Brain RFamide Neuropeptides in Stress-Related Psychopathologies.

The RFamide peptide family is a group of proteins that share a common C-terminal arginine-phenylalanine-amide motif. To date, the family comprises five groups in mammals: neuropeptide FF, LPXRFamides/RFamide-related peptides, prolactin releasing peptide, QRFP, and kisspeptins. Different RFamide peptides have their own cognate receptors and are produced by different cell populations, although they all can also bind to neuropeptide FF receptors with different affinities. RFamide peptides function in the brain as neuropeptides regulating key aspects of homeostasis such as energy balance, reproduction, and cardiovascular function. Furthermore, they are involved in the organization of the stress response including modulation of pain. Considering the interaction between stress and various parameters of homeostasis, the role of RFamide peptides may be critical in the development of stress-related neuropathologies. This review will therefore focus on the role of RFamide peptides as possible key hubs in stress and stress-related psychopathologies. The neurotransmitter coexpression profile of RFamide-producing cells is also discussed, highlighting its potential functional significance. The development of novel pharmaceutical agents for the treatment of stress-related disorders is an ongoing need. Thus, the importance of RFamide research is underlined by the emergence of peptidergic and G-protein coupled receptor-based therapeutic targets in the pharmaceutical industry.

The Dopaminergic Cells in the Median Raphe Region Regulate Social Behavior in Male Mice.

According to previous studies, the median raphe region (MRR) is known to contribute significantly to social behavior. Besides serotonin, there have also been reports of a small population of dopaminergic neurons in this region. Dopamine is linked to reward and locomotion, but very little is known about its role in the MRR. To address that, we first confirmed the presence of dopaminergic cells in the MRR of mice (immunohistochemistry, RT-PCR), and then also in humans (RT-PCR) using healthy donor samples to prove translational relevance. Next, we used chemogenetic technology in mice containing the Cre enzyme under the promoter of the dopamine transporter. With the help of an adeno-associated virus, designer receptors exclusively activated by designer drugs (DREADDs) were expressed in the dopaminergic cells of the MRR to manipulate their activity. Four weeks later, we performed an extensive behavioral characterization 30 min after the injection of the artificial ligand (Clozapine-N-Oxide). Stimulation of the dopaminergic cells in the MRR decreased social interest without influencing aggression and with an increase in social discrimination. Additionally, inhibition of the same cells increased the friendly social behavior during social interaction test. No behavioral changes were detected in anxiety, memory or locomotion. All in all, dopaminergic cells were present in both the mouse and human samples from the MRR, and the manipulation of the dopaminergic neurons in the MRR elicited a specific social response.

Prolactin-Releasing Peptide Contributes to Stress-Related Mood Disorders and Inhibits Sleep/Mood Regulatory Melanin-Concentrating Hormone Neurons in Rats.

Stress disorders impair sleep and quality of life; however, their pathomechanisms are unknown. Prolactin-releasing peptide (PrRP) is a stress mediator; we therefore hypothesized that PrRP may be involved in the development of stress disorders. PrRP is produced by the medullary A1/A2 noradrenaline (NA) cells, which transmit stress signals to forebrain centers, and by non-NA cells in the hypothalamic dorsomedial nucleus. We found in male rats that both PrRP and PrRP-NA cells innervate melanin-concentrating hormone (MCH) producing neurons in the dorsolateral hypothalamus (DLH). These cells serve as a key hub for regulating sleep and affective states. Ex vivo, PrRP hyperpolarized MCH neurons and further increased the hyperpolarization caused by NA. Following sleep deprivation, intracerebroventricular PrRP injection reduced the number of REM sleep-active MCH cells. PrRP expression in the dorsomedial nucleus was upregulated by sleep deprivation, while downregulated by REM sleep rebound. Both in learned helplessness paradigm and after peripheral inflammation, impaired coping with sustained stress was associated with (1) overactivation of PrRP cells, (2) PrRP protein and receptor depletion in the DLH, and (3) dysregulation of MCH expression. Exposure to stress in the PrRP-insensitive period led to increased passive coping with stress. Normal PrRP signaling, therefore, seems to protect animals against stress-related disorders. PrRP signaling in the DLH is an important component of the PrRP's action, which may be mediated by MCH neurons. Moreover, PrRP receptors were downregulated in the DLH of human suicidal victims. As stress-related mental disorders are the leading cause of suicide, our findings may have particular translational relevance.SIGNIFICANCE STATEMENT Treatment resistance to monoaminergic antidepressants is a major problem. Neuropeptides that modulate the central monoaminergic signaling are promising targets for developing alternative therapeutic strategies. We found that stress-responsive prolactin-releasing peptide (PrRP) cells innervated melanin-concentrating hormone (MCH) neurons that are crucial in the regulation of sleep and mood. PrRP inhibited MCH cell activity and enhanced the inhibitory effect evoked by noradrenaline, a classic monoamine, on MCH neurons. We observed that impaired PrRP signaling led to failure in coping with chronic/repeated stress and was associated with altered MCH expression. We found alterations of the PrRP system also in suicidal human subjects. PrRP dysfunction may underlie stress disorders, and fine-tuning MCH activity by PrRP may be an important part of the mechanism.

Hypothalamic Nesfatin-1 Resistance May Underlie the Development of Type 2 Diabetes Mellitus in Maternally Undernourished Non-obese Rats.

Intrauterine growth retardation (IUGR) poses a high risk for developing late-onset, non-obese type 2 diabetes (T2DM). The exact mechanism underlying this phenomenon is unknown, although the contribution of the central nervous system is recognized. The main hypothalamic nuclei involved in the homeostatic regulation express nesfatin-1, an anorexigenic neuropeptide and identified regulator of blood glucose level. Using intrauterine protein restricted rat model (PR) of IUGR, we investigated, whether IUGR alters the function of nesfatin-1. We show that PR rats develop fat preference and impaired glucose homeostasis by adulthood, while the body composition and caloric intake of normal nourished (NN) and PR rats are similar. Plasma nesfatin-1 levels are unaffected by IUGR in both neonates and adults, but pro-nesfatin-1 mRNA expression is upregulated in the hypothalamus of adult PR animals. We find that centrally injected nesfatin-1 inhibits the fasting induced neuronal activation in the hypothalamic arcuate nucleus in adult NN rats. This effect of nesfatin-1 is not seen in PR rats. The anorexigenic effect of centrally injected nesfatin-1 is also reduced in adult PR rats. Moreover, chronic central nesfatin-1 administration improves the glucose tolerance and insulin sensitivity in NN rats but not in PR animals. Birth dating of nesfatin-1 cells by bromodeoxyuridine (BrDU) reveals that formation of nesfatin-1 cells in the hypothalamus of PR rats is disturbed. Our results suggest that adult PR rats acquire hypothalamic nesfatin-1-resistance, probably due to the altered development of the hypothalamic nesfatin-1 cells. Hypothalamic nesfatin-1-resistance, in turn, may contribute to the development of non-obese type T2DM.

Rescue of Vasopressin Synthesis in Magnocellular Neurons of the Supraoptic Nucleus Normalises Acute Stress-Induced Adrenocorticotropin Secretion and Unmasks an Effect on Social Behaviour in Male Vasopressin-Deficient Brattleboro Rats.

The relevance of vasopressin (AVP) of magnocellular origin to the regulation of the endocrine stress axis and related behaviour is still under discussion. We aimed to obtain deeper insight into this process. To rescue magnocellular AVP synthesis, a vasopressin-containing adeno-associated virus vector (AVP-AAV) was injected into the supraoptic nucleus (SON) of AVP-deficient Brattleboro rats (di/di). We compared +/+, di/di, and AVP-AAV treated di/di male rats. The AVP-AAV treatment rescued the AVP synthesis in the SON both morphologically and functionally. It also rescued the peak of adrenocorticotropin release triggered by immune and metabolic challenges without affecting corticosterone levels. The elevated corticotropin-releasing hormone receptor 1 mRNA levels in the anterior pituitary of di/di-rats were diminished by the AVP-AAV-treatment. The altered c-Fos synthesis in di/di-rats in response to a metabolic stressor was normalised by AVP-AAV in both the SON and medial amygdala (MeA), but not in the central and basolateral amygdala or lateral hypothalamus. In vitro electrophysiological recordings showed an AVP-induced inhibition of MeA neurons that was prevented by picrotoxin administration, supporting the possible regulatory role of AVP originating in the SON. A memory deficit in the novel object recognition test seen in di/di animals remained unaffected by AVP-AAV treatment. Interestingly, although di/di rats show intact social investigation and aggression, the SON AVP-AAV treatment resulted in an alteration of these social behaviours. AVP released from the magnocellular SON neurons may stimulate adrenocorticotropin secretion in response to defined stressors and might participate in the fine-tuning of social behaviour with a possible contribution from the MeA.

Chemical characterization of pineal neurons in perinatal rats.

Ample evidence indicates that in several mammalian species the pineal body contains neurons. In adult white albino rats neurons are not present in the pineal body; however, in perinatal rats many neurons were described. It was demonstrated that in adult mammalian species the pineal neurons contained some neuropeptides and neurotransmitters such as leu-enkephalin, met-enkephalin, substance-P, somatostatin and γ-aminobutiric acid. Oxytocin, vasopressin mRNAs and peptides were also demonstrated. No data are available on the chemical nature of the neurons in perinatal rats. In the present experiment we used immunohistochemistry to clarify this issue. After paraformaldehyde fixation frozen sections were prepared and stained for immunoreactivities of several neuropeptides and neurotransmitters. Dopamine ß-hydroxylase, neuropeptide-Y, vesicular acetylcholine transporter, vesicular glutamate transporter and calcitonin gene-related peptide antibodies were able to stain fibers. According to previous data these fibers may be sympathetic, parasympathetic or sensory. Vesicular glutamate transporter antibody may stain pinealocytes as well. Some cells were immunoreactive for substance-P, oxytocin, vasopressin, leu-enkefalin and glutamic acid decarboxylase. These immnoreactivities showed colocalization with neuron-specific nuclear protein immunoreactivity indicating that these cells were neurons. Calbindin was observed in oval and elongated cells resembling pinealocytes. Based on the results obtained in adult mammals, the pineal neurons may be analogue to retinal ganglion cells, or they may function as interneurons in the retino-pinealo-retinal neuronal circuit or peptidergic neurons may influence pinealocytes in a paracrine manner.

Angiotensin II-Induced Cardiac Effects Are Modulated by Endocannabinoid-Mediated CB1 Receptor Activation.

Angiotensin II (Ang II) has various cardiac effects and causes vasoconstriction. Ang II activates the type-1 angiotensin receptor-Gq/11 signaling pathway resulting in the release of 2-arachidonoylglycerol (2-AG). We aimed to investigate whether cardiac Ang II effects are modulated by 2-AG-release and to identify the role of type-1 cannabinoid receptors (CB1R) in these effects. Expression of CB1R in rat cardiac tissue was confirmed by immunohistochemistry. To characterize short-term Ang II effects, increasing concentrations of Ang II (10-9-10-7 M); whereas to assess tachyphylaxis, repeated infusions of Ang II (10-7 M) were administered to isolated Langendorff-perfused rat hearts. Ang II infusions caused a decrease in coronary flow and ventricular inotropy, which was more pronounced during the first administration. CB agonist 2-AG and WIN55,212-2 administration to the perfusate enhanced coronary flow. The flow-reducing effect of Ang II was moderated in the presence of CB1R blocker O2050 and diacylglycerol-lipase inhibitor Orlistat. Our findings indicate that Ang II-induced cardiac effects are modulated by simultaneous CB1R-activation, most likely due to 2-AG-release during Ang II signalling. In this combined effect, the response to 2-AG via cardiac CB1R may counteract the positive inotropic effect of Ang II, which may decrease metabolic demand and augment Ang II-induced coronary vasoconstriction.

Colocalized neurotransmitters in the hindbrain cooperate in adaptation to chronic hypernatremia.

Chronic hypernatremia activates the central osmoregulatory mechanisms and inhibits the function of the hypothalamic-pituitary-adrenal (HPA) axis. Noradrenaline (NE) release into the periventricular anteroventral third ventricle region (AV3V), the supraoptic (SON) and hypothalamic paraventricular nuclei (PVN) from efferents of the caudal ventrolateral (cVLM) and dorsomedial (cDMM) medulla has been shown to be essential for the hypernatremia-evoked responses and for the HPA response to acute restraint. Notably, the medullary NE cell groups highly coexpress prolactin-releasing peptide (PrRP) and nesfatin-1/NUCB2 (nesfatin), therefore, we assumed they contributed to the reactions to chronic hypernatremia. To investigate this, we compared two models: homozygous Brattleboro rats with hereditary diabetes insipidus (DI) and Wistar rats subjected to chronic high salt solution (HS) intake. HS rats had higher plasma osmolality than DI rats. PrRP and nesfatin mRNA levels were higher in both models, in both medullary regions compared to controls. Elevated basal tyrosine hydroxylase (TH) expression and impaired restraint-induced TH, PrRP and nesfatin expression elevations in the cVLM were, however, detected only in HS, but not in DI rats. Simultaneously, only HS rats exhibited classical signs of chronic stress and severely blunted hormonal reactions to acute restraint. Data suggest that HPA axis responsiveness to restraint depends on the type of hypernatremia, and on NE capacity in the cVLM. Additionally, NE and PrRP signalization primarily of medullary origin is increased in the SON, PVN and AV3V in HS rats. This suggests a cooperative action in the adaptation responses and designates the AV3V as a new site for PrRP's action in hypernatremia.

Reward-representing D1-type neurons in the medial shell of the accumbens nucleus regulate palatable food intake.

BACKGROUND/OBJECTIVES: Dysfunction in reward-related aspects of feeding, and consequent overeating in humans, is a major contributor to obesity. Intrauterine undernutrition and overnutrition are among the predisposing factors, but the exact mechanism of how overeating develops is still unclear. Consummatory behavior is regulated by the medial shell (mSh) of the accumbens nucleus (Nac) through direct connections with the rostral part of the lateral hypothalamic area (LHA). Our aim was to investigate whether an altered Nac-LHA circuit may underlie hyperphagic behavior. SUBJECTS/METHODS: Intrauterine protein-restricted (PR) male Wistar rats were used as models for hyperphagia. The experiments were performed using young adult control (normally nourished) and PR animals. Sweet condensed milk (SCM) served as a reward to test consumption and subsequent activation (Fos+) of Nac and LHA neurons. Expression levels of type 1 and 2 dopamine receptors (D1R, D2R) in the Nac, as well as tyrosine hydroxylase (TH) levels in the ventral tegmental area, were determined. The D1R agonist SKF82958 was injected into the mSh-Nac of control rats to test the effect of D1R signaling on SCM intake and neuronal cell activation in the LHA. RESULTS: A group of food reward-representing D1R+ neurons was identified in the mSh-Nac. Activation (Fos+) of these neurons was highly proportional to the consumed palatable food. D1R agonist treatment attenuated SCM intake and diminished the number of SCM-activated cells in the LHA. Hyperphagic PR rats showed increased intake of SCM, reduced D1R expression, and an impaired response to SCM-evoked neuronal activation in the mSh-Nac, accompanied by an elevated number of Fos+ neurons in the LHA compared to controls. CONCLUSIONS: Sensitivity of food reward-representing neurons in the mSh-Nac determines the level of satisfaction that governs cessation of consumption, probably through connections with the LHA. D1R signaling is a key element in this function, and is impaired in obesity-prone rats.

Glial cell type-specific changes in spinal dipeptidyl peptidase 4 expression and effects of its inhibitors in inflammatory and neuropatic pain.

Altered pain sensations such as hyperalgesia and allodynia are characteristic features of various pain states, and remain difficult to treat. We have shown previously that spinal application of dipeptidyl peptidase 4 (DPP4) inhibitors induces strong antihyperalgesic effect during inflammatory pain. In this study we observed low level of DPP4 mRNA in the rat spinal dorsal horn in physiological conditions, which did not change significantly either in carrageenan-induced inflammatory or partial nerve ligation-generated neuropathic states. In naïve animals, microglia and astrocytes expressed DPP4 protein with one and two orders of magnitude higher than neurons, respectively. DPP4 significantly increased in astrocytes during inflammation and in microglia in neuropathy. Intrathecal application of two DPP4 inhibitors tripeptide isoleucin-prolin-isoleucin (IPI) and the antidiabetic drug vildagliptin resulted in robust opioid-dependent antihyperalgesic effect during inflammation, and milder but significant opioid-independent antihyperalgesic action in the neuropathic model. The opioid-mediated antihyperalgesic effect of IPI was exclusively related to mu-opioid receptors, while vildagliptin affected mainly delta-receptor activity, although mu- and kappa-receptors were also involved. None of the inhibitors influenced allodynia. Our results suggest pathology and glia-type specific changes of DPP4 activity in the spinal cord, which contribute to the development and maintenance of hyperalgesia and interact with endogenous opioid systems.

Interaction between p22phox and Nox4 in the endoplasmic reticulum suggests a unique mechanism of NADPH oxidase complex formation.

The p22phox protein is an essential component of the phagocytic- and inner ear NADPH oxidases but its relationship to other Nox proteins is less clear. We have studied the role of p22phox in the TGF-ß1-stimulated H2O2 production of primary human and murine fibroblasts. TGF-ß1 induced H2O2 release of the examined cells, and the response was dependent on the expression of both Nox4 and p22phox. Interestingly, the p22phox protein was present in the absence of any detectable Nox/Duox expression, and the p22phox level was unaffected by TGF-ß1. On the other hand, Nox4 expression was dependent on the presence of p22phox, establishing an asymmetrical relationship between the two proteins. Nox4 and p22phox proteins localized to the endoplasmic reticulum and their distribution was unaffected by TGF-ß1. We used a chemically induced protein dimerization method to study the orientation of p22phox and Nox4 in the endoplasmic reticulum membrane. This technique is based on the rapamycin-mediated heterodimerization of the mammalian FRB domain with the FK506 binding protein. The results of these experiments suggest that the enzyme complex produces H2O2 into the lumen of the endoplasmic reticulum, indicating that Nox4 contributes to the development of the oxidative milieu within this organelle.

Secretagogin-dependent matrix metalloprotease-2 release from neurons regulates neuroblast migration.

The rostral migratory stream (RMS) is viewed as a glia-enriched conduit of forward-migrating neuroblasts in which chemorepulsive signals control the pace of forward migration. Here we demonstrate the existence of a scaffold of neurons that receive synaptic inputs within the rat, mouse, and human fetal RMS equivalents. These neurons express secretagogin, a Ca2+-sensor protein, to execute an annexin V-dependent externalization of matrix metalloprotease-2 (MMP-2) for reconfiguring the extracellular matrix locally. Mouse genetics combined with pharmacological probing in vivo and in vitro demonstrate that MMP-2 externalization occurs on demand and that its loss slows neuroblast migration. Loss of function is particularly remarkable upon injury to the olfactory bulb. Cumulatively, we identify a signaling cascade that provokes structural remodeling of the RMS through recruitment of MMP-2 by a previously unrecognized neuronal constituent. Given the life-long presence of secretagogin-containing neurons in human, this mechanism might be exploited for therapeutic benefit in rescue strategies.

Endocannabinoid-mediated modulation of Gq/11 protein-coupled receptor signaling-induced vasoconstriction and hypertension.

Activation of G protein-coupled receptors (GPCRs) can induce vasoconstriction via calcium signal-mediated and Rho-dependent pathways. Earlier reports have shown that diacylglycerol produced during calcium signal generation can be converted to an endocannabinoid, 2-arachidonoylglycerol (2-AG). Our aim was to provide evidence that GPCR signaling-induced 2-AG production and activation of vascular type1 cannabinoid receptors (CB1R) is capable of reducing agonist-induced vasoconstriction and hypertension. Rat and mouse aortic rings were examined by myography. Vascular expression of CB1R was demonstrated with immunohistochemistry. Rat aortic vascular smooth muscle cells (VSMCs) were cultured for calcium measurements and 2-AG-determination. Inhibition or genetic loss of CB1Rs enhanced vasoconstriction induced by angiotensin II (AngII) or phenylephrine (Phe), but not by prostaglandin(PG)F2α. AngII-induced vasoconstriction was augmented by inhibition of diacylglycerol lipase (tetrahydrolipstatin) and was attenuated by inhibition of monoacylglycerol lipase (JZL184) suggesting a functionally relevant role for endogenously produced 2-AG. In Gαq/11-deficient mice vasoconstriction was absent to AngII or Phe, which activate Gq/11-coupled receptors, but was maintained in response to PGF2α. In VSMCs, AngII-stimulated 2-AG-formation was inhibited by tetrahydrolipstatin and potentiated by JZL184. CB1R inhibition increased the sustained phase of AngII-induced calcium signal. Pharmacological or genetic loss of CB1R function augmented AngII-induced blood pressure rise in mice. These data demonstrate that vasoconstrictor effect of GPCR agonists is attenuated via Gq/11-mediated vascular endocannabinoid formation. Agonist-induced endocannabinoid-mediated CB1R activation is a significant physiological modulator of vascular tone. Thus, the selective modulation of GPCR signaling-induced endocannabinoid release has a therapeutic potential in case of increased vascular tone and hypertension.

Vasopressin deficiency diminishes acute and long-term consequences of maternal deprivation in male rat pups.

Early life events have special importance in the development as postnatal environmental alterations may permanently affect the lifetime vulnerability to diseases. For the interpretation of the long-term consequences it is important to understand the immediate effects. As the role of vasopressin in hypothalamic-pituitary-adrenal axis regulation as well as in affective disorders seem to be important we addressed the question whether the congenital lack of vasopressin will modify the stress reactivity of the pups and will influence the later consequences of single 24h maternal deprivation (MD) on both stress-reactivity and stress-related behavioral changes. Vasopressin-producing (di/+) and deficient (di/di) Brattleboro rat were used. In 10-day-old pups MD induced a remarkable corticosterone rise in both genotypes without adrenocorticotropin (ACTH) increase in di/di rats. Studying the later consequences at around weaning (25-35-day-old rats) we found somatic and hormonal alterations (body weight reduction, dysregulation of the stress axis) which were not that obvious in di/di rats. The more anxious state of MD rats was not detectable in di/di rats both at weaning and in adulthood (7-12-week-old). The lack of vasopressin abolished all chronic stress and anxiety-like tendencies both at weaning and in adulthood probably as a consequence of reduced ACTH rise immediately after MD in pups. This finding suggests that postnatal stress-induced ACTH rise may have long-term developmental consequences.

Peroxidasin-like protein: a novel peroxidase homologue in the human heart.

AIMS: Peroxidases serve diverse biological functions including well-characterized activities in host defence and hormone biosynthesis. More recently, peroxidasin (PXDN) was found to be involved in collagen IV cross-linking in the extracellular matrix (ECM). The aim of this study was to characterize the expression and function of peroxidasin-like protein (PXDNL), a previously unknown peroxidase homologue. METHODS AND RESULTS: We cloned the PXDNL cDNA from the human heart and identified its expression pattern by northern blot, in situ hybridization, and immunohistochemistry. PXDNL is expressed exclusively in the heart and it has evolved to lose its peroxidase activity. The protein is produced by cardiomyocytes and localizes to cell-cell junctions. We also demonstrate that PXDNL can form a complex with PXDN and antagonizes its peroxidase activity. Furthermore, we show an increased expression of PXDNL in the failing myocardium. CONCLUSION: PXDNL is a unique component of the heart with a recently evolved inactivation of peroxidase function. The elevation of PXDNL levels in the failing heart may contribute to ECM dysregulation due to its antagonism of PXDN function.

Nesfatin-1/NUCB2 as a potential new element of sleep regulation in rats.

STUDY OBJECTIVES: Millions suffer from sleep disorders that often accompany severe illnesses such as major depression; a leading psychiatric disorder characterized by appetite and rapid eye movement sleep (REMS) abnormalities. Melanin-concentrating hormone (MCH) and nesfatin-1/NUCB2 (nesfatin) are strongly co - expressed in the hypothalamus and are involved both in food intake regulation and depression. Since MCH was recognized earlier as a hypnogenic factor, we analyzed the potential role of nesfatin on vigilance. DESIGN: We subjected rats to a 72 h-long REMS deprivation using the classic flower pot method, followed by a 3 h-long 'rebound sleep'. Nesfatin mRNA and protein expressions as well as neuronal activity (Fos) were measured by quantitative in situ hybridization technique, ELISA and immunohistochemistry, respectively, in 'deprived' and 'rebound' groups, relative to controls sacrificed at the same time. We also analyzed electroencephalogram of rats treated by intracerebroventricularly administered nesfatin-1, or saline. RESULTS: REMS deprivation downregulated the expression of nesfatin (mRNA and protein), however, enhanced REMS during 'rebound' reversed this to control levels. Additionally, increased transcriptional activity (Fos) was demonstrated in nesfatin neurons during 'rebound'. Centrally administered nesfatin-1 at light on reduced REMS and intermediate stage of sleep, while increased passive wake for several hours and also caused a short-term increase in light slow wave sleep. CONCLUSIONS: The data designate nesfatin as a potential new factor in sleep regulation, which fact can also be relevant in the better understanding of the role of nesfatin in the pathomechanism of depression.

Distribution of secretin receptors in the rat central nervous system: an in situ hybridization study.

Secretin shows a wide distribution in the brain. Functional significance of central secretin is stressed since it has been associated with autism and schizophrenia. The presence of the secretin receptor was previously demonstrated in the brain by different methods. Neurons in the cerebellum, hypothalamic paraventricular and supraoptic nuclei, and in the vascular organ of lamina terminalis were shown to express secretin receptor mRNA by using in situ hybridization with digoxigenin-labeled probe. In this work, we used a very sensitive radioactive in situ hybridization technique and systematically mapped the expression of secretin receptor mRNA in the brain. The densest labeling was observed in the nucleus of solitary tract and in the laterodorsal thalamic nucleus, where decreasing number of receptors was seen in the vascular organ of lamina terminalis, and the lateral habenular complex, and then in the supraoptic nucleus. Only a few scattered labeled cells were observed in the median frontal gyrus, entorhinal cortex, hypothalamic paraventricular nucleus, perifornical region, lateral hypothalamic area, head of the caudate nucleus, spinal trigeminal nucleus, and cerebellum. Secretin receptor mRNA showed a far wider distribution than was known before, suggesting a more significant functional relevance than thought earlier.

Angiotensin II induces vascular endocannabinoid release, which attenuates its vasoconstrictor effect via CB1 cannabinoid receptors.

In the vascular system angiotensin II (Ang II) causes vasoconstriction via the activation of type 1 angiotensin receptors. Earlier reports have shown that in cellular expression systems diacylglycerol produced during type 1 angiotensin receptor signaling can be converted to 2-arachidonoylglycerol, an important endocannabinoid. Because activation of CB(1) cannabinoid receptors (CB(1)R) induces vasodilation and reduces blood pressure, we have tested the hypothesis that Ang II-induced 2-arachidonoylglycerol release can modulate its vasoconstrictor action in vascular tissue. Rat and mouse skeletal muscle arterioles and mouse saphenous arteries were isolated, pressurized, and subjected to microangiometry. Vascular expression of CB(1)R was demonstrated using Western blot and RT-PCR. In accordance with the functional relevance of these receptors WIN55212, a CB(1)R agonist, caused vasodilation, which was absent in CB(1)R knock-out mice. Inhibition of CB(1)Rs using O2050, a neutral antagonist, enhanced the vasoconstrictor effect of Ang II in wild type but not in CB(1)R knock-out mice. Inverse agonists of CB(1)R (SR141716 and AM251) and inhibition of diacylglycerol lipase using tetrahydrolipstatin also augmented the Ang II-induced vasoconstriction, suggesting that endocannabinoid release modulates this process via CB(1)R activation. This effect was independent of nitric-oxide synthase activity and endothelial function. These data demonstrate that Ang II stimulates vascular endocannabinoid formation, which attenuates its vasoconstrictor effect, suggesting that endocannabinoid release from the vascular wall and CB(1)R activation reduces the vasoconstrictor and hypertensive effects of Ang II.

Intranasal application of secretin, similarly to intracerebroventricular administration, influences the motor behavior of mice probably through specific receptors.

Secretin and its receptors show wide distribution in the central nervous system. It was demonstrated previously that intravenous (i.v.) and intracerebroventricular (i.c.v.) application of secretin influenced the behavior of rat, mouse, and human. In our previous experiment, we used a special animal model, Japanese waltzing mice (JWM). These animals run around without stopping (the ambulation distance is very limited) and they do not bother with their environment. The i.c.v. secretin attenuated this hyperactive repetitive movement. In the present work, the effect of i.c.v. and intranasal (i.n.) application of secretin was compared. We have also looked for the presence of secretin receptors in the brain structures related to motor functions. Two micrograms of i.c.v. secretin improved the horizontal movement of JWM, enhancing the ambulation distance. It was nearly threefold higher in treated than in control animals. The i.n. application of secretin to the left nostril once or twice a day or once for 3 days more effectively enhanced the ambulation distance than i.c.v. administration. When secretin was given twice a day for 3 days it had no effect. Secretin did not improve the explorative behavior (the rearing), of JWM. With the use of in situ hybridization, we have found very dense secretin receptor labeling in the cerebellum. In the primary motor cortex and in the striatum, only a few labeled cells were seen. It was supposed that secretin exerted its effect through specific receptors, mainly present in the cerebellum.