No abstract available.
Animals ; Cerebral Cortex* ; Glutamic Acid* ; Glycine* ; Kynurenic Acid* ; Perfusion* ; Rats*

To investigate the mechanism of the excitatory signal transmission, the effects of N-methyl-D-aspartate(NMDA, ionotropic glutamate agonist) and kynurenic acid(glutamate antagonist) on catfish retinal neurons were explored using conventional intracellular recording techniques. Horizontal cells were depolarized by glutamate, kainate, quisqualate, and NMDA but gyperpolarized by kynurenate. Transient components of both ON-and OFF-bipolar cells were reduced either by glutamate or by NMDA. Kynurenate suppressed sustained components of the third-order neurons or OFF-bipolar cells. Furthermore, kynurenate blocked the depolarizing actions of NMDA on horizontal cells and ON-sustained cells with large ON-transient components. The results suggest that NMDA would exert a tonic depolarization in the horizontal cells and the 3rd-order neurons, and there might be a preferential suppression on the a NMDA receptors by kynurenic acid in the catfish retina.
Catfishes ; Glutamic Acid ; Kainic Acid ; Kynurenic Acid* ; N-Methylaspartate ; Neurons* ; Quisqualic Acid ; Receptors, N-Methyl-D-Aspartate ; Retina* ; Retinal Neurons

The basic mechanism for the excitation of the peripheral vestibular receptors following acute hypotension induced by sodium nitroprusside (SNP) or hemorrhage was investigated in anesthetized rats. Electrical activity of the afferent vestibular nerve was measured after pretreatment with kynurenic acid, an NMDA receptor antagonist. The activity of the vestibular nerve at rest following acute hypotension induced by SNP or simulating hemorrhage was a greater increase than in control animals. The gain of the vestibular nerve with sinusoidal rotation following acute hypotension increased significantly compared to control animals. The acute hypotension induced by SNP or hemorrhage did not change the activity of the afferent vestibular nerve after kynurenic acid injection. These results suggest that acute hypotension produced excitation of the vestibular hair cells via glutamate excitotoxicity in response to ischemia.
Animals ; Glutamic Acid ; Hair Cells, Vestibular ; Hemorrhage ; Hypotension* ; Ischemia ; Kynurenic Acid ; N-Methylaspartate ; Nitroprusside ; Rats* ; Vestibular Nerve*

Tryptophan metabolites regulate a variety of physiological processes, and their downstream metabolites enter the kynurenine pathway. Age-related changes of metabolites and activities of associated enzymes in this pathway are suggestable and would be potential intervention targets. Blood levels of serum tryptophan metabolites in C57BL/6 mice of different ages, ranging from 6 weeks to 10 months, were assessed using high-performance liquid chromatography, and the enzyme activities for each metabolic step were estimated using the ratio of appropriate metabolite levels. Mice were subjected to voluntary chronic aerobic exercise or high-fat diet to assess their ability to rescue age-related alterations in the kynurenine pathway. The ratio of serum kynurenic acid (KYNA) to 3-hydroxylkynurenine (3-HK) decreased with advancing age. Voluntary chronic aerobic exercise and high-fat diet rescued the decreased KYNA/3-HK ratio in the 6-month-old and 8-month-old mice groups. Tryptophan metabolites and their associated enzyme activities were significantly altered during aging, and the KYNA/3-HK ratio was a meaningful indicator of aging. Exercise and high-fat diet could potentially recover the reduction of the KYNA/3-HK ratio in the elderly.
Aged ; Aging ; Animals ; Chromatography, Liquid ; Diet, High-Fat* ; Exercise* ; Humans ; Infant ; Kynurenic Acid ; Kynurenine* ; Mice ; Physiological Processes ; Tryptophan*

The decrease in maternal plasma total (free + albumin-bound) tryptophan (Trp) during the third pregnancy trimester is attributed to induction of indoleamine 2,3-dioxygenase (IDO). When measured, free [Trp] is increased because of albumin depletion and non-esterified fatty acid elevation. The Trp depletion concept in pregnancy is therefore not supported because of incorrect interpretation of changes in Trp disposition and also for not addressing mouse strain differences in Trp-related responses and potential inhibition of Trp transport by the IDO inhibitor 1-methyl tryptophan. Application of the Trp utilization concept in pregnancy offers several physiological advantages favoring fetal development and successful outcome, namely provision of Trp for fetal protein synthesis and growth, serotonin for signaling pathways, kynurenic acid for neuroprotection, quinolinic acid for NAD+ synthesis, and other kynurenines for suppression of T cell responses. An excessive increase in Trp availability could compromise pregnancy by undermining T cell suppression, e.g., in pre-eclampsia.
Animals ; Female ; Fetal Development ; Humans ; Indoleamine-Pyrrole 2,3,-Dioxygenase ; Kynurenic Acid ; Mice ; Plasma ; Pre-Eclampsia ; Pregnancy Trimester, Third ; Pregnancy* ; Quinolinic Acid ; Serotonin ; Tryptophan*

To explore the correlation between kynurenine (KYN) metabolites and postpartum depression (PPD), and to provide new possible explanation for the pathogenesis of postpartum depression (PPD).
 Methods: A total of 726 Chinese women, who received cesarean section, were enrolled in this study. PPD was diagnosed with an Edinburgh Postnatal Depression Scale (EPDS) score ≥13. Twenty-four women with PPD and 48 matched women without PPD were randomly selected. The perinatal serum concentrations of KYN, quinolinic acid (QUIN) and kynurenic acid (KYNA) were measured. Subsequently, the puerperants were compared for the differences in the serum concentrations of KYN, QUIN and KYNA at the end of term, day 1 and day 3 after cesarean section, respectively.
 Results: The incidence of PPD was 7.99%. Of clinical characteristics, pressure during pregnancy was significantly different between subjects with or without PPD (P<0.01). Patients with PPD showed significantly increased serum KYN concentration (P<0.05) at the end of term, increased serum QUIN concentration (P<0.05) and decreased KYNA concentration (P<0.05) on the third day after cesarean section as compared with the control women. Furthermore, the KYNA/QUIN ratio was significantly higher in patients with PPD as compared to the control women on the third day after cesarean section (P<0.01).
 Conclusion: The contribution of alterations in plasma levels of KYN, QUIN and KYNA is closely related with the incidence of PPD, and correction of KYNA/QUIN ratio could be a new strategy for the prevention and treatment of postpartum depressive symptoms.
Biomarkers ; blood ; Cesarean Section ; psychology ; China ; epidemiology ; Depression, Postpartum ; blood ; epidemiology ; Female ; Humans ; Incidence ; Kynurenic Acid ; blood ; Kynurenine ; blood ; Pregnancy ; Quinolinic Acid ; blood

Accumulating evidence has suggested the existence of reciprocal communication between immune, endocrine, and neurotransmitter system. Cytokine hypothesis of depression implies that increased pro-inflammatory cytokine such as -1, IL-6, IL-12, TNF-alpha, and IFN-gamma in major depression, acting neuromodulators, play a key role in the mediation of behavioral, neuroendocrine, and neurochemical disturbances in depression. Concerning the relation between cytokines and serotonin metabolism, pro-inflammatory cytokines have profound effects on the metabolism of brain serotonin through the enzyme indoleamine-2,3-dioxygenase(IDO) that metabolizes tryptophan, the precursor of 5-HT to neurodegenerative quinolinate and neuroprotective kynurenate. The neurodegeneration process is reinforced by the neurotoxic effect of the hypercortisolemia during depression. From this perspective, it is possible that efficacy of antidepressants in the treatment of depression may, at least in part, rely on downregulation of pro-inflammatory cytokine synthesis. So, the use of cytokine synthesis inhibitors or cytokine antagonists may be a new treatment approach in depression. However, at present the question whether cytokines play a causal role in the onset of depression or are mere epiphenomena sustaining depressive symptoms remains to be elucidated. Nevertheless, cytokine hypothesis has created new perspectives in the study of psychological and pathophysiological mechanism that are associated with major depression, as well as the prospect for developing a new generation antidepressants.
Antidepressive Agents ; Brain ; Cytokines ; Depression ; Down-Regulation ; Interleukin-12 ; Interleukin-6 ; Kynurenic Acid ; Negotiating ; Neurotransmitter Agents ; Psychoneuroimmunology ; Quinolinic Acid ; Serotonin ; Tryptophan ; Tumor Necrosis Factor-alpha

Retinal prostheses are being developed to restore vision for the blind with retinal diseases such as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). Among the many issues for prosthesis development, stimulation encoding strategy is one of the most essential electrophysiological issues. The more we understand the retinal circuitry how it encodes and processes visual information, the greater it could help decide stimulation encoding strategy for retinal prosthesis. Therefore, we examined how retinal ganglion cells (RGCs) in in-vitro retinal preparation act together to encode a visual scene with multielectrode array (MEA). Simultaneous recording of many RGCs with MEA showed that nearby neurons often fired synchronously, with spike delays mostly within 1 ms range. This synchronized firing - narrow correlation - was blocked by gap junction blocker, heptanol, but not by glutamatergic synapse blocker, kynurenic acid. By tracking down all the RGC pairs which showed narrow correlation, we could harvest 40 functional connectivity maps of RGCs which showed the cell cluