Characterization of LysoTracker Red uptake by in vitro model cells of the outer blood-retinal barrier: Implication of lysosomal trapping with cytoplasmic vacuolation and cytotoxicity.

Lysosomal trapping, a physicochemical process in which lipophilic cationic compounds are sequestered in lysosomes, can affect drug disposition and cytotoxicity. To better understand lysosomal trapping at the outer blood-retinal barrier (BRB), we investigated the distribution of LysoTracker Red (LTR), a probe compound for lysosomal trapping, in conditionally immortalized rat retinal pigment epithelial (RPE-J) cells. LTR uptake by RPE-J cells was dependent on temperature and attenuated by ammonium chloride and protonophore, which decreased the pH gradient between the lysosome and cytoplasm, suggesting lysosomal trapping of LTR in RPE-J cells. The involvement of lysosomal trapping in response to cationic drugs, including neuroprotectants such as desipramine and memantine, was also suggested by an inhibition study of LTR uptake. Chloroquine, which is known to show ocular toxicity, induced cytoplasmic vacuolization in RPE-J cells with a half-maximal effective concentration of 1.35 µM. This value was 59 times lower than the median lethal concentration (= 79.1 µM) of chloroquine, suggesting that vacuolization was not a direct trigger of cell death. These results are helpful for understanding the lysosomal trapping of cationic drugs, which is associated with drug disposition and cytotoxicity in the outer BRB.

Spatio-temporal categorization for first-person-view videos using a convolutional variational autoencoder and Gaussian processes.

In this study, HcVGH, a method that learns spatio-temporal categories by segmenting first-person-view (FPV) videos captured by mobile robots, is proposed. Humans perceive continuous high-dimensional information by dividing and categorizing it into significant segments. This unsupervised segmentation capability is considered important for mobile robots to learn spatial knowledge. The proposed HcVGH combines a convolutional variational autoencoder (cVAE) with HVGH, a past method, which follows the hierarchical Dirichlet process-variational autoencoder-Gaussian process-hidden semi-Markov model comprising deep generative and statistical models. In the experiment, FPV videos of an agent were used in a simulated maze environment. FPV videos contain spatial information, and spatial knowledge can be learned by segmenting them. Using the FPV-video dataset, the segmentation performance of the proposed model was compared with previous models: HVGH and hierarchical recurrent state space model. The average segmentation F-measure achieved by HcVGH was 0.77; therefore, HcVGH outperformed the baseline methods. Furthermore, the experimental results showed that the parameters that represent the movability of the maze environment can be learned.

Cesarean section delivery is a risk factor of autism-related behaviors in mice.

Cesarean section (C/S) is one way of delivering babies, and is chosen when mothers or babies are facing problems or life-threatening conditions during pregnancy. Many meta-analyses have suggested an etiological relationship between C/S delivery and autism spectrum disorders (ASDs). However, as a risk factor for ASDs, C/S delivery has not yet been well studied. Because C/S deliveries have been increasing, it is very important to investigate the causal association between C/S and ASDs. Here, using three approaches, we showed experimentally that C/S delivery induced ASD-like traits in offspring mice, and that some of these changes were ameliorated by one-time oxytocin (OXT) treatment. Treatment with OXT receptor antagonists before natural delivery also induced ASD-related behaviors. Moreover, wild-type mice born to OXT-KO dams showed similar changes. Thus, insufficient OXT exposure from dams to offspring during delivery may be a trigger for ASD-related behaviors.

HVGH: Unsupervised Segmentation for High-Dimensional Time Series Using Deep Neural Compression and Statistical Generative Model.

Humans perceive continuous high-dimensional information by dividing it into meaningful segments, such as words and units of motion. We believe that such unsupervised segmentation is also important for robots to learn topics such as language and motion. To this end, we previously proposed a hierarchical Dirichlet process-Gaussian process-hidden semi-Markov model (HDP-GP-HSMM). However, an important drawback of this model is that it cannot divide high-dimensional time-series data. Furthermore, low-dimensional features must be extracted in advance. Segmentation largely depends on the design of features, and it is difficult to design effective features, especially in the case of high-dimensional data. To overcome this problem, this study proposes a hierarchical Dirichlet process-variational autoencoder-Gaussian process-hidden semi-Markov model (HVGH). The parameters of the proposed HVGH are estimated through a mutual learning loop of the variational autoencoder and our previously proposed HDP-GP-HSMM. Hence, HVGH can extract features from high-dimensional time-series data while simultaneously dividing it into segments in an unsupervised manner. In an experiment, we used various motion-capture data to demonstrate that our proposed model estimates the correct number of classes and more accurate segments than baseline methods. Moreover, we show that the proposed method can learn latent space suitable for segmentation.

Critical roles of serotonin-oxytocin interaction during the neonatal period in social behavior in 15q dup mice with autistic traits.

Disturbance of neurotransmitters and neuromodulators is thought to underlie the pathophysiology of autism spectrum disorder (ASD). Studies of 15q dup mouse models of ASD with human 15q11-13 duplication have revealed that restoring serotonin (5-HT) levels can partially reverse ASD-related symptoms in adults. However, it remains unclear how serotonin contributes to the behavioral symptoms of ASD. In contrast, oxytocin (OXT) has been found to involve social and affiliative behaviors. In this study, we examined whether serotonin-OXT interaction during the early postnatal period plays a critical role in the restoration of social abnormality in 15q dup mice. OXT or the 5-HT1A receptor agonist 8OH-DPAT treatment from postnatal day 7 (PD7) to PD21 ameliorated social abnormality in the three-chamber social interaction test in adult 15q dup mice. The effect of 8OH-DPAT was inhibited by blockade of OXT receptors in 15q dup mice. Thus, serotonin-OXT interaction via 5-HT1A receptors plays a critical role in the normal development of social behavior in 15q dup mice. Therefore, targeting serotonin-OXT interaction may provide a novel therapeutic strategy for treatment of ASD.

Developmental Changes in Serotonergic Modulation of GABAergic Synaptic Transmission and Postsynaptic GABAA Receptor Composition in the Cerebellar Nuclei.

Outputs from the cerebellar nuclei (CN) are important for generating and controlling movement. The activity of CN neurons is controlled not only by excitatory inputs from mossy and climbing fibers and by γ-aminobutyric acid (GABA)-based inhibitory transmission from Purkinje cells in the cerebellar cortex but is also modulated by inputs from other brain regions, including serotonergic fibers that originate in the dorsal raphe nuclei. We examined the modulatory effects of serotonin (5-HT) on GABAergic synapses during development, using rat cerebellar slices. As previously reported, 5-HT presynaptically decreased the amplitudes of stimulation-evoked inhibitory postsynaptic currents (IPSCs) in CN neurons, with this effect being stronger in slices from younger animals (postnatal days [P] 11-13) than in slices from older animals (P19-21). GABA release probabilities accordingly exhibited significant decreases from P11-13 to P19-21. Although there was a strong correlation between the GABA release probability and the magnitude of 5-HT-induced inhibition, manipulating the release probability by changing extracellular Ca2+ concentrations failed to control the extent of 5-HT-induced inhibition. We also found that the IPSCs exhibited slower kinetics at P11-13 than at P19-21. Pharmacological and molecular biological tests revealed that IPSC kinetics were largely determined by the prevalence of α1 subunits within GABAA receptors. In summary, pre- and postsynaptic developmental changes in serotonergic modulation and GABAergic synaptic transmission occur during the second to third postnatal weeks and may significantly contribute to the formation of normal adult cerebellar function.

Differential effects of neonatal SSRI treatments on hypoxia-induced behavioral changes in male and female offspring.

Prenatal hypoxia induced by transient intrauterine ischemia is a serious clinical problem, and at present, effective treatments are lacking. Currently, it is unknown how prenatal hypoxia affects behaviors in adulthood. Therefore, we developed a mouse model that mimics prenatal hypoxia in humans using uterine artery occlusion in late gestation. We examined whether prenatal hypoxia induces behavioral changes in adult male and female offspring by conducting a series of behavioral tests. In adulthood, longer immobility was observed in the forced swim test in males, whereas females showed decreased inhibition in the prepulse inhibition test. We then investigated the effects of two different selective serotonin reuptake inhibitors (SSRIs), fluoxetine (FLX) and escitalopram (ESC), on these behavioral changes. These drugs affect the neurodevelopmental process and have long-term neurological consequences. FLX treatment from postnatal day 3 (P3) to P21 ameliorated the behavioral changes in both male and female mice. In comparison, ESC treatment ameliorated the behavioral changes only in female mice. Neurochemical analysis revealed that dopamine was increased in the female hippocampus, but not in males. Thus, neonatal SSRI treatment decreases dopamine levels in the hippocampus in females selectively. Our findings suggest that prenatal hypoxia is a risk factor for behavioral abnormalities in adulthood, and that neonatal SSRI treatment might have clinical potential for alleviating these long-term behavioral deficits.

Serotonin rebalances cortical tuning and behavior linked to autism symptoms in 15q11-13 CNV mice.

Serotonin is a critical modulator of cortical function, and its metabolism is defective in autism spectrum disorder (ASD) brain. How serotonin metabolism regulates cortical physiology and contributes to the pathological and behavioral symptoms of ASD remains unknown. We show that normal serotonin levels are essential for the maintenance of neocortical excitation/inhibition balance, correct sensory stimulus tuning, and social behavior. Conversely, low serotonin levels in 15q dup mice (a model for ASD with the human 15q11-13 duplication) result in impairment of the same phenotypes. Restoration of normal serotonin levels in 15q dup mice revealed the reversibility of a subset of ASD-related symptoms in the adult. These findings suggest that serotonin may have therapeutic potential for discrete ASD symptoms.

Influence of neonatal sevoflurane exposure on nerve development-related microRNAs and behavior of rats.

Commonly used anesthetics adversely affect the developing brain, but the mechanisms remain unknown. We previously showed that the expressions of microRNAs (miRNAs) in major organs are affected by anesthetics. Therefore, we used TaqMan low-density array (TLDA) to analyze gene expression in the hippocampus of neonatal rats exposed to sevoflurane and performed behavioral tests after they reached adulthood to evaluate cognitive and memory function. Rat male pups at postnatal day 7 were exposed to 1.9% sevoflurane for 3 h, and the hippocampus-miRNA expression profile on postnatal day 8 was determined. Open field and fear conditioning tests conducted during postnatal weeks 7 and 8 indicated that sevoflurane-exposed rats, but not controls, exhibited anxiety-like disorders. TLDA analysis identified 20 differentially expressed miRNAs, which were not shared between postnatally and maturely sevoflurane-exposed rats. The level of rno-miR-632, which targets brain-derived neurotrophic factor and calcium channel, voltage-dependent, alpha 2/delta subunit 2, increased by 10-fold, indicating that exposure to sevoflurane during early neural development alters hippocampus-miRNA expression and may induce subsequent behavioral disorders.

Redox regulation of mammalian 3-mercaptopyruvate sulfurtransferase.

A cystine-catabolizing enzyme, 3-mercaptopyruvate sulfurtransferase catalyzes the trans-sulfuration reaction of mercaptopyruvate or thiosulfate to thiol-containing compounds or cyanide. During the catalytic process, persulfide is formed at the catalytic site cysteine residue and a sulfur-acceptor substrate donates the outer sulfur of the persulfide to form a new persulfide molecule. Subsequently, the molecule can be reduced by thioredoxin to form hydrogen sulfide. The enzyme is regulated by redox changes via two redox-sensing molecular switches consisting redox-sensitive cysteine residues. One switch is the catalytic cysteine in itself, which is oxidized to form a cysteine-sulfenate resulting in inhibition of catalytic activity. The sulfenate can be reduced by thioredoxin resulting in restoration of the activity. The redox potential of sulfenate is lower than that of glutathione and greater than that of thioredoxin. The other switch involves cysteine residues positioned on the surface of the enzyme. The oxidation the intermolecular disulfide linkage at these cysteine residues, leading to dimer formation, inhibits enzyme activity. On the other hand, reduction-associated monomer formation increases catalytic activity. Thioredoxin reduces the disulfide bond more effectively than dithiothreitol, although the specificity mechanism has not been identified. Congenital defects in this enzyme result in, mercaptolactate-cysteine disulfiduria associated with or without mental retardation. However, the pathogenesis has not been identified. Because 3-mercaptopyruvate sulfurtransferase serves as a cellular antioxidative protein, the other biological functions related to the inhabitant disease are being investigated.

Antioxidant enzyme, 3-mercaptopyruvate sulfurtransferase-knockout mice exhibit increased anxiety-like behaviors: a model for human mercaptolactate-cysteine disulfiduria.

Human mercaptolactate-cysteine disulfiduria (MCDU) was first recognized and reported in 1968. Most cases of MCDU are associated with mental retardation, while the pathogenesis remains unknown. To investigate it, we generated homozygous 3-mercaptopyruvate sulfurtransferase (MST: EC 2.8.1.2) knockout (KO) mice using C57BL/6 embryonic stem cells as an animal model. The MST-KO mice showed significantly increased anxiety-like behaviors with an increase in serotonin level in the prefrontal cortex (PFC), but not with abnormal morphological changes in the brain. MCDU can be caused by loss in the functional diversity of MST; first, MST functions as an antioxidant protein. MST possessing 2 redox-sensing molecular switches maintains cellular redox homeostasis. Second, MST can produce H2S (or HS(-)). Third, MST can also produce SOx. It is concluded that behavioral abnormality in MST-KO mice is caused by MST function defects such as an antioxidant insufficiency or a new transducer, H2S (or HS(-)) and/or SOx deficiency.

Early intervention with fluoxetine reverses abnormalities in the serotonergic system and behavior of rats exposed prenatally to dexamethasone.

Many psychiatric disorders emerge after adolescence. Among a variety of predisposing factors, prenatal stress has been thought to cause the symptoms of anxiety disorders. We recently reported that prenatal dexamethasone (DEX) exposure, which mimics some aspects of prenatal stress, induced anxiety-related behaviors in male offspring when they reached adulthood. Before the emergence of behavioral changes, abnormalities occurred in the hypothalamic-pituitary-adrenal axis during postnatal development. In the present study, we found abnormalities in serotonin (5-HT) signaling, including decreased expression of 5-HT(1A) receptor (5-HT(1A)-R) mRNA in the medial prefrontal cortex (mPFC) and 5-HT content in the hippocampus at postnatal week (PW) 4. These results support using early therapeutic interventions with serotonergic drugs to prevent late-emerging anxiety symptoms. To test this hypothesis, we treated rat pups born to DEX-administered mothers with fluoxetine (FLX), a selective serotonin reuptake inhibitor commonly used as an anti-anxiety medication, via breast milk from postnatal day (PD) 2-21. Anxiety-related behaviors examined at PW11-13 were not observed in the prenatally DEX-exposed offspring that were treated with FLX. Likewise, FLX increased 5-HT concentrations in the mPFC and ventral hippocampus at PW3 and normalized 5-HT(1A)-R mRNA concentrations in the mPFC at PW4. The decrease in brain-derived neurotrophic factor (BDNF) protein in the mPFC and dorsal hippocampus was also restored at PW4. Furthermore, administration of the 5-HT(1A)-R full agonist (R)-(+)-8-hydroxy-2-(di-n-propylamino)tetralin from PD2 to 21 also prevented the emergence of behavioral abnormalities in the prenatally DEX-exposed offspring, implicating the involvement of 5-HT(1A)-Rs in the neonatal FLX effect. Collectively, an early pharmacological intervention to normalize serotonergic transmission effectively suppressed the emergence of symptoms induced by prenatal DEX exposure in rats.

Distribution and pharmacological characterization of primate NK-2 tachykinin receptor in the central nervous system of the rhesus monkey.

Tachykinin NK-2 receptor, a cognate receptor for neurokinin A, expressed in the brain has been suggested as a new target for the treatment of psychiatric disorders. In rodents, treatment with NK-2 receptor agonists causes anxiogenic effects, while NK-2 receptor antagonists show anxiolytic and antidepressant-like effects. However, information about the distribution and functions of NK-2 receptors in the central nervous system (CNS) in primates is still lacking. Here, we examined the distribution and pharmacological profile of NK-2 receptors in the rhesus monkey (Macaca mulatta) to clarify the molecular basis of NK-2-mediated tachykininergic functions in the primate CNS. NK-2 receptors cloned from the rhesus monkey brain showed similar pharmacological properties to those of human NK-2 receptors. Substantial expression levels of NK-2 mRNA were observed in all the brain regions examined, including areas pertinent to the emotional networks such as the prefrontal cortex, cingulate cortex and amygdala. These findings suggest that NK-2 receptors may play important roles in the pathophysiology of psychiatric disorders.

Effects of stress memory by fear conditioning on nerve-mast cell circuit in skin.

Inflammatory skin disorder aggravates when a horrific memory is evoked, but the mechanism of this effect is unclear. The objective of the present study was to examine the effects of evocation of a horrific memory on the skin and mast cells in an animal model. A sound stimulus linked to an electric shock was given to C57BL/6 mice (7-week old, males). One, 3 and 5 days later, the mice received the sound stimulus again. The reactions of mice that received the initial sound stimulus were compared with those of mice that did not receive the initial stimulus. A freezing phenomenon was observed when the sound stimulus was given to mice that received the initial stimulus, which indicated evocation of a past memory of fear. The degranulation rate of dermal mast cells and the length of substance P (SP)-positive nerve fibers of the skin significantly increased on days 1 and 3, the SP level decreased significantly, and the number of SP-expressing cells in the dorsal root ganglion significantly increased on day 1. These findings suggest that prior experience of severe stress linked to a stimulus subsequently evokes fear associated with the same stimulus and results in activation of dermal mast cells and skin nerves.

Chronic stress enhances synaptic plasticity due to disinhibition in the anterior cingulate cortex and induces hyper-locomotion in mice.

The anterior cingulate cortex (ACC) is involved in the pathophysiology of a variety of mental disorders, many of which are exacerbated by stress. There are few studies, however, of stress-induced modification of synaptic function in the ACC that is relevant to emotional behavior. We investigated the effects of chronic restraint stress (CRS) on behavior and synaptic function in layers II/III of the ACC in mice. The duration of field excitatory postsynaptic potentials (fEPSPs) was longer in CRS mice than in control mice. The frequency of miniature inhibitory postsynaptic currents (mIPSCs) recorded by whole-cell patch-clamping was reduced in CRS mice, while miniature excitatory postsynaptic currents (mEPSCs) remained unchanged. Paired-pulse ratios (PPRs) of the fEPSP and evoked EPSC were larger in CRS. There was no difference in NMDA component of evoked EPSCs between the groups. Both long-term potentiation (LTP) and long-term depression of fEPSP were larger in CRS mice than in control mice. The differences between the groups in fEPSP duration, PPRs and LTP level were not observed when the GABA(A) receptor was blocked by bicuculline. Compared to control mice, CRS mice exhibited hyper-locomotive activity in an open field test, while no difference was observed between the groups in anxiety-like behavior in a light/dark choice test. CRS mice displayed decreased freezing behavior in fear conditioning tests compared to control mice. These findings suggest that CRS facilitates synaptic plasticity in the ACC via increased excitability due to disinhibition of GABA(A) receptor signalling, which may underlie induction of behavioral hyper-locomotive activity after CRS.

Prenatal dexamethasone exposure affects anxiety-like behaviour and neuroendocrine systems in an age-dependent manner.

Prenatal stress has been reported to alter the development of the central nervous system functions. This alteration is thought to be partly caused by increased fetal exposure to glucocorticoid. To clarify how prenatal stress affects neuroendocrine systems and behaviour in an age-dependent manner, we administered a synthetic glucocorticoid, dexamethasone, as a stressor to pregnant rats at gestational days 16-21 and examined the developmental changes in behaviour, hypothalamic corticotropin-releasing factor mRNA expression, corticosterone response and glucocorticoid receptor expression in male offspring. Prenatal dexamethasone exposure decreased corticotropin-releasing factor mRNA in the hypothalamus and disturbed the plasma corticosterone response to restraint stress in the offspring at postnatal week 4 (PW4). In contrast, it was not until PW10 that increased anxiety-like behaviour emerged in the dexamethasone-exposed offspring. In association with the acquisition of increased anxiety-like behaviour at PW10, glucocorticoid receptor expression was decreased in the amygdala in dexamethasone-exposed offspring at PW7 and PW10. Thus, our longitudinal analysis suggests that prenatal exposure to glucocorticoid hampers neuroendocrinological development in the offspring during early life, and that this disturbance results in the induction of increased anxiety-like behaviour in adulthood.

Low serum levels of brain-derived neurotrophic factor and epidermal growth factor in patients with chronic schizophrenia.

Neurotrophic factors (NFs) play a pivotal role in the development of the central nervous system. They are thus also suspected of being involved in the etiology of schizophrenia. Previous studies reported a decreased level of serum brain-derived neurotrophic factor (BDNF) in schizophrenia, whereas the association of epidermal growth factor (EGF) with this illness remains controversial. Using a two-site enzyme immunoassay, we conducted the simultaneous measurement of serum BDNF and EGF levels in a group of patients with chronic schizophrenia (N=74) and a group of normal controls matched in age, body mass index, smoking habit and sex (N=87). We found that, compared to normal controls, patients with chronic schizophrenia exhibited lower serum levels of both BDNF and EGF across all ages examined (21-59 years). The serum levels of BDNF and EGF were negatively correlated in the controls (r=-0.387, P=0.0002) but not in the patients. Clinical parameters such as duration of illness and psychiatric rating scale also showed no robust correlations with the NF levels. Collectively, these results suggest that pervasive, abnormal signaling of NFs underlies the pathophysiology of chronic schizophrenia.

Dynamic changes in nerve growth factor and substance P in the murine hair cycle induced by depilation.

Increasing evidence suggests that various neurotrophins and neuropeptides play an important role in the progression of hair follicle cycling. Among them, nerve growth factor (NGF) and substance P (SP) have attracted special interest recently. However, the interaction between these factors during hair cycling has not yet been systematically studied. We therefore investigated the mutual relationships between NGF and SP and the mechanism by which the anagen stage of the hair cycle is initiated. Fluctuations in numbers of SP-positive nerve fibers and variations in amounts of SP, NGF, and another neurotrophic factor, glial cell-derived neurotrophic factor, in skin in the C57BL/6 mouse depilation-induced hair cycle model, together with the spatiotemporal expression patterns of each of these factors, were followed simultaneously by enzyme-linked immunosorbent assay and immunohistochemistry. The main finding was that a surge in NGF expression and a rapid increase in NGF content in skin is an initial event within 1 day after depilation, followed by elevation of SP content and numbers of SP-containing fibers 2 days after the increase in NGF. Our findings suggest that a rapid and abundant increase in NGF plays a key role in the induction and progression of anagen hair cycling through keratinocyte growth promotion. NGF may also induce plastic changes such as sprouting and hyperplasia in dermal nerve fibers and enhance their SP production. Elevated levels of SP in skin may additionally contribute to the progression of consecutive anagen hair cycles.

Expression changes of cation chloride cotransporters in the rat spinal cord following intraplantar formalin.

Cation chloride cotransporters, K(+)-Cl(-) cotransporter 2 (KCC2) and Na(+)-K(+)-Cl(-) cotransporter 1 (NKCC1) are reported to be expressed in the neurons in the spinal cord and regulate intracellular Cl(-) concentration. Evidence has been accumulating that the expression of cation chloride cotransporters changes in inflammatory or neuropathic pain, and such changes take a part in pathophysiology of the persistent pain states. However, it is largely unknown how these cotransporters contribute to hyperalgesia in the acute pain state. We, therefore, investigated expression changes of KCC2 and NKCC1 in the spinal dorsal horn of the rat after the intraplantar injection of formalin as an acute nociceptive stimulus. The rats showed two phases (phases 1 and 2) of increase in pain-related behavior in response to formalin. We found that expression of KCC2-like immunoreactivity (IR) was reduced in lamina I and II in the lumbar spinal cord on the stimulated side in phase 1, and then recovered gradually. In contrast, the number of NKCC1-like IR-positive cells was unchanged over the period examined. These results suggest that KCC2, rather than NKCC1, mainly contributes to modulating excitability of the dorsal spinal cord neurons in the initial stage of formalin-evoked hyperalgesia.

Role of substance P in stress-derived degranulation of dermal mast cells in mice.

BACKGROUND: The interaction between nerves and mast cells can effect regulation of the immune system and inflammatory responses. Recent studies have shown that various stressors can induce degranulation of dermal mast cells in animals. OBJECTIVES: This study was conducted to confirm that substance P (SP) was involved in the degranulation of dermal mast cells in stress conditions. METHODS: Using a communication box system, foot shock stress (FS) and psychological stress (PS) were administered to mice and the degranulation rate of dermal mast cells, the number of SP-positive nerve fibers and changes in SP content were determined. The inhibitory effect of a non-peptide NK1-receptor antagonist on these changes was investigated. RESULTS: Both FS and PS significantly enhanced the degranulation of dermal mast cells and increased the number of SP-positive nerve fibers. FS significantly decreased dermal SP content whereas SP was increased by PS. These changes were inhibited by intraperitoneal injection of NK(1) receptor antagonist. CONCLUSIONS: It was considered that SP released from the nerve ending, had an important role in the degranulation of dermal mast cells. Results of this study suggest that the tachykinin receptor antagonist exhibited an inhibitory effect on aggravated stress-induced dermatitis.