Poly(I:C) promotes neurotoxic amyloid ß accumulation through reduced degradation by decreasing neprilysin protein levels in astrocytes.

Inflammation associated with viral infection of the nervous system has been involved in the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease (AD) and multiple sclerosis. Polyinosinic:polycytidylic acid (poly[I:C]) is a Toll-like receptor 3 (TLR3) agonist that mimics the inflammatory response to systemic viral infections. Despite growing recognition of the role of glial cells in AD pathology, their involvement in the accumulation and clearance of amyloid ß (Aß) in the brain of patients with AD is poorly understood. Neprilysin (NEP) and insulin-degrading enzyme (IDE) are the main Aß-degrading enzymes in the brain. This study investigated whether poly(I:C) regulated Aß degradation and neurotoxicity by modulating NEP and IDE protein levels through TLR3 in astrocytes. To this aim, primary rat primary astrocyte cultures were treated with poly(I:C) and inhibitors of the TLR3 signaling. Protein levels were assessed by Western blot. Aß toxicity to primary neurons was measured by lactate dehydrogenase release. Poly(I:C) induced a significant decrease in NEP levels on the membrane of astrocytes as well as in the culture medium. The degradation of exogenous Aß was markedly delayed in poly(I:C)-treated astrocytes. This delay significantly increased the neurotoxicity of exogenous Aß1-42. Altogether, these results suggest that viral infections induce Aß neurotoxicity by decreasing NEP levels in astrocytes and consequently preventing Aß degradation.

Protein kinases A and C regulate amyloid-ß degradation by modulating protein levels of neprilysin and insulin-degrading enzyme in astrocytes.

The pathology of sporadic Alzheimer's disease is hallmarked by altered signal transduction via the neurotransmitter receptor-G-protein-mediated protein kinase A (PKA) and protein kinase C (PKC) pathways. Because the accumulation of amyloid-ß (Aß) depends on its rates of synthesis and clearance, the metabolic pathway of Aß in the brain and the entire body warrants exploration. The two major enzymes involved in Aß degradation in the brain are believed to be the neprilysin and insulin-degrading enzyme (IDE). This study investigated whether PKA and PKC regulate the degradation of Aß by modulating the protein levels of neprilysin and IDE in astrocytes. Activation of PKA induced a significant decrease in neprilysin protein levels in cultured astrocytes, whereas activation of PKC induced a significant decrease in the protein level of neprilysin and an increase in the protein level of IDE. Following activation of PKC, the reduction of neprilysin was achieved by its secretion into the culture media. Moreover, PKA-activated astrocytes significantly delayed the degradation of exogenous Aß, whereas PKC-activated astrocytes significantly facilitated its degradation. These results suggest that PKA and PKC regulate Aß degradation in astrocytes through a decrease in the protein level of neprilysin and an increase in neprilysin secretion and protein levels of IDE, respectively.

Insulin-signaling Pathway Regulates the Degradation of Amyloid ß-protein via Astrocytes.

Alzheimer's disease (AD) has been considered as a metabolic dysfunction disease associated with impaired insulin signaling. Determining the mechanisms underlying insulin signaling dysfunction and resistance in AD will be important for its treatment. Impaired clearance of amyloid-ß peptide (Aß) significantly contributes to amyloid accumulation, which is typically observed in the brain of AD patients. Reduced expression of important Aß-degrading enzymes in the brain, such as neprilysin (NEP) and insulin-degrading enzyme (IDE), can promote Aß deposition in sporadic late-onset AD patients. Here, we investigated whether insulin regulates the degradation of Aß by inducing expression of NEP and IDE in cultured astrocytes. Treatment of astrocytes with insulin significantly reduced cellular NEP levels, but increased IDE expression. The effects of insulin on the expression of NEP and IDE involved activation of an extracellular signal-regulated kinase (ERK)-mediated pathway. The reduction in cellular NEP levels was associated with NEP secretion into the culture medium, whereas IDE was increased in the cell membranes. Moreover, insulin-treated astrocytes significantly facilitated the degradation of exogenous Aß within the culture medium. Interestingly, pretreatment of astrocytes with an ERK inhibitor prior to insulin exposure markedly inhibited insulin-induced degradation of Aß. These results suggest that insulin exposure enhanced Aß degradation via an increase in NEP secretion and IDE expression in astrocytes, via activation of the ERK-mediated pathway. The inhibition of insulin signaling pathways delayed Aß degradation by attenuating alterations in NEP and IDE levels and competition with insulin and Aß. Our results provide further insight into the pathological relevance of insulin resistance in AD development.

Anaphylactic hypotension causes renal and adrenal sympathoexcitaion and induces c-fos in the hypothalamus and medulla oblongata.

NEW FINDINGS: What is the central question of this study? Whether anaphylaxis affects sympathetic outflows to the brown adipose tissue (BAT) and adrenal gland and whether anaphylaxis affects some brain areas in association with sympathetic regulation. What is the main finding and its importance? Sympathoexcitatory responses to anaphylaxis occurred regionally in the kidney and adrenal gland, but not in the thermogenesis-related BAT. Further, anaphylactic hypotension also caused increase in c-fos immunoreactivity in the hypothalamic and medullary areas. Moreover, catecholaminergic neurons of the brainstem cause adrenal sympathoexcitation in a baroreceptor-independent manner. ABSTRACT: We previously reported that sympathetic nerve activity (SNA) to the kidney and the hindlimb increases during anaphylactic hypotension in anaesthetized rats. Based on this evidence, we examined effects of anaphylactic hypotension on SNA to the brown adipose tissue (BAT), and the adrenal gland and kidney in anaesthetized rats. We demonstrated that adrenal and renal SNA, but not BAT-SNA, were stimulated. In addition, the effects of anaphylaxis on neural activities of the hypothalamic and medullary nuclei, which are candidates for relaying efferent SNA to the peripheral organs, were investigated via immunohistochemical staining of c-fos. Anaphylaxis increased c-fos expression in the neurons of the paraventricular nucleus (PVN) of the hypothalamus and in those of the nucleus tractus solitarii (NTS) and rostral ventrolateral medulla (RVLM) of the medulla oblongata; c-fos was expressed in γ-aminobutyric acid (GABA)-ergic neurons of the NTS and in the catecholaminergic neurons of the RVLM. In addition, c-fos expression in the rostral NTS and mid NTS during anaphylaxis was reduced by sinoaortic baroreceptor denervation; however, increased c-fos expression in the caudal NTS and RVLM or adrenal sympathoexcitation were not affected by sinoaortic baroreceptor denervation. These results indicated that anaphylactic hypotension activates the hypothalamic PVN and the medullary NTS and RVLM independently of the baroreflex pathway. Further, it stimulated efferent SNA to the adrenal gland and kidney to restore blood pressure.

Epigallocatechin gallate induces extracellular degradation of amyloid ß-protein by increasing neprilysin secretion from astrocytes through activation of ERK and PI3K pathways.

Amyloid-ß (Aß) production and clearance in the brain is a crucial focus of investigations into the pathogenesis of Alzheimer disease. Imbalance between production and clearance leads to accumulation of Aß. The important Aß-degrading enzymes in the brain are neprilysin (NEP) and insulin-degrading enzyme (IDE), and defective enzyme expression may facilitate Aß deposition in sporadic late-onset AD patients. It has been suggested that epigallocatechin gallate (EGCG), a member of the catechin family, might be an effective treatment for AD, because it has been shown to elevate NEP expression. Therefore, we examined whether catechins, which are functional components of common foods, could regulate the degradation of Aß by inducing NEP and IDE expression. We also investigated the role of catechins in activating intracellular signal transduction in astrocytes. Treatment of cultured rat astrocytes with EGCG significantly reduced the expression of NEP, but not IDE, in a concentration- and time-dependent manner. NEP expression in cultured astrocytes was suppressed by activation of extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K), and reduced NEP expression was accompanied by an increase of NEP release into the extracellular space (culture medium). Moreover, culture medium from EGCG-treated astrocytes facilitated the degradation of exogenous Aß. These results suggest that EGCG may have a beneficial effect on AD by activating ERK-and PI3K-mediated pathways in astrocytes, thus increasing astrocyte secretion of NEP and facilitating degradation of Aß.

