Treadmill Exercise Improves Behavioral and Neurobiological Alterations in Restraint-Stressed Rats.

Stress is a state that is known to impact an organism's physiological and psychological balance as well as the morphology and functionality of certain brain areas. In the present work, chronic restraint stress (CRS) model rats treated with treadmill exercise were used to examine anomalies associated to emotion and mood as well as molecular changes in the brain. Forty male Sprague-Dawley rats were divided into control, stress, exercise, and stress+exercise groups. CRS were exposed to stress group rats and exercise group underwent a chronic treadmill exercise. Depressive-like behavior was evaluated with the forced swim test (FST) and tail suspension test (TST). For assessing anxiety-like behavior, the light-dark test (LDT) and the open field test (OFT) were used. The Morris water maze test (MWMT) was used for testing memory and learning. Brain's monoamine level and the expression of genes related to stress were measured. It was discovered that CRS lengthens latency in the MWMT, increases immobility in the FST and TST, decreases time in the light compartment, and causes hypoactivity in the OFT. CRS reduced the dopamine levels in the nucleus accumbens(NAc). Brain-derived neurotrophic factor (BDNF), dopamine receptors, and serotonin receptor (HTR2A) gene expression in the prefrontal cortex, corpus striatum, and hypothalamus were decreased by CRS. Exercise on a treadmill leads to increase NAc's dopamine and noradrenaline levels and prevented behavioral alterations. Exercise increased the alterations of BDNF expressions in the brain in addition to improving behavior. As a result, CRS-induced behavioral impairments were effectively reversed by chronic treadmill exercise with molecular alterations in the brain.

TRPM2 may be involved in high fructose corn syrup-induced anxiety-like behavior in adult male rats.

Excessive high fructose corn syrup (HFCS) consumption is known to cause oxidative stress, which induces transient receptor potential melastatin type 2 (TRPM2) channel gating. Oxidative stress-induced TRPM2 gating is suggested to play an important role in neurons, indicating a role for the TRPM2 channel in a variety of neuropsychiatric disorders including depression and anxiety. We investigated the effects of HFCS and chronic immobilization stress (CIS) on TRPM2 channel immunoreactivity, anxiety, and depressive-like behaviors in adult male rats. The male rats (n=8/group) were divided into 4 groups: Control, 20% HFCS (F20), 40% HFCS (F40), and stress. The control group received tap water, and F20 and F40 groups were exposed to HFCS 20% and 40% respectively for 14 consecutive days. Rats in the stress group were subjected to immobilization stress for 3 or 6 hours daily in the first and second weeks to induce CIS. Then, light/dark tests, open field tests (OFT), and tail suspension tests (TST) were performed, respectively. In the light/dark test, the time spent in the dark chamber significantly increased in all groups vs the control group (P<0.01). In support of this result, time spent in the light chamber significantly decreased in all groups vs the control group (P<0.01). Besides, CIS significantly increased depressive-like behavior in the stress group vs the control group (P<0.05). In serum hormone levels, corticosterone (CORT) levels significantly increased in the F40 and stress groups vs the control group (P<0.01). TRPM2 immunoreactivity significantly increased in the hippocampus, prefrontal cortex (PFC), nucleus accumbens (NaC), and amygdala regions by HFCS and CIS treatments. For the first time in the present study,  showed that f increased immunoreactivity of the TRPM2 cation channels may be linked to the anxiety-like behavior induced by HFCS.

Treadmill exercise has healing effects on obesity-induced sexual behavior disorder through kisspeptin and kiss1R expression in male rats.

The basic objective of this study was to examine the possible effects of treadmill exercise on obesity-related sexual behavior disorder in obese male rats and the role of kisspeptin in this effect. The rats were separated from their mothers at the age of 3 weeks, and classified into four groups as Control (C): normal diet-sedentary group, Exercise (E): normal diet-exercise group, Obese (O): high-fat diet-sedentary group, Obese + Exercise (O+E): high-fat diet-exercise grouSexual behavioral testing was conducted in the rats. At the end of the study, brain samples were taken from the animals for gene expression analyses. The treadmill exercise caused a significant increase in the O+E Group compared to the O Group in kisspeptin and kiss1R gene expression and in EF, ML, IL, MF, IF, III, EL, PEI, IR1, MFT, IFT, IRT sexual behavior parameters (p<0.05), and a significant decrease in ML, IL, III, EL sexual behavior parameters (p<0.05). Treadmill exercise caused a significant decrease in EF, ML, IL, MF, IF, III, EL, PEI, IR1, MFT, IFT, IRT sexual behavior parameters and kisspeptin and kiss1R gene expression in the hypothalamus, hippocampus, prefrontal cortex and corpus striatum in E Group compared to C Group (p<0.05), and a significant increase in ML, IL, III, EL sexual behavior parameters (p<0.05). Based on this effect, we believe that it is caused by an increase in kisspeptin and kiss1R expression in the hypothalamus, hippocampus, prefrontal cortex and corpus striatum. In conclusion, treadmill exercise-induced kisspeptin secretion may increase GnRH secretion and cause hypothalamo-pituitary gonadal axis activation and ameliorative effect on deteriorated sexual function.

The Effects of Chronic Asprosin Administration on Sense of Smell and Sexual Behavior in Female Rats.

INTRODUCTION: Asprosin is an adipokine released from white adipose tissue during fasting and acts through the olfactory receptor. It is known that adipokines play roles in reproductive physiology in mammals. However, there are very few studies conducted on role of asprosin in reproductive functions. There are no studies on its relationship with sexual motivation. It was shown in the literature that administration of asprosin to male mice improves olfaction. It is also known that there is a strong correlation between smell and sexual desire. In view of this, it was hypothesized that chronic administration of asprosin would improve olfactory performance and increase sexual incentive motivation in female rats for male partners. METHODS: This hypothesis was tested by applying the hidden cookie test, sexual incentive test, active research test, and sexual behavior test. The changes in serum hormone levels in female rats that chronically received asprosin were also measured and compared. RESULTS: Chronic asprosin exposure increased olfactory performance, male preference ratio, male investigation preference ratio, activity index, and anogenital investigation behavior. Also, serum oxytocin and estradiol levels increased following chronic administration of asprosin in female rats. CONCLUSION: These data suggest that chronic administration of asprosin can result in increased sexual incentive motivation for opposite sex in female rats over increased olfactory performance and changes in reproductive hormones.

Percentages of serum, liver and adipose tissue fatty acids and body weight are affected in female rats by long-term Central kisspeptin treatments.

This study was conducted to determine the possible effects of long-term exogenous kisspeptin and its antagonist P234 on serum, liver and adipose tissue fatty acids (FA) profiles, as well as body weight, in female rats. Kisspeptin (50 pmol) and P234 (1 nmol) were administrated to the weaned Sprague-Dawley female rats by an intracerebroventricular injection from the 26th postnatal day to the 60th postnatal day. Percentages of the serum total saturated FA (∑SFA) and total monounsaturated FA (∑MUFA) were lower in the kisspeptin group. In the adipose tissue, ∑SFA was lower and total unsaturated FA higher in the P234 group. Moreover, long-term central kisspeptin injection caused a decrease in the body weight. When compared to the kisspeptin group, the final body weights were higher in the P234 and kisspeptin + P234 groups. According to our results, we suggest that kisspeptin has a regulatory role in FA metabolism and regulation of body weight.

Asprosin, a novel glucogenic adipokine: a potential therapeutic implication in diabetes mellitus.

OBJECTIVES: We aimed to investigate the effects of asprosin on diabetes with a focus on serum glucose, irisin, ghrelin, leptin levels and hepatic levels of triglycerides (TG), cholesterol, low-density lipoprotein (LDL). METHODS: Asprosin (10 µg/kg) was administered intraperitoneally four times at 3-day intervals and then blood and hepatic parameters above mentioned were investigated in control and diabetic mice. RESULTS: The administration of asprosin increased blood glucose level in healthy animals (p = .05) whereas it did not change blood glucose level in diabetic animals. In addition, while asprosin decreased irisin level and increased ghrelin level, it did not change leptin level in diabetic mice. Therewithal, asprosin decreased the increasing levels in hepatic TG, cholesterol, and LDL in diabetic mice. CONCLUSIONS: Our novel findings implicate that asprosin may be a target molecule in preventing the development and complications of diabetes.

Treadmill exercise training improves the high-fat diet-induced behavioral changes in the male rats.

The purpose of this study was to investigate the effects of treadmill exercise training on obesity-induced behavioral changes in high-fat diet (HFD)-induced male rats. In this study, 40 male Sprague-Dawley rats were divided into 4 groups after they were weaned: Control (C), Exercise (E), Obese (O) and Obese + Exercise (O + E). For the obesity model % 60 high-fat diet were applied. After obesity was induced, rats were either moderate aerobic exercise (treadmill running) trained or left untrained. Different tasks to assess spatial learning and memory (Morris water maze test (MWMT)), depressive-like behavior (forced swimming test(FST), tail suspension test (TST) and anxiety-like behavior (light-dark test (LDT) and open field test (OFT)) were conducted. Exercise caused a significant reduction in duration of immobility in the O group in FST and the decrease in immobility in the O + E rats in TST. The O + E rats demonstrated a significant increase in the time spent in the light box as compared to the O group in the LDT. The O + E rats did not show any behavioral alterations as compared to all the other groups in the OFT. In the O + E group, there was a significant increase in the time spent in the target quadrant compared to the O group in the MWMT. Our results support that treadmill exercise could improve cognitive, depressive-like, anxiety-like behavioral changes in the HFD-induced obese rats.

Irisin Improves High-Fat Diet-Induced Sexual Dysfunction in Obese Male Rats.

INTRODUCTION: Obesity is known to cause sexual dysfunction including erectile dysfunction and poor semen quality. Lifestyle modifications such as exercise have increasingly been more recognized to lower the likelihood of having sexual dysfunction or infertility in obese men. In this context, as an exercise-mimetic hormone, irisin has a potential to improve obesity-related reproductive dysfunctions. We aimed to elucidate possible effects of irisin on high-fat diet (HFD)-induced reproductive dysfunction in obese male rats. METHODS: Rats were divided into four groups: vehicle, irisin, obese, and obese + irisin. The rats in obese and obese+irisin groups were fed with HFD (60% kcal fat) pellets for 12 weeks to induce obesity, and then obesity-induced sexual dysfunction was confirmed by the sexual behavior test (SBT). Irisin and obese+irisin groups received irisin (100 ng/kg/day) infusion by an s.c. osmotic minipump for 4 weeks after HFD-induced obesity was formed. RESULTS: Irisin did improve a number of measures of copulation, including penile erection, ejaculation, and sexual performance, and also improved sperm morphology and motility and decreased fat-induced testicular damage. It decreased serum leptin levels. On the other hand, irisin did not affect serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone. It also increased gene expression of tyrosine hydroxylase (TH) and adrenoceptor alpha 1A (ADRA1A) in the medial preoptic area (mPOA) and nucleus accumbens (NAc). CONCLUSION: Irisin provided a marked enhancement of HFD-induced decrease in libido, potency, sexual performance, and erection in SBT. Taken together, our results emphasize that irisin has a restorative and improver role in HFD-induced reproductive dysfunctions in obese male rats.

Agomelatine, A Potential Multi-Target Treatment Alternative for Insomnia, Depression, and Osteoporosis in Postmenopausal Women: A Hypothetical Model.

Insomnia, which is associated with menopausal depression, is a common symptom of menopause. Both symptoms have a common etiology, and can affect each other significantly. Pharmacological interventions, including hypnotics and antidepressants, and non-pharmacological therapies are generally administered in clinical practice for insomnia treatment. As another menopausal disorder, osteoporosis is described as a disease of low bone mineral density (BMD), affecting nearly 200 million women worldwide. Postmenopausal osteoporosis is common among middle-aged women. Since postmenopausal osteoporosis mainly results from low estrogen levels, menopausal hormone therapy (HT) is considered the first-line option for the prevention of osteoporosis during the menopausal period. However, almost no study has evaluated novel treatments for the combined prevention of insomnia, depression, and osteoporosis. Hence, it is necessary to develop new multi-target strategies for the treatment of these disorders to improve the quality of life during this vulnerable period. Melatonin is the major regulator of sleep, and it has been suggested to be safe and effective for bone loss therapy by MT-2 receptor activity. As a result, we hypothesize that agomelatine, an MT-1 and MT-2 receptor agonist and 5-HT2C receptor antagonist, holds promise in the combined treatment of insomnia, depression, and osteoporosis in middle-aged women during menopause.

Kisspeptin leads to calcium signaling in cultured rat dorsal root ganglion neurons.

Although kisspeptin and GPR54 have been reported to be expressed in the neurons of the dorsal root ganglion (DRG) of rats, and kisspeptin has been suggested to be involved in pain modulation in rodents, there is no study on the effects and mechanisms of kisspeptin on sensory neurons. Therefore, the aim of this study was to investigate the effects and mechanism of kisspeptin on intracellular free calcium levels in cultured rat DRG neurons. Bath application of kisspeptin-10 increased intracellular free calcium levels ([Ca2+]i). In the absence of extracellular calcium, the kisspeptin induced an attenuated but still significant increase in [Ca2+]i. [Ca2+]i responses persisted in the presence of protein kinase C (PKC) inhibitor. Data from this study revealed that kisspeptin-10 activates [Ca2+]i signaling independent of PKC in cultured rat sensory neurons suggesting that peripheral site is also involved in the pain modulating effect of kisspeptin.

Interference of gadolinium dechelated from MR contrast agents by calcium signaling in neuronal cells of GnRH.

Contrast agents (CAs) used in magnetic resonance imaging (MRI) are produced by chelating the metal gadolinium (Gd) with organic ligand molecules to form stable complexes. But, Gd3+ may dissociate from the CAs and subsequently might become toxic to its environment. Besides toxicity, it might inhibit calcium channels on cell membranes and this action could be detrimental to the cells governing biological development. The aim of this study was to investigate the interference of Gd3+ dechelated from the CAs by calcium signaling in the neuronal cells of gonadotropin-releasing hormone (GnRH), regulating puberty, and sexual development. The study used the mouse GT1-7 cell line as a model system, and Fura-2 based calcium imaging for detecting the interruption of intracellular calcium transport by the extracellular presence of Gd3+ as released from the CAs; gadodiamide and gadoterate meglumine, when the cells were stimulated in vitro culture by exposure to melatonin.The CA gadoterate meglumine interfered minimally with the calcium signaling, and thus its use is preferable in standard MRI exams. The release of Gd3+ from gadodiamide was significant and becomes of great concern as it may impact the neurophysiology of the neuronal cells in general, and gonadotropin production in particular, even in normal patients without nephrogenic systemic fibrosis. The toxicity induced by the influx of dechelated Gd3+ in the neurons of GnRH would have significant implications for puberty and reproductive functions.

Agomelatine potentiates anti-nociceptive effects of morphine in a mice model for diabetic neuropathy: involvement of NMDA receptor subtype NR1 within the raphe nucleus and periaqueductal grey.

OBJECTIVES: Opioid analgesics have been used for a long time in the treatment of acute and chronic pain. However, they have many side effects including tolerance development to a significant extent. Agomelatine, an atypical antidepressant, has been demonstrated to be effective in experimental studies on pain. However, the effect of agomelatine on morphine tolerance development and its mechanism of action are unknown. The antinociceptive effects of agomelatine, morphine and their combination were assessed in a mice model for painful diabetic neuropathy. The roles of glutamate ionotropic receptor N-methyl-D-aspartate (NMDA) type subunit-1 (GluN1) in raphe nucleus and periaqueductal gray (PAG) in the effect of agomelatine on neuropathic pain were also investigated in diabetic mice. METHODS: Agomelatine (10 mg/kg), morphine (10 mg/kg) and agomelatine + morphine were administered intraperitoneally for 15 consecutive days (twice per day), and the analgesic responses were assessed at days 1, 3, 6, 9, 12 and 15 in healthy and diabetic mice. Real time polymerase chain reaction (RT-PCR) was used to determine the changes in GluN1 expression. RESULTS: The tolerance development for morphine was evident, started at 6th day and remained thereafter, but not for agomelatine. GluN1 in raphe nucleus and PAG was upregulated in morphine treated but not in agomelatine-treated groups. DISCUSSION: The combination of agomelatine with morphine alone causes outlasting analgesic effects of repeated treatment, which can be interpreted as attenuated tolerance. Moreover, we also pointed out for the first time the modulatory effects of agomelatine on GluN1 expression in raphe nucleus and PAG after chronic morphine treatment. ABBREVIATIONS: Ca2+: Calcium; D2DR: Dopamine D2 receptor; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase; GluN1: Glutamate ionotropic receptor N-methyl-D-aspartate type subunit-1; 5-HT: 5-hydroxytryptamine; i.p.: intraperitoneal injection; MPE: Maximal possible effect; MT: Melatonin; NMDA: N-methyl-D-aspartate; NMDAR1: NMDA receptors-1; PAG: Periaqueductal grey; PKCγ: Protein kinase C gamma; RT-PCR: Real time polymerase chain reaction; STZ: Streptozotocin.

Chronic exposure to paroxetine or bupropion modulates the pubertal maturation and the reproductive system in female rats.

Antidepressant drugs are globally used to treat several psychiatric disorders in pediatric patients and their prescription has continued to increase in recent years, especially among girls. In addition to its well-known metabolic and gastrointestinal side effects, antidepressants can cause sexual dysfunction in adults. However, the effects of the antidepressants on puberty onset and reproductive system remain unclear in children and adolescents. Therefore, the goal of this study is to examine the effects of chronic postnatal antidepressant drugs, paroxetine or bupropion, treatments on puberty onset and reproductive system components in female rats weaned at postnatal day (PND) 21. Female rats (n = 10 for each group) were exposed to vehicle (0.2 mL of saline), paroxetine (3.6 mg/kg in 0.2 mL of saline) or bupropion (17 mg/kg in 0.2 mL of saline) daily by oral gavage from the PND 21 to PND 90-93. Chronic paroxetine or bupropion treatments advanced the puberty onset, but the difference was statistically significant in only the paroxetine group. The exposure to bupropion significantly decreased the serum anti-Müllerian hormone (AMH) levels and luteinizing hormone (LH) levels. There were increases in serum estradiol levels by both antidepressant treatments and the significance was found in only the paroxetine group. Consistent with these results, histopathologic changes were observed in the ovary and uterus tissues taken from both antidepressant-treated rats. The obtained results of chronic postnatal exposure to paroxetine or bupropion may change the timing of puberty onset and lead to disruption of reproductive functions in females.

Kisspeptin and RF9 prevent paroxetine-induced changes in some parameters of seminal vesicle fluid in the male rats.

The aim of the study was to examine possible impacts of paroxetine and agomelatine on the levels of some components that constitute the seminal vesicle fluid. As a second purpose, it was also aimed to examine how possible negative effects induced by paroxetine on seminal vesicle fluid components were affected by kisspeptin and RF9 (an RFamide-related peptide antagonist, RFRP). Forty-two male rats, aged 21 days, divided into six groups; control, sham, paroxetine, agomelatine, paroxetine + kisspeptin and paroxetine + RF9. Paroxetine (3.6 mg/kg) and agomelatine (10 mg/kg) were administrated by oral gavage. Kisspeptin (1 nmol) and RF9 (20 nmol) were administered intracerebroventricular (i.c.v). The experiments were ended on post-natal 120 days; fructose, vitamin E, sodium, potassium and magnesium levels were measured in seminal vesicle fluid. Fructose, vitamin E, magnesium and potassium levels were significantly decreased in seminal vesicle fluid from the rats treated with paroxetine but did not show significant differences following agomelatine administration. The co-administration of kisspeptin or RF9 with paroxetine prevented the paroxetine-induced negative effects on seminal vesicle fluid components. These results suggest that reduction in sperm fertilising ability caused by changes in seminal vesicle fluid can be seen in long-term antidepressant use. RF-9 and kisspeptin might have positive effects on long-term antidepressant use-induced infertility.

RF9: May it be a new therapeutic option for hypogonadotropic hypogonadism?

Hypogonadotropic hypogonadism (secondary hypogonadism), congenital or acquired, is a form of hypogonadism that is due to problems with either the hypothalamus or pituitary gland affecting gonadotropin levels. Pulsatile secretion of gonadotropin-releasing hormone (GnRH) by hypothalamus is a primer step to initiate the release of pituitary gonadotropins. Kisspeptin and gonadotropin-inhibitory hormone (GnIH) are accepted as two major players in the activation and inhibition of GnRH regarding the neuroendocrine functioning of the hypothalamic pituitary gonadal axis. Kisspeptin is known as the most potent activator of GnRH. Regarding the inhibition of GnRH, RF-amide-related peptide-3 (RFRP-3) is accepted as the mammalian orthologue of GnIH in avian species. RF9 (1-adamantane carbonyl-Arg-Phe-NH2) is an antagonist of RFRP-3/GnIH receptor (neuropeptide FF receptor 1 (NPFFR1; also termed as GPR147). In recent years, several studies have indicated that RF9 activates GnRH neurons and gonadotropins in a kisspeptin receptor (Kiss1r, formerly known as GPR54) dependent manner. These results suggest that RF9 may have a bimodal function as both an RFRP-3 antagonist and a kisspeptin agonist or it may be a kiss1r agonist rather than an RFRP-3/GnIH receptor antagonist. These interactions are possible because Kisspeptin and GnIH are members of the RF-amide family, and both possibilities are not far from explaining the potent gonadotropin stimulating effects of RF9. Therefore, we hypothesize that RF9 may be a new therapeutic option for the hypogonadotropic hypogonadism due to its potent GnRH stimulating effects. A constant or repeated administration of RF9 provides a sustained increase in plasma gonadotrophin levels. However, applications in the same way with GnRH analogues and kisspeptin may result in desensitization of the gonadotropic axis. The reasons reported above contribute to our hypothesis that RF9 may be a good option in the GnRH stimulating as a kisspeptin agonist. We suggest that further studies are needed to elucidate the potential effects of RF9 in the treatment of the hypogonadotropic hypogonadism.

Effects of gadolinium and gadolinium chelates on intracellular calcium signaling in sensory neurons.

Magnetic resonance imaging (MRI) employs gadolinium chelates as contrast agents to provide signal enhancement in radiological images. However, the instability of the chelates presents a challenge as the released gadolinium ion (Gd3+) from the chelates becomes toxic to the surrounding biological tissue. Chelates such as gadodiamide, gadoterate meglumine, gadobutrol and gadobenate dimeglumine are common contrast agents used in clinics. The release of Gd3+ from these agents have been reported previously using experimental setups involving water, but this study evaluates the release in cell culture of dorsal root ganglion (DRG) neurons as this model system is relevant to neuronal toxicity induced by these agents. DRG neurons were grown in primary culture following enzymatic and mechanical dissociation of ganglia from a 2-day-old neonatal Wistar rat. Using Fura-2 based calcium imaging, the effects of gadolinium chelates on free intracellular Ca2+ transport was assessed. The findings indicated that the contrast agent gadoterate meglumine exhibited the best performance in complex stability, independent of its concentration, and thus it must be taken into consideration in standard MRI exams and neuroimaging. The free Gd3+ released from the other agents is also of great concern as it may impact the neurophysiology of the neuronal cells in general, even in normal patients without nephrogenic systemic fibrosis.

Effects of long-term paroxetine or bupropion treatment on puberty onset, reproductive and feeding parameters in adolescent male rats.

Antidepressant use in adolescents has become more common in recent years. We have found several studies stating that prenatal antidepressant exposure can lead to delayed or earlier puberty onset but there was no study on postnatal paroxetine or bupropion. The main aim of this study was to investigate the effect of postnatal exposure to bupropion or paroxetine on puberty onset, reproductive and feeding results. The male rats (n = 8/group) aged 21 days were exposed to paroxetine (3.6 mg/kg) or bupropion (17 mg/kg) orally by gastric gavage every day from postnatal day 21-90. Also, control group received only saline orally as a vehicle. Postnatal exposure to bupropion or paroxetine delayed puberty onset compared to control group, but it was not significant. Sperm counts were significantly lower in the paroxetine and bupropion groups compared to control group. Sperm motility was significantly lower in only bupropion group. In addition, sperm motility was lower in paroxetine group, but it was not significant. In the histopathological examination, there was damage to the testicular structure in both treatments. Taken together, our result indicates that postnatal paroxetine or bupropion exposure may affect puberty onset and contribute to the impairment in fertility in male rats.

Lipopolysaccharide reduces gonadotrophin-releasing hormone (GnRH) gene expression: role of RFamide-related peptide-3 and kisspeptin.

RFamide-related peptide (RFRP)-3 reduces luteinising hormone (LH) secretion in rodents. Stress has been shown to upregulate the expression of the RFRP gene (Rfrp) with a concomitant reduction in LH secretion, but an effect on expression of the gonadotrophin-releasing hormone (GnRH) gene (Gnrh1) has not been shown. We hypothesised that lipopolysaccharide (LPS)-induced stress affects expression of Rfrp, the gene for kisspeptin (Kiss1) and/or Gnrh1, leading to suppression of LH levels in rats. Intracerebroventricular injections of RFRP-3 (0.1, 1, 5 nmol) or i.v. LPS (15µgkg-1) reduced LH levels. Doses of 1 and 5 nmol RFRP-3 were then administered to analyse gene expression by in situ hybridisation. RFRP-3 (5 nmol) had no effect on Gnrh1 or Kiss1 expression. LPS stress reduced GnRH and Kiss1 expression, without affecting Rfrp1 expression. These data indicate that LPS stress directly or indirectly reduces Gnrh1 expression, but this is unlikely to be due to a change in Rfrp1 expression.

Long-term metabolic cage housing increases anxiety/depression-related behaviours in adult male rats.

There are several reports on unfavourable effects of metabolic cage housing on animal welfare mainly due to the characteristic structures of these cages such as single housing and grid flooring. This study was aimed to compare the effects of long-term metabolic cage housing and conventional housing (normal grouped housing in standard cages) on the anxiety/depression-like behaviours in male rats. Anxiety/depression-related behaviours were evaluated by use of forced swimming test and open field test. Swimming and climbing were significantly lower and immobility duration higher in the metabolic cage group. In the open field test, total distance, mean velocity, time spent in the central area, zone transition, grooming, and rearing scores were significantly lower in the metabolic cage. Moreover, serum corticosterone level was higher in the metabolic cage group. The results of the study indicate that long-term metabolic cage housing may cause an increase in the anxiety- and depression-related behaviours in male rats.

Agomelatine modulates calcium signaling through protein kinase C and phospholipase C-mediated mechanisms in rat sensory neurons.

Agomelatine, a novel antidepressant exerting its effects through melatonergic and serotonergic systems, implicated to be effective against pain including neuropathic pain but without any knowledge of mechanism of action. To explore the possible role of agomelatine on nociceptive transmission at the peripheral level, the effects of agomelatine on intracellular calcium ([Ca2+ ]i ) signaling in peripheral neurons were investigated in cultured rat dorsal root ganglion (DRG) neurons. Using the fura-2-based calcium imaging technique, the effects of agomelatine on [Ca2+ ]i and roles of the second messenger-mediated pathways were assessed. Agomelatine caused [Ca2+ ]i signaling in a dose-dependent manner when tested at 10 and 100 µM concentration. Luzindole, a selective melatonin receptor antagonist, almost completely blocked the agomelatine-induced calcium signals. The agomelatine-induced calcium transients were also nearly abolished following pretreatment with the 100 ng/ml pertussis toxin, a Gi/o protein inhibitor. The stimulatory effects of agomelatine on [Ca2+ ]i transients were significantly reduced by applications of phospholipase C (PLC) and protein kinase C (PKC) blockers, 10 µM U73122, and 10 µM chelerythrine chloride, respectively. The obtained results of agomelatine-induced [Ca2+ ]i signals indicates that peripheral mechanisms are involved in analgesic effects of agomelatine. These mechanisms seems to involve G-protein-coupled receptor activation and PLC and PKC mediated mechanisms.