SP effect. Remarkably, the inhibitory effect of SP on GABA-activated current was nearly completely removed by a selective PKCε inhibitor epilon-V1-2 but not by safingol and LY333531, selective inhibitors of PKCα and PKCβ. Our results suggest that NK1 receptor mediates SP-induced inhibition of GABA-activated current and membrane depolarization by activating intracellular PLC-Ca2＋-PKCε cascade. SP might regulate the excitability of peripheral nociceptors through inhibition of the ＂pre-synaptic inhibition＂ evoked by GABA, which may explain its role in pain and neurogenic inflammation.

Substance P and its tachykinin NK1 receptor: a novel neuroprotective target for Parkinson's disease

Parkinson＇s disease （PD） is the most common motor neurode- generative disorder affecting approximately 4 million people worldwide. Although PD presents primarily with motor dysfunction, non-motor symptoms including cognitive decline, mood disorders, reduced olfaction and constipation are also of- ten present, with some of these non-motor symptoms even pre- senting prior to the onset of motor symptoms. It is well known that PD is largely caused by the gradual degeneration of dopa- minergic neurons within the substantia nigra pars compacta （SNc）, along with the presence of protein aggregates called Lewy bodies, which consist primarily of ct-synuclein and are found in the cytoplasm of surviving neurons. This ongoing cell loss and Lewy body pathology is not confined to the SNc, but is also seen in other brain regions implicated in PD pathogenesis such as the locus ceruleus.

Similar effects of substance P on learning and memory function between hippocampus and striatal marginal division

Substance P is an endogenous neurokinin that is present in the central and peripheral nervous systems. The neuropeptide substance P and its high-affinity receptor neurokinin 1 receptor are known to play an important role in the central nervous system in inflammation, blood pressure, motor behavior and anxiety. The effects of substance P in the hippocampus and the marginal di- vision of the striatum on memory remain poorly understood. Compared with the hippocampus as a control, immunofluorescence showed high expression of the substance P receptor, neuro- kinin 1, in the marginal division of the striatum of normal rats. Unilateral or bilateral injection of an antisense oligonucleotide against neurokinin 1 receptor mRNA in the rat hippocampus or marginal division of the striatum effectively reduced neurokinin 1 receptor expression. Indepen- dent of injection site, rats that received this antisense oligonucleotide showed obviously increased footshock times in a Y-maze test. These results indicate that the marginal division of the striatum plays a similar function in learning and memory to the hippocampus, which is a valuable addi- tion to our mechanistic understanding of the learning and memory functions of the marginal division of the striatum.

Substance P enhances the proliferation of rat anteriorpituitary cells in vitro

The undecapeptide substance P(SP) was shown to be intimately involved in both the structural and functional aspects of the anterior pituitary. Yet, in addition to its influences on hormonal secretion, SP may well possess more actions in this master gland. The present study was ftherefore aimed to investigate the effect of SP on the proliferation of rat anterior pituitary cells in primary culture. It was found that SP could dose-dependently increase the ineorporation of tritiated thymidine (3H-TdR)into cultured anterior pituitary cells. Other mammalian tachykinins such as neurokinin A and neurokinin B had similar effect but to varying degrees. The equipotent analogue of SP, Norleucine(11) -SP(Nle(11)-SP), also acted likewise, with its action antagonizable by spantide, a SP receptor blocker. To further characterize the nature of cells responsive to the challenge of SP, immunocytochemical staining against S-100 protein and some adenohypophyseal hormones was performed alone or plus autoradiography The results showed that the percentage of S-100 proteinimmunoreactive cells was apparently elevated by the addtion of Nle(11)-SP for 48 h, which indicates a preferential proliferation of folliculo-stellate cells under the regime. This was confirmed by increases in immunocytochemical or autoradiographical labelling indices of anterior pituitary cells treated similarly. Taken togethbr, these results reveal that the trophic action of SP observed previously in other tissues is also present at least in cultured rat anterior pituitary cells, with responding cells being predominantly folliculo-stellate cells as typified by S-100 proteinimmunoreactivity. Therefore, an intra-pituitary trophic action of SP in vivo could be anticipated.

EFFECT OF CAPSAICIN ON SUBSTANCE P IN PSORIASIS VULGARIS

Objective To the investigate the mechanism of capsaicin in psoriasis vulgaris. Methods Substance P(SP) in psoriatic lesions before and 6 weeks after the treatment with capsaicin was detedted by radioimmunoassary. Results After 3 weeks and 6 weeks treatment with capsaicin, SP in psoriatic lesions was decreased ( P <0.05), while it in the self control group was not decreased; Overall the efficient incidence in therapeutic group was 78.8% , while it in the control group was 36.8% . There was significant difference between them (χ 2 =16.30, P<0.001). Conclusion Capsaicin inhibits dermal inflammatory responses and proliferation of keratinocytes by decreasing the expression of SP in psoriasis vulgaris.

Substance P combined with epidermal stem cells promotes wound healing and nerve regeneration in diabetes mellitus

Exogenous substance P accelerates wound healing in diabetes,but the mechanism remains poorly understood.Here,we established a rat model by intraperitoneally injecting streptozotocin.Four wounds（1.8 cm diameter） were drilled using a self-made punch onto the back,bilateral to the vertebral column,and then treated using amniotic membrane with epidermal stem cells and/or substance P around and in the middle of the wounds.With the combined treatment the wound-healing rate was 100% at 14 days.With prolonged time,type I collagen content gradually increased,yet type III collagen content gradually diminished.Abundant protein gene product 9.5-and substance P-immunoreactive nerve fibers regenerated.Partial nerve fiber endings extended to the epidermis.The therapeutic effects of combined substance P and epidermal stem cells were better than with amniotic membrane and either factor alone.Our results suggest that the combination of substance P and epidermal stem cells effectively contributes to nerve regeneration and wound healing in diabetic rats.

Substance P mRNA expression in the rat spinal cord following selective brachial plexus injury

BACKGROUND： The neuropeptide, substance P, has various bioactivities and is widely distributed in the central nervous system. Substance P participates in neural transmission in the spinal cord and plays an important role in regeneration and repair of nerve injury. OBJECTIVE： To investigate substance P mRNA expression in the anterior horn of the spinal cord following brachial plexus injury. DESIGN, TIME AND SETTING： A molecular cell biology randomized controlled study was performed at the Department of Anatomy, Zhongshan Medical College, Sun Yat-sen University and the DaAn Gene Laboratory in May 2005. MATERIALS： A total of 29 adult male Sprague Dawley rats were randomly assigned to a control group （n = 5） and an injury group （n = 24）. METHODS： The injury group was divided into three subgroups. In subgroup A, the right seventh cervical vertebra （C7） anterior root was avulsed, and the residual nerve root at the distal end was removed. In subgroup B, the right C7 anterior root was avulsed, and the right C5 first thoracic vertebrae （T1） posterior root was incised. Thus afferent pathways of the posterior root that connected with the anterior horn motor neurons were blocked. In subgroup C, the right C7 anterior root was avulsed, and a right C56 hemisection was performed. Thus the descending fiber pathways of the cortex that connected with anterior horn motor neurons were blocked. In the control group, the C5-T1 vertebral plate was opened, and then the skin was sutured. MAIN OUTCOME MEASURE： Substance P mRNA expression in the anterior horn of the spinal cord was quantified using fluorescent quantitative reverse transcription-polymerase chain reaction. RESULTS： Substance P mRNA expression was low in the anterior horn of the rat spinal cord in the control group. Substance P mRNA expression in the anterior horn of the spinal cord was upregulated and was significantly higher in the injury group compared with the control group （P 〈 0.01）. Substance P mRNA expression was highest in subgroup B. CONCLUSION： Brachial plexus anterior root avulsion is responsible for increased substance P expression in the anterior horn of the rat spinal cord. Pathway disjunction in efferent fibers of the posterior root or cortex does not have an effect on substance P expression in the anterior horn of the spinal cord.

STUDIES ON THE RELATIONSHIP BETWEEN SUBSTANCE P AND ABNORMAL GASTROINTESTIANL TRANSIT

Objective To realize the relationship between substance P(SP) and abnormal gastrointestinal transit.Methods By radioimmunoassay, concentration of SP in sigmoid mucosa was determined in 12 healthy volunteers, 15 slow and 10 fast transit patients.Results The concentration was (27.68±15.42)μg/g,(24.07±5.76)μg/g and (28.61±18.34)μg/g,respectively.They had no statistical difference.Conclusion There was no relationship between concentration of SP in sigmoid mucosa and abnormal gastrointestinal transit.

Experimental study on the regulation effect of Qiaoqin Qingfei agent on cough variant asthma based on airway neurogenic inflammation

Objective:To investigate the mechanism of regulation of airway neurogenic inflammation by Qiaoqin Qingfei agent in rats with cough variant asthma(CVA).Methods:48 SD rats were randomly divided into blank group,model group,montelukast sodium group(1.05 mg/kg)and high,medium and low dose groups(26,13,6.5 g/kg),with 8 rats in each group.The rat CVA model was established by the method of ovalbumin(OVA)combined with aluminum hydroxide(Al(OH)3)sensitization and repeated stimulation.From the second day of sensitization,the rat CVA model was given by gavage for 28 days.The pathological changes of lung tissue were observed under microscope by HE staining.The content changes of nerve growth factor(NGF)and substance P(SP)in alveolar lavage fluid(BALF)were determined by double-antibody sandwich ABC-ELISA,and the protein expression levels of NGF and SP in lung tissue were detected by immunohistochemistry.Results:Pathological findings showed significant inflammatory manifestations in the model group,and the inflammatory infiltration in the high-dose,medium-dose and low-dose groups of Qiaoqin Qingfei agent and montelukast sodium groups were alleviated to varying degrees.Compared with blank group,the protein expression levels of NGF and SP in lung tissue of model group were significantly increased(P<0.01).Compared with model group,the protein expression levels of NGF and SP in lung tissue and the contents of NGF and SP in alveolar lavage fluid in high-dose,medium-dose and low-dose groups and montelukast sodium group were significantly decreased(P<0.05).Conclusion:Qiaoqin Qingfei agent may reduce airway inflammation and relieve cough variant asthma by regulating the protein expression levels of NGF and SP in airway neurogenic inflammation.

Rizatriptan benzoate influences the endogenous pain modulatory system in a rat model of migraine

The present study utilized a nitroglycerin-induced rat model of migraine to detect the effects of rizatriptan benzoate on proenkephalin and substance P gene expression in the midbrain using real-time quantitative polymerase chain reaction and investigate whether rizatriptan benzoate can regulate the endogenous pain modulatory system. The results showed that rizatriptan benzoate significantly reduced expression of the mRNAs for proenkephalin and substance P. Rizatriptan benzoate may inhibit the analgesic effect of the endogenous pain modulatory system.

Circadian regulation of Limulus visual functions:A role for octopamine and cAMP

The purpose of this contribution is to review our current understanding of the source and biochemistry of the circadian efferent input to the eyes of the American horseshoe crab Limuluspolyphemus and the impact of this input on the structure, physiology and biochemistry of Limulus eyes. Special emphasis is given to the role of the biogenic amine octopamine and bio- chemical cascades it activates in the eyes. In addition to reviewing published data, we present new data showing that octopamine elevates cAMP levels in Limulus lateral eyes, and we partially characterize the pharmacology of the receptors involved in this response. We also present new data showing that octopamine regulates gene expression in Limulus lateral eyes by activating a cAMP cascade

EFFECT OF ERYTHROMYCIN ON GASTRIC DYSMOTILITY AND NEUROENDOCRINE PEPTIDES IN RATS WITH DIABETES MELLITUS

Objective To investigate the effect of erythromycin on the contractive activity of the isolated gastric antrum smooth muscle and somatostatin （SS）, vasoactive intestinal peptide （VIP）, motilin （MTL）, and substance P （SP） in plasma and isolated gastric antrum tissue of diabetes mellitus （DM） rat models. Methods Thirty male Sprague-Dawley rats were divided into three groups： control group （n = 10）, DM group （n = 10）, and erythromycin group （DM models with erythromycin treatment, n = 10）. A single dose of streptozotocin （100 mg/kg, dissolved in 0. I mol/L citric acid buffer, pH4.5） was injected intraperitoneally. After 48 to 72 hours, rats with blood glucose above 16.7 mmol/L and urine glucose level to be （＋＋＋ ） to （＋＋＋＋） over one week were considered successful DM models. The resting tension, mean contractile amplitude and fi＇equency of spontaneous change in isolated longitudinal and circular gastric antrum smooth muscle strips were measured. SS, VIP, MTL, and SP levels in plasma and gastric antrum tissue were measured using radioimmunoassay. Results （1） In the isolated gastric antrum smooth muscle strips, the gastric motility parameters were lower in DM group than those in control group except circular smooth muscle contractile amplitude and longitudinal smooth muscle contractile fi＇equency. The gastric motility parameters were significantly strengthened in erythromycin group, compared with DM group except longitudinal smooth muscle resting tension （P 〈 0.01 ）. （2） Plasma SS, VIP, and MTL concentrations in DM group were higher than those in control （P 〈 0.05）, while the SP level decreased （P 〈 0.05）. In the gastric antrum, SS of DM group was significantly higher than that of control group （P 〈 0.01 ）, while SP and MTL levels were lower than those of control group （P 〈 0.05 and P 〈 0.01, respectively）. However, the level of VIP in gastric antrum tissue did not change among three groups. The plasma level of SS in erythromycin group was higher than that of DM group （P 〈 0.05）. （3） The blood glucose was lower in erythromycin group than DM group （P 〈 0.01 ）. Conclusions Erythromycin has direct effects on contractive activity of gastric smooth muscle in diabetic rats, but there are few effects on neuroendocrine peptides. Gastric-motility disorders in diabetic rats have a correlation with the changes of neuroendocrine peptide levels in plasma and gastric antrum tissue.