Dynamical mechanisms of phase-2 early afterdepolarizations in human ventricular myocytes: insights from bifurcation analyses of two mathematical models.

Early afterdepolarization (EAD) is known as a cause of ventricular arrhythmias in long QT syndromes. We theoretically investigated how the rapid (IKr) and slow (IKs) components of delayed-rectifier K+ channel currents, L-type Ca2+ channel current (ICaL), Na+/Ca2+ exchanger current (INCX), Na+-K+ pump current (INaK), intracellular Ca2+ (Cai) handling via sarcoplasmic reticulum (SR), and intracellular Na+ concentration (Nai) contribute to initiation, termination, and modulation of phase-2 EADs, using two human ventricular myocyte models. Bifurcation structures of dynamical behaviors in model cells were explored by calculating equilibrium points, limit cycles (LCs), and bifurcation points as functions of parameters. EADs were reproduced by numerical simulations. The results are summarized as follows: 1) decreasing IKs and/or IKr or increasing ICaL led to EAD generation, to which mid-myocardial cell models were especially susceptible; the parameter regions of EADs overlapped the regions of stable LCs. 2) Two types of EADs (termination mechanisms), IKs activation-dependent and ICaL inactivation-dependent EADs, were detected; IKs was not necessarily required for EAD formation. 3) Inhibiting INCX suppressed EADs via facilitating Ca2+-dependent ICaL inactivation. 4) Cai dynamics (SR Ca2+ handling) and Nai strongly affected bifurcations and EAD generation in model cells via modulating ICaL, INCX, and INaK Parameter regions of EADs, often overlapping those of stable LCs, shifted depending on Cai and Nai in stationary and dynamic states. 5) Bradycardia-related induction of EADs was mainly due to decreases in Nai at lower pacing rates. This study demonstrates that bifurcation analysis allows us to understand the dynamical mechanisms of EAD formation more profoundly. NEW & NOTEWORTHY: We investigated mechanisms of phase-2 early afterdepolarization (EAD) by bifurcation analyses of human ventricular myocyte (HVM) models. EAD formation in paced HVMs basically depended on bifurcation phenomena in non-paced HVMs, but was strongly affected by intracellular ion concentrations in stationary and dynamic states. EAD generation did not necessarily require IKs.

Intragastric injection of Lactobacillus casei strain Shirota suppressed spleen sympathetic activation by central corticotrophin-releasing factor or peripheral 2-deoxy-d-glucose in anesthetized rats.

Intragastric (IG) administration of probiotic strain Lactobacillus casei Shirota (LcS) decreases the sympathetic nerve outflow of anesthetized rats in a tissue-specific manner. In the present study, we examined the effects of IG administration of LcS on sympathetic activation induced by an intracerebroventricular (ICV) injection of corticotrophin-releasing factor (CRF) and an intravenous (IV) injection of 2-deoxy-d-glucose (2DG) or interleukin (IL)-1ß in urethane-anesthetized rats. The IG administration of LcS differently affected the stimulatory responses of sympathetic nerve outflow to CRF. LcS suppressed the increase in splenic sympathetic nerve activity (Spleen-SNA), induced by central CRF, in a dose-dependent manner; however, it did not alter adrenal sympathetic nervous activity (ASNA). In contrast, LcS did not affect spleen-SNA and ASNA following an IV injection of IL-1ß. On the other hand, IG administration of LcS suppressed the activation of ASNA following an IV injection of 2DG. These findings suggest that the suppression of central CRF-induced sympathetic activation by LcS is tissue-specific. Moreover, it can suppress the 2DG-induced sympathetic activation. Furthermore, we found that stomach-specific vagotomy attenuates the suppressive effect of LcS on CRF-mediated spleen-SNA activation. Thus, the present study suggests that LcS administered to the stomach may act on the afferent vagal nerve and send afferent signals to the brain to regulate efferent SNA induced by sympathetic stimulators.

Central Insulin Action Activates Kupffer Cells by Suppressing Hepatic Vagal Activation via the Nicotinic Alpha 7 Acetylcholine Receptor.

Central insulin action activates hepatic IL-6/STAT3 signaling, which suppresses the gene expression of hepatic gluconeogenic enzymes. The vagus nerve plays an important role in this centrally mediated hepatic response; however, the precise mechanism underlying this brain-liver interaction is unclear. Here, we present our findings that the vagus nerve suppresses hepatic IL-6/STAT3 signaling via α7-nicotinic acetylcholine receptors (α7-nAchR) on Kupffer cells, and that central insulin action activates hepatic IL-6/STAT3 signaling by suppressing vagal activity. Indeed, central insulin-mediated hepatic IL-6/STAT3 activation and gluconeogenic gene suppression were impeded in mice with hepatic vagotomy, pharmacological cholinergic blockade, or α7-nAchR deficiency. In high-fat diet-induced obese and insulin-resistant mice, control of the vagus nerve by central insulin action was disturbed, inducing a persistent increase of inflammatory cytokines. These findings suggest that dysregulation of the α7-nAchR-mediated control of Kupffer cells by central insulin action may affect the pathogenesis of chronic hepatic inflammation in obesity.

Simvastatin and atorvastatin facilitates amyloid ß-protein degradation in extracellular spaces by increasing neprilysin secretion from astrocytes through activation of MAPK/Erk1/2 pathways.

One of the major neuropathological hallmarks of Alzheimer's disease (AD) is the deposition of amyloid ß-protein (Aß) in the brain. Aß accumulation seems to arise from an imbalance between Aß production and clearance. Neprilysin (NEP) and insulin-degrading enzyme (IDE) are the important Aß-degrading enzymes in the brain, and deficits in their expression may promote Aß deposition in patients with sporadic late-onset AD. Statins, which are used clinically for reducing cholesterol levels, can exert beneficial effects on AD. Therefore, we examined whether various statins are associated with Aß degradation by inducing NEP and IDE expression, and then evaluating the relation between activation of intracellular signaling transduction, inhibition of cholesterol production, and morphological changes to astrocytes. Treating cultured rat astrocytes with simvastatin and atorvastatin significantly decreased the expression of NEP but not IDE in a concentration- and time-dependent manner. The decrease in NEP expression was a result of activation of extracellular signal-regulated kinase (ERK) but not the reduction of cholesterol synthesis pathway. This NEP reduction was achieved by the release to the extracellular space of cultured astrocytes. Furthermore, the cultured medium prepared from simvastatin- and atorvastatin-treated astrocytes significantly induced the degradation of exogenous Aß. These results suggest that simvastatin and atorvastatin induce the increase of Aß degradation of NEP on the extracellular of astrocytes by inducing ERK-mediated pathway activity and that these reagents regulate the differential mechanisms between the secretion of NEP, the induction of cholesterol reduction, and the morphological changes in the cultured astrocytes.

Possible role of afferent autonomic signals in abdominal organs in anorexic and cardiovascular responses to nicotine injection in rats.

Smoking generally causes an increase in nicotine levels in the blood, affecting the brain components, such as the hypothalamus (feeding-related area) or the brain stem (cardiovascular control area). In terms of nicotine transmission to the brain, a new insight that the afferent vagal nerve in the liver is important for sensing increased nicotine levels in the blood and informing the brain was reported in an experiment with rats. However, it has not been clarified whether the afferent autonomic nerve system is implicated in feeding and cardiovascular responses to nicotine. Here, we examined the possible role of afferent autonomic nerve transmission in rats in regulating feeding behavior and cardiovascular functions by nicotine. An intravenous injection of nicotine dose dependently increased the blood pressure (BP) in urethane-anesthetized rats; high nicotine doses also led to an increase in BP in conscious rats. Further, an intravenous injection of nicotine for 3 days reduced food intake and body weight gain in rats. The weight-reducing action of intravenous nicotine was abolished by blocking the afferent sympathetic signals in the abdominal organs, but not the vagal nerve signals. Moreover, the hypertensive action of nicotine was not abolished either by afferent sympathectomy or by vagotomy. Thus, these data suggest that nicotine injected into the vein acts on the afferent sympathetic nerve in the abdominal organs and transmits signals to the brain for reducing body weight, but not for suppressing appetite or increasing BP.

Leptin inhibits amyloid ß-protein fibrillogenesis by decreasing GM1 gangliosides on the neuronal cell surface through PI3K/Akt/mTOR pathway.

Leptin is a centrally acting hormone that controls metabolic pathways. Recent epidemiological studies suggest that plasma leptin is protective against Alzheimer's disease. However, the mechanism that underlies this effect remains uncertain. To investigate whether leptin inhibits the assembly of amyloid ß-protein (Aß) on the cell surface of neurons, we treated primary neurons with leptin. Leptin treatment decreased the GM1 ganglioside (GM1) levels in the detergent-resistant membrane microdomains (DRMs) of neurons. The increase in GM1 expression induced by leptin was inhibited after pre-treatment with inhibitors of phosphatidylinositol 3-kinase (LY294002), Akt (triciribine) and the mammalian target of rapamycin (i.e. rapamycin), but not by an inhibitor of extracellular signal-regulated kinase (PD98059). In addition, pre-treatment with these reagents blocked the induction of GM1 in DRMs by leptin. Furthermore, Aß assembly on the cell surface of neurons was inhibited greatly after treatment with leptin. This reduction was markedly inhibited after pre-treatment with LY294002, triciribine, and rapamycin. These results suggest that leptin significantly inhibits Aß assembly by decreasing GM1 expression in DRMs of the neuronal surface through the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin pathway. These findings highlight the importance of understanding the function of leptin in AD brains. In this study, our aim was to determine whether leptin regulates the expression and localization of GM1 on the neuronal membrane and if it induces the formation of Aß assembly on the cell surface of neurons. Our results suggest that leptin regulates the expression of GM1 in DRMs of the neuronal membranes. Moreover, leptin does not seem to facilitate fibrillogenesis of exogenously added soluble Aß from the cell surface of neurons.

Leptin inhibits amyloid ß-protein degradation through decrease of neprilysin expression in primary cultured astrocytes.

Pathogenesis of Alzheimer's disease (AD) is characterized by accumulation of extracellular deposits of amyloid ß-protein (Aß) in the brain. The steady state level of Aß in the brain is determined by the balance between its production and removal; the latter occurring through egress across blood and CSF barriers as well as Aß degradation. The major Aß-degrading enzymes in the brain are neprilysin (NEP) and insulin-degrading enzyme (IDE), which may promote Aß deposition in patients with sporadic late-onset AD. Epidemiological studies have suggested an inverse relationship between the adipocytokine leptin levels and the onset of AD. However, the mechanisms underlying the relationship remain uncertain. We investigated whether leptin is associated with Aß degradation by inducing NEP and IDE expression within primary cultured astrocytes. Leptin significantly decreased the expression of NEP but not IDE in a concentration- and time-dependent manner through the activation of extracellular signal-regulated kinase (ERK) in cultured rat astrocytes. Furthermore, leptin inhibited the degradation of exogenous Aß in primary cultured astrocytes. These results suggest that leptin suppresses Aß degradation by NEP through activation of ERK.

PACAP is implicated in the stress axes.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a highly conserved pleiotropic neuropeptide that functions as a neurotransmitter, neuromodulator and neurotrophic factor. Accumulating evidence implicates PACAP as an important regulator of both central and/or peripheral components of the stress axes, particularly exposure to prolonged or traumatic stress. Indeed, PACAP and its cognate receptors are widely expressed in the brain regions and peripheral tissues that mediate stress-related responses. In the sympathoadrenomedullary system, PACAP is required for sustained epinephrine secretion during metabolic stress. It is likely that PACAP regulates autonomic function and contributes to peripheral homeostasis by maintaining a balance between sympathetic and parasympathetic activity, favoring stimulation of the sympathetic system. Furthermore, PACAP is thought to act centrally on the paraventricular nucleus of the hypothalamus to regulate both the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Intriguingly, PACAP is also active in brain structures that mediate anxiety- and fear-related behaviors, and the expression of PACAP and its receptors are dynamically altered under pathologic conditions. Thus PACAP may influence both hard-wired (genetically determined) stress responses and gene-environment interactions in stress-related psychopathology. This article aims to overview the molecular mechanisms and psychiatric implications of PACAP-dependent stress responses.

PACAP centrally mediates emotional stress-induced corticosterone responses in mice.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide widely distributed in the nervous system. Recently, PACAP was shown to be involved in restraint stress-induced corticosterone release and concomitant expression of the genes involved in hypothalamic-pituitary-adrenal (HPA) axis activation. Therefore, in this study, we have addressed the types of stressors and the levels of the HPA axis in which PACAP signaling is involved using mice lacking PACAP (PACAP⁻/⁻). Among four different types of stressors, open-field exposure, cold exposure, ether inhalation, and restraint, the corticosterone response to open-field exposure and restraint, which are categorized as emotional stressors, but not the other two, was markedly attenuated in PACAP⁻/⁻ mice. Peripheral administration of corticotropin releasing factor (CRF) or adrenocorticotropic hormone induced corticosterone increase similarly in PACAP⁻/⁻ and wild-type mice. In addition, the restraint stress-induced c-Fos expression was significantly decreased in the paraventricular nucleus (PVN) and medial amygdala (MeA), but not the medial prefrontal cortex, in PACAP⁻/⁻ mice. In the PVN of PACAP⁻/⁻ mice, the stress-induced c-Fos expression was blunted in the CRF neurons. These results suggest that PACAP is critically involved in activation of the MeA and PVN CRF neurons to centrally regulate the HPA axis response to emotional stressors.

The melanocortin system is involved in regulating autonomic nerve activity through central pituitary adenylate cyclase-activating polypeptide.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a peptidergic neurotransmitter that is highly expressed in the nervous system. We have previously reported that a central injection of PACAP leads to changes in the autonomic nervous system tones including sympathetic excitation and parasympathetic inhibition. An anatomical study revealed that melanocortin and PACAP are colocalized in some hypothalamic nuclei. Here, we investigated the possible role of the melanocortin system in autonomic control by PACAP using SHU9119, an antagonist of the melanocortin receptors (MC3-R/MC4-R). Pretreatment with SHU-9119 did not affect the activating neural responses of adrenal, renal, and lumbar sympathetic nerves following a PACAP injection However, SHU9119 significantly eliminated the suppressing effect of a PACAP injection on gastric vagal nerve activity and excitation effects on liver and brown adipose tissue sympathetic nerve activities. These results suggest that the brain melanocortin system might play a key role in the control of thermogenic sympathetic outflows and digestive parasympathetic outflow by PACAP, but this system does not participate in the central effects of PACAP on cardiovascular function and neural activities of renal, adrenal, and lumbar sympathetic nerves.

Regulation of autonomic nerve activities by central pituitary adenylate cyclase-activating polypeptide.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a peptidergic neurotransmitter that is expressed in high levels in nervous systems. Here, we investigated the roles of PACAP in autonomic system regulation by evaluating the changes caused in the autonomic nerve activities after injecting PACAP into the central nervous system (CNS) and examining stress-induced blood glucose changes in PACAP-deficient (PACAP-/-) mice. Renal sympathetic nerve activity (RSNA), blood pressure, and heart rate were elevated after injecting PACAP into the third cerebral ventricle (3CV). Similarly, other sympathetic nerve activities, including adrenal sympathetic nerve activity (ASNA), celiac sympathetic nerve activity (CSNA), and brown adipose tissue sympathetic nerve activity (BAT-SNA), were accelerated by PACAP injection. In contrast, injecting PACAP into 3CV significantly suppressed parasympathetic nerve activities, including gastric vagal nerve activity (GVNA) and celiac vagal nerve activity (CVNA). In addition, blood glucose elevations induced by stress, such as immobilization or ether exposure, were disrupted in PACAP-/- mice, although basal glucose levels in mutants were comparable to that in wild-type mice. These results suggest that CNS PACAP regulates autonomic function by maintaining a sympathetic-parasympathetic balance and contributes to peripheral homeostatic maintenance, especially under conditions of stress.

Depression-like behavior in the forced swimming test in PACAP-deficient mice: amelioration by the atypical antipsychotic risperidone.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide with pleiotropic functions. We report here that PACAP-deficient (PACAP-/-) mice showed increased immobility in a forced swimming test, which was reduced by the antidepressant desipramine, to a similar extent as in wild-type mice. The atypical antipsychotic risperidone and the selective serotonin (5-HT)(2) antagonist ritanserin normalized the depression-like behavior in PACAP-/- mice. The 5-HT(2) agonist (+/-)-2,5-dimethoxy-4-iodoamphetamine-induced 5-HT syndrome was exaggerated in PACAP-/- mice, which suggests a 5-HT(2)-receptor-dependent mechanism in the depression-like behavior. The circadian rhythm of plasma corticosterone and body core temperature was significantly flattened in the mutants. mRNA expression of glucocorticoid receptor was reduced in the mutant hippocampus. The present results suggest that alterations in PACAP signaling might contribute to the pathogenesis of certain depressive conditions amenable to atypical antipsychotic drugs.

Effect of the culture extract of Lentinus edodes mycelia on splenic sympathetic activity and cancer cell proliferation.

The spleen is an important organ for tumor immunity, and the splenic sympathetic nerve has a suppressive effect on splenic natural killer (NK) cytotoxicity. On the basis of this and reports that Lentinus edodes (Shiitake mushroom) has tumor-inhibitory effects, the authors hypothesized that an extract of a mycelial culture of L. edodes grown in a solid medium of sugar-cane bagasse and defatted rice bran-L.E.M-might affect the sympathetic splenic sympathetic nerve activity (Splenic-SNA) and thus inhibit tumor proliferation. Thus, the effect of L.E.M on Splenic-SNA and human cancer cell proliferation was examined. Splenic-SNA was found to be suppressed by an intraduodenal L.E.M injection in urethane-anesthetized rats, which significantly inhibited increases in the tumor volume of human colon and breast cancer cells implanted in athymic nude mice. These findings suggest that L.E.M has an inhibitory effect on tumor proliferation possibly via a reduction in NK cytotoxicity through the suppression of Splenic-SNA.

Lack of light-induced elevation of renal sympathetic nerve activity and plasma corticosterone levels in PACAP-deficient mice.

PACAP is a neurotransmitter involved in the signal transduction of light stimulation in the suprachiasmatic nucleus (SCN). Light stimulation affects autonomic nerve activity via the SCN, and here we tested whether PACAP participates in light-induced regulation of sympatho-adrenal activity by using PACAP-deficient (Adcyap1(-/-)) mice. Light stimulation (100 lux, 30 min) significantly elevated both renal sympathetic nerve activity (RSNA), which was monitored on a digital oscilloscope, and plasma corticosterone levels in wild-type mice, but both responses were almost abolished in Adcyap1(-/-) mice. Although light-induced c-Fos expression in the SCN was observed in both genotypes, the numbers of c-Fos positive cells were significantly decreased in Adcyap1(-/-) mice. These data suggest that PACAP signaling pathway is involved in light-induced stimulation of RSNA and plasma corticosterone release through SCN of brain.

Effects of olfactory stimulations with scents of grapefruit and lavender oils on renal sympathetic nerve and blood pressure in Clock mutant mice.

Previously, we observed that in mice, olfactory stimulation with scent of grapefruit oil elevates renal sympathetic nerve activity and blood pressure. In contrast, olfactory stimulation with scent of lavender oil has opposite effects in mice. Moreover, electrolytic lesions of the mouse hypothalamic suprachiasmatic nucleus eliminated changes in renal sympathetic nerve activity and blood pressure induced by either scent of grapefruit oil or scent of lavender oil. Here, we show that grapefruit oil-induced elevations in renal sympathetic nerve activity and blood pressure were not observed in Clock mutant mice, which harbor mutations in Clock and lack normal circadian rhythms, whereas lavender oil-suppressions were preserved in Clock mutant mice. In addition, responses of c-Fos inductions in the suprachiasmatic nucleus and paraventricular nucleus of the hypothalamus to scent of grapefruit oil observed in wild-type mice were not observed in Clock mutant mice. These findings suggest that the Clock gene might be implicated in elevating responses of autonomic and cardiovascular functions to olfactory stimulation with scent of grapefruit oil.