Extracellular vesicles of immune cells; immunomodulatory impacts and therapeutic potentials.

Extracellular vesicles (EVs) are a diverse collection of lipid bilayer-membrane-bound particles which are released from cells into the extracellular space and biologic fluids. In multicellular organisms, these vesicles facilitate the exchange of bioactive compounds such as RNA, DNA, proteins, various metabolites, and lipids between the cells. EVs are produced and released by almost all eukaryotic cells including immune cells and can have immunomodulating effects by either stimulation or suppression of their activities. This immune-modulating feature may provide a promising strategy for treating immune-mediated diseases such as cancer, neurodegenerative diseases, autoimmune disorders and graft-versus-host disease. Moreover, immune cell-derived EVs have received attention as potential biomarkers for being used as diagnostic tools and preventive strategies such as for developing vaccines. In this review, we focus on the EVs produced by different immune cell types, their effects on the immune system, and highlight their potential applications for immunotherapy.

Effect of Trans-Anethole on Gene Expression of Steroidogenic Enzymes in the Ovary of Polycystic Ovary Syndrome Model Rate:.

BACKGROUND: The process of steroidogenesis is crucial to the normal function of the ovaries. In individuals with polycystic ovary syndrome (PCOS), the activity of related enzymes in this process is disrupted. In the present study, the effect of trans-anethole was investigated on gene expression of steroidogenesis enzymes in PCOS model rats. MATERIALS AND METHODS: In this experimental study, thirty female rats were divided into six groups (n=5 per group). Fifteen PCOS rats in three groups received intraperitoneal injections of distilled water, 50, and 80 mg/kg of trans-anethole, respectively. Also, 15 intact rats in three groups received intraperitoneal injections of distilled water, 50, and 80 mg/kg trans-anethole. The expression of steroidogenesis genes was determined using real-time reverse transcription polymerase chain reaction. RESULTS: The mRNA level of Cyp19 significantly increased in intact rats receiving 80 mg/kg trans-anethole compared to the control group. The Cyp19 level in PCOS groups was significantly reduced compared to the control group. The mRNA level of Cyp19 in PCOS groups that resived 50 or 80 mg/kg trans-anethole increased compared to PCOS rats, but this increase was not statistically significant. The mRNA level of Cyp17 did not significantly change in intact and PCOS rats that received trans-anethole compared to the control group. CONCLUSION: Trans-anethole may improve PCOS complications due to its involvement in regulating steroidogenesis.

Novel Gold Nanoparticles: Green Synthesis with Eryngium thyrsoideum Boiss Extract, Characterization, and In Vivo Investigations on Inflammatory Gene Expression and Biochemical Parameters in Type 2 Diabetic Rats.

In this work, we synthesized and reported gold nanoparticles (Au NPs) with Eryngium thyrsoideum Boiss plant extract for first time. The plant extract has important effect as reducing and stabilizing agent for preparation of Au nanoparticles. The synthesized gold nanoparticles were characterized with FT-IR, UV-vis, XRD, SEM, and TEM analyses. All analyses confirmed successful synthesis of gold nanoparticles with high purity. The antidiabetic activity of synthesized Au NPs was investigated on type 2 diabetic rats by studying their influences on serum biochemical parameters and inflammatory markers. Obtained results revealed that hepatic enzymes, TNF-α, and interleukin-6 of diabetic rats receiving gold nanoparticles decreased in compare with healthy control rats. As inflammatory markers are main reasons for hyperglycemic-induced insulin resistance in diabetes, Au NPs have a possible option for management of the diabetes-related complication via their potent anti-inflammatory and hypoglycemic effects.

Thyroxine Accelerates Functional Recovery in a Rat Model of Sciatic Nerve Crush.

AIM: To see how thyroxine affects the sensory and motor function of a damaged sciatic nerve in male rats. MATERIAL AND METHODS: Forty adult male Wistar rats were allocated to four groups, 10 individuals each. Then, crush injury was done on the right sciatic nerve in all the groups using a vessel clamp. In thyroxine-treated groups and after the crush, the rats were given regular doses of thyroxine (5 and 10 ?g/kg) for one week intraperitoneally. Negative control group was treated intraperitoneally with distilled water as a vehicle. In sham operated group, only surgical procedures were performed without nerve crush. Then, behavioral, histological, and morphometric parameters were assessed at the regeneration time. RESULTS: After one week of treatment with thyroxine, the motor function improved significantly following a sciatic nerve crush (P ? 0.05). Also, morphometric parameters and sensory restoration improved in thyroxine-treated groups. CONCLUSION: Findings of this study showed that neuro-protective effects of thyroxine can be due to the stimulatory effects of thyroxine in myelin sheath formation and increasing the expression of SCG10 protein which is required for the development of growth cones.

Biosynthesis of Novel Silver Nanoparticles Using Eryngium thyrsoideum Boiss Extract and Comparison of their Antidiabetic Activity with Chemical Synthesized Silver Nanoparticles in Diabetic Rats.

In the present study, silver nanoparticles (1) were synthesized by green method using Eryngium campestre Boiss aqueous extract and silver nanoparticles (2) were synthesized with chemical method. The silver nanoparticles (1) and (2) were characterized with FT-IR, UV-Vis, XRD, EDX, SEM, and TEM analyses. The effects of silver nanoparticles (1) and (2) were investigated on glucose, hematology, and blood biochemical parameters in alloxan- induced diabetes type 1 model rats. Diabetic or intact rats received intraperitoneal injection of saline or 2.5 mg/kg of silver nanoparticles (1) and (2) for 14 consecutive days. Hematological parameters and serum concentration of FBS, HbA1C, ALT, AST, GGT, ALP, albumin, creatinine, and urea were determined. Interestingly, silver NPs (1) or (2) did not exert toxic influences on hematological parameters and liver and kidney function in intact rats. Both silver nanoparticles (1) and (2) exert hypoglycemic effects in diabetic rats. They did not alter urea, creatinine, and hematological parameters except white blood cell (WBC) count in diabetic rats. Silver nanoparticles (1) decreased significantly liver enzyme levels including ALT and AST of diabetic rats. However silver nanoparticles (2) could not suppress the increased levels of liver enzymes in diabetic rats. In comparison with silver nanoparticles (2), the silver nanoparticles (1) are more protective than the same dose of silver nanoparticles (2) in the regulation and improving the liver function in diabetic rats. Also, silver nanoparticles (1) may exert protective effects on liver damage of diabetic rats rather than kidney damage.

Cerium oxide nanoparticles as a new neuroprotective agent to promote functional recovery in a rat model of sciatic nerve crush injury.

BACKGROUND: Peripheral nerve injury is a common clinical disorder. The aim of the present study was to investigate the role of cerium oxide nanoparticles on axonal regeneration and functional recovery of the sciatic nerve after a crush injury in the rat model. METHOD: A total of 40 adult male Wistar rats were divided into four groups. The animals underwent deep anesthesia. Afterward, the right sciatic nerve of rats was exposed and crushed. In two experimental groups, rats were treated intraperitoneally with cerium oxide nanoparticles at the dosage of 20 or 80 mg/kg daily for 1 week. The control group was given a vehicle. Then, during the nerve regeneration motor and sensory function recovery tests, histomorphometric evaluations, histological assessment of gastrocnemius muscle, and gastrocnemius muscle wet weights tests were performed. RESULTS: Results demonstrated that the rate of nerve regeneration increased with the administration of cerium oxide nanoparticle in high doses. Also, the morphometric analysis showed that the number of myelinated fibers and myelin sheath thicknesses was significantly greater in the cerium oxide nanoparticle group versus the control group. Other parameters also improved in the cerium oxide nanoparticle treatment groups compared with the control group. CONCLUSION: These data indicate that this nanoparticle has therapeutic potential and can be considered as a new treatment for nervous system regeneration.

Co-regulative effects of chitosan-fennel seed extract system on the hormonal and biochemical factors involved in the polycystic ovarian syndrome.

There is a renewed interest in the application of chitosan-based drug delivery systems over the last few years. In this study, the ionic gelation method was used to prepare chitosan-engaged tripolyphosphate ions, as the cross-linking molecule, (Chit-TPP) and concurrent loading of the biomolecules of the ethanolic extract of fennel, Foeniculum vulgare, seed (FEC@NBC). The samples were characterized by SEM, DLS, TGA, FTIR, XRD, GC-MS, and zeta potential, and their effects on the related hormonal and biochemical factors of the rats with polycystic ovarian syndrome (PCOS) were assessed. The estradiol valerate-induced PCOS in female rats was confirmed by vaginal smear test and subsequent histological screening. The PCOS-induced rats were treated by fennel seed extract (FSX), Chit-TPP, and FEC@NBC. The process of treatment was monitored by measuring the serum levels of testosterone, luteinizing hormone, follicle-stimulating hormone, insulin, glucose, high-density lipoprotein cholesterol, total cholesterol, and total triglyceride after 16 days of treatment and compared with healthy control and untreated PCOS-control groups. The FEC@NBC administration contributed to the remarkable hormonal, glucose, and lipid profile regulation in the rats with PCOS. The significance of FEC@NBC performance in dealing with PCOS complications compared to that of the only extract could be resulted from the effective targeted delivery and stability of phytomolecules when encapsulated in Chit-TPP.

Influences of Serotonin Hydrochloride on Adiponectin, Ghrelin and KiSS1 Genes Expression.

BACKGROUND: Serotonin and kisspeptin stimulates gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) release while ghrelin and adiponectin inhibit them. In the present experimental study, the effects of central injection of serotonin were investigated on LH concentration, KiSS1, adiponectin, and ghrelin genes expression. MATERIALS AND METHODS: Fifteen Wistar male rats in three groups received saline or serotonin hydrochloride via the third cerebral ventricle. Blood samples were collected via the tail vein. Serum LH concentration and relative gene expression were evaluated by radioimmunoassay and real-time polymerase chain reaction method, respectively. RESULTS: Serotonin significantly increased the mean serum LH concentration and KiSS1 gene expression levels compared to the saline group. Serotonin significantly decreased the mean ghrelin and adiponectin genes expression levels compared to the saline group. CONCLUSION: The serotonergic pathway may have stimulatory effects on hypothalamic kisspeptin synthesis, partly via inhibiting hypothalamic ghrelin and adiponectin neural activity.

The effects of supraphysiological levels of testosterone on neural networks upstream of gonadotropin-releasing hormone neurons.

OBJECTIVES: Several pathological conditions are associated with hyper-production of testosterone; however, its impacts are not well understood. Hence, we evaluated the effects of supraphysiological levels of testosterone on gonadotropin-releasing hormone (GnRH) system in the hypothalamus of male rats. Also, we assessed the expression of two excitatory (kisspeptin and neurokinin-B) and two inhibitory (dynorphin and RFamide-related-peptide) neuropeptides upstream of GnRH neurons as possible routes to relay androgen information. MATERIALS AND METHODS: Gonadectomized (GDX) male rats received single injection of 100, 250 or 500 mg/kg testosterone undecanoate and three weeks later, posterior (PH) and anterior (AH) hypothalamus was dissected for evaluation of target genes using quantitative RT-PCR. RESULTS: We found that GnRH mRNA in the PH was high in GDX rats and 500 mg/kg testosterone reduced GnRH level expression. Finding revealed extremely high level of Kiss1 mRNA in the PH of GDX rats. However, in GDX rats treated with different levels of testosterone, Kiss1 expression was not significantly different than control. We also found that testosterone replacement increased the Kiss1 mRNA level in the AH. Moreover, neurokinin-B mRNA level in PH of GDX rats was similar to control. However, excess testosterone levels were effective in significantly inducing the down-regulation of neurokinin-B expression. The basal level of dynorphin mRNA was increased following testosterone treatments in the AH, where we found no significant difference in the level of RFamide-related-peptide mRNA between the experimental groups. CONCLUSION: Excess levels of testosterone could act differently from its physiological concentration to regulate hypothalamic androgen sensitive neurons to control GnRH cell.

Morphine and kisspeptin influences on 5-α reductase and aromatase gene expression in adult male rats.

OBJECTIVES: Kisspeptin and opioids are important factors for controlling GnRH/LH secretion. In present study, influences of kisspeptin or morphine were investigated on 5α- reductase or aromatase (CYP19) genes expression in the hypothalamus, testis and liver. It aimed to investigate whether kisspeptin pathway may control morphine effects on plasma concentration of testosterone. MATERIALS AND METHODS: Twenty adult male rats in four groups received saline/saline, kisspeptin (1 nmol)/saline, morphine (5 mg/kg)/saline or kisspeptin/morphine respectively. Mean relative 5α-reductase and aromatase mRNA levels were determined by RT-PCR. RESULTS: Morphine/saline injection increased significantly mean relative mRNA levels of hypothalamic 5α-reductase or aromatase compared to saline/saline. While morphine/saline did not alter mRNA levels of them compared to saline/saline group in the testis and liver. Kisspeptin/saline did not significantly decrease mean relative 5α-reductase or aromatase genes expression compared to saline/saline group in the hypothalamus, testis and liver. Injections of kisspeptin/morphine did not significantly decrease mean relative 5α-reductase or aromatase genes expression compared to morphine/saline group. CONCLUSION: Up-regulation of hypothalamic 5α-reductase or aromatase mRNA levels may partly induce the inhibitory effects of morphine on GnRH/LH release. Different effects of morphine on aromatase or 5α- reductase genes expression levels in the liver and testis compared to brain may be partly due to different sensitivity or functions of them to morphine used dose.

Hypothalamic KiSS1/GPR54 Gene Expressions and Luteinizing Hormone Plasma Secretion in Morphine Treated Male Rats.

BACHGROUND: The inhibitory effects of morphine and the stimulatory influence of kisspeptin signaling have been demonstrated on gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) release. Hypothalamic kisspeptin is involved in relaying the environmental and metabolic information to reproductive axis. In the present study, the role of kisspeptin/ GPR54 signaling system was investigated on relaying the inhibitory influences of morphine on LH hormone secretion. MATERIALS AND METHODS: In this experimental study, 55 wistar male rats weighing 230-250 g were sub-grouped in 11 groups (in each group n=5) receiving saline, kisspeptin (1 nmol), peptide234 (P234, 1 nmol), morphine (5 mg/kg), naloxone (2 mg/kg), kisspeptin/P234, morphine/naloxone, kisspeptin/morphine, kisspeptin/naloxone, P234/morphine or P234/naloxone respectively. Blood samples were collected via tail vein. Mean plasma (LH) concentrations and mean relative KiSS1 or GPR54 mRNA levels were determined by radioimmunoassay (RIA) and real time reverse transcriptase-polymerase chain reaction (RT-PCR), respectivwely. RESULTS: Morphine significantly decreased mean plasma LH concentration and mean relative KiSS1 gene expression compared to saline; while it did not significantly decrease mean relative GPR54 gene expression compared to saline. Naloxone significant increased mean LH level and mean relative KiSS1 gene expression compared to saline; while it did not significantly increase mean relative GPR54 gene expression compared to saline. Injections of kisspeptin plus morphine significantly increased mean LH concentration compared to saline or morphine, while simultaneous infusions of them significantly declined mean plasma LH level compared to kisspeptin. In kisspeptin/naloxone group mean plasma LH level was significantly increased compared to saline or naloxone. Co-administration of P234/morphine significantly decreased mean LH concentration compared to saline. CONCLUSION: Down regulation of KiSS1 gene expression may be partly involved in the mediating the inhibitory effects of morphine on reproductive axis.

Oxytocin Intranasal Administration Affects Neural Networks Upstream of GNRH Neurons.

The last decade has witnessed a surge in studies on the clinical applications of intranasal oxytocin as a method of enhancing social interaction. However, the molecular and cellular mechanisms underlying its function are not completely understood. Since oxytocin is involved in the regulation of hypothalamic-pituitary-gonadal axis by affecting the gonadotropin-releasing hormone (GNRH) system, the present study addressed whether intranasal application of oxytocin has a role in affecting GNRH expression in the male rat hypothalamus. In addition, we assessed expression of two excitatory (kisspeptin and neurokinin B) and two inhibitory (dynorphin and RFamide-related peptide-3) neuropeptides upstream of GNRH neurons as a possible route to relay oxytocin information. Here, adult male rats received 20, 40, or 80 µg oxytocin intranasally once a day for 10 consecutive days, and then, the posterior (PH) and anterior hypothalamus (AH) dissected for evaluation of target genes. Using qRT-PCR, we found that oxytocin treatment increased Gnrh mRNA levels in both the PH and AH. In addition, oxytocin at its highest dose increased kisspeptin expression in the AH by around 400%, whereas treatments, dose dependently decreased kisspeptin mRNA in the PH. The expression of neurokinin B was increased from the basal levels following the intervention. Furthermore, although intranasal-applied oxytocin decreased hypothalamic RFamide-related peptide-3 mRNA level, the dynorphin mRNA was not affected. These observations are consistent with the hypothesis that applications of intranasal oxytocin can affect the GNRH system.

Orexin Decreases Aromatase Gene Expression in The Hypothalamus of Androgenized Female Rats.

BACKGROUND: Orexin is a hypothalamic orexigenic neuropeptide, which third cerebral injection of it mainly exerts inhibitory effects on reproductive functions. It increases significantly the Aromatase (Cyp19) gene expression in the hypothalamus of male rats. Aromatase is an enzyme which converts androgens to estradiol in the hypothalamus of rats. Prenatal or neonatal exposure of females to testosterone masculinizes the pattern of Cyp19 mRNA levels in adulthood. In the present study the effects of central injections of orexin-A on hypothalamic Cyp19 gene expression of adult female rats were investigated, while they had been androgenized on third day of postnatal life. MATERIALS AND METHODS: In this experimental study, twenty female Wistar rats received subcutaneous injections of testosterone propionate (50 µg/100 µl) on their third day of postnatal life. Adult androgenized rats weighing 180-220 g, received either 3 µl saline or one of 2, 4 or 8 µg/3 µl concentration of orexin via third cerebral ventricle. Five non-androgenized rats, as control group, received intra cerebral ventricle (ICV) injection of 3 µl saline. The hypothalamuses were dissected out and mean Cyp19 mRNA levels were determined by semi-quantitative real time-polymerase chain reaction (PCR) method. Data were analyzed by unpaired t test and one-way ANOVA using SPSS software, version 16. RESULTS: Mean relative Cyp19 mRNA level was significantly increased in the hypothalamus of androgenized compared to non-androgenized female rats. Central injec- tions of 2, 4 or 8 µg/3 µl orexin decreased significantly the hypothalamic Cyp19 mRNA level of androgenized rats compared to androgenized-control groups. CONCLUSION: The results suggested that the orexin may exert inhibitory effects on the gene expression of Cyp19 in the hypothalamus of neonatal androgenized female rats in adulthood.

The immunomodulatory activity of secondary metabolites isolated from Streptomyces calvus on human peripheral blood mononuclear cells.

BACKGROUND: The natural products derived from micro-organisms are potential candidates for the discovery of novel drugs. Streptomyces bacteria are prolific sources of secondary metabolites with a wide variety of biological activities. Streptomyces calvus (S. calvus) is one strain of this genus and may be an appropriate candidate for isolating new compounds. In this study, the immunomodulatory effects of S. calvus secondary metabolites on the expression of various cytokine genes by human peripheral blood mononuclear cells (PBMCs) were evaluated. METHODS: A bacterial sample was inoculated in Mueller Hinton Broth and secondary metabolites were extracted. PBMCs were isolated from venous blood and were treated with S. calvus secondary metabolites for 48 h. The cell proliferation was assessed by Methyl tetrazolium bromide (MTT) assay and quantitative real-time polymerase chain reaction (qRT-PCR) assays to survey mRNA expressions of selected pro-inflammatory and inhibitory cytokine genes. RESULTS: Secondary metabolites augmented interleukin-2 and interferon-γ gene expression in PBMCs at low doses and also reduced the levels of immunosuppressive cytokine interleukin-10. In addition, the proliferation of PBMCs substantially increased in response to metabolite treatment in a concentration-dependent manner (p < 0.001). CONCLUSION: This in vitro study revealed that the secondary metabolites from S. calvus can successfully stimulate human PBMCs. Therefore, these metabolites have the potential to serve as robust immunomodulators.

Morphine attenuates testosterone response to central injection of kisspeptin in male rats.

BACKGROUND: Kisspeptin and naloxone stimulate the reproductive axis while morphine inhibits its function. We have investigated the effect of central injection of kisspeptin-10 on mean plasma testosterone concentration in morphine or naloxone pretreated rats. MATERIALS AND METHODS: In this experimental study, 60 male Wistar rats that were divid- ed into 12 groups (n=5 per group) received saline, kisspeptin (1 nmol, ICV), naloxone (2 mg/kg, subcutaneously), morphine (5 or 10 mg/kg, sc) or co-administrations of kisspeptin, morphine and naloxone at 09:00 - 09:30. In the co-administrated groups, kisspeptin was injected 15 minutes following morphine or naloxone injections. Blood samples were collected 60 minutes following injections via the tail vein. Plasma testosterone concentration was measured by a rat testosterone ELISA kit. RESULTS: Central injection of kisspeptin or subcutaneous injection of naloxone significantly increased the mean plasma testosterone concentration compared to saline while subcutaneous injections of different doses of morphine (5 or 10 mg/kg) significantly decreased testosterone compared to saline. The results revealed that morphine significantly attenuated the testosterone increase after kisspeptin injection compared to kisspeptin while a stimulatory additive effect was observed in the kisspeptin/naloxone group compared to either naloxone or kisspeptin. CONCLUSION: Morphine and kisspeptin systems may interact with each other to control the hypothalamic-pituitary-gonadal (HPG) axis.

Interactions of morphine and Peptide 234 on mean plasma testosterone concentration.

BACKGROUND: Kisspeptin-GPR54 system stimulates the hypothalamus-pituitary-gonadal (HPG) axis; dysfunction of the gene encoding the GPR54 receptor causes hypogonadism and infertility. Opioid peptides inhibit the reproductive axis. Peptide 234 is a GPR54 receptor antagonist and blocks the stimulatory effects of kisspeptin on HPG axis. OBJECTIVES: Interactions of morphine, kisspeptin and peptide 234 on mean plasma testosterone concentration was investigated in rats. . MATERIALS AND METHODS: In the present experimental study, seventy male Wistar rats in 14 groups (n = 5 in each group) received saline, different doses of kisspeptin (100 pmol, 1 or 3 nmol, Intracerebroventricular (ICV)), P234 (1 or 2.5 nmol) or Co- administration of kisspeptin, P234, morphine and naloxone at 09:00 - 09:30 am. In the co-administrated groups, kisspeptin was injected at 15 min following P234, morphine or naloxone injections. Blood samples were collected 60 min following injections. Plasma testosterone concentration was measured using the rat testosterone ELISA kit. RESULTS: Injections of kisspeptin (1 or 3 nmol) significantly increased the mean testosterone concentration compared to saline. Injection of different doses of P234 (1 or 2.5nmol) did not significantly decrease mean testosterone compared to saline. Co-administration of kisspeptin and different doses of P234 significantly decreased mean testosterone concentration compared to the kisspeptin group. Co-administration of P234/morphine or P234/naloxone significantly decreased mean testosterone concentration compared to kisspeptin/saline, kisspeptin/morphine or kisspeptin/ naloxone groups. CONCLUSIONS: Morphine and kisspeptin/GPR54 signaling pathway may interact with each other to control the hypothalamic-pituitary-gonadal axis.

Effects of intrahippocampal injection of ghrelin on spatial memory in PTZ-induced seizures in male rats.

Ghrelin (gh) is a peptide hormone that may affect learning and memory. There is some evidence that ghrelin can have antiepileptic effects. So we decided to investigate the possible effects of ghrelin on spatial memory following PTZ-induced seizures in male rats. Ninety male rats were divided into 9 groups including control, saline, ghrelin (0.3, 1.5 or 3 nmol) and pentylenetetrazol (PTZ, 50 mg/kg, i.p.) plus saline or ghrelin (0.3, 1.5 or 3 nmol). All groups were trained in Morris water maze (MWM) for two consecutive days. Our results showed that ghrelin significantly improves spatial memory at the doses of 1.5 or 3 nmol (P<0.05) in normal rats. We also demonstrated the significant impairment of spatial memory in PTZ group (P<0.05). Intrahippocampal injection of ghrelin at the dose of 3 nmol significantly improved spatial memory in PTZ+gh group compared to PTZ group (P<0.05). These findings suggest that ghrelin as a neuropeptide can improve spatial memory in PTZ-treated rats.

The effect of central injection of ghrelin and bombesin on mean plasma thyroid hormones concentration.

Ghrelin increases food intakes and body weight. Bombesin decreases food intakes and inhibits the stimulatory effect of Ghrelin on food intakes. Thyroid hormones have a crucial role in the regulation of body weight and yet the effect of bombesin on thyroid axis activity is not fully clear. Therefore, the goal of this study was to determine the effect of different doses of Ghrelin or bombesin on mean plasma thyroid-stimulating hormone (TSH), Triiodothyronine (T3) and Thyroxin (T4) concentration and also, the effect of interaction between Ghrelin and bombesin on thyroid axis activity. Forty-nine rats in seven groups received saline or different doses of Ghrelin (4, 10 or 15 nmol) and bombesin ( 2.5, 5 or 10 nmol) and forty-two rats in six groups received simultaneous injection of Ghrelin (10 or 15 nmol) and different doses of bombesin (2.5, 5 or 10 nmol) via lateral cerebral ventricle. Blood samples were collected via decapitation 20 min after the injection and plasma was assayed for plasma TSH, T3 and T4 concentration by Radioimmunoassay (RIA). Ghrelin significantly decreased the concentration of mean plasma thyroid hormones compared to saline. Bombesin did not significantly increase thyroid hormones concentration compared to saline but bombesin blocked the inhibitory effect of Ghrelin on thyroid axis activity. Bombesin may be the antagonist of Ghrelin action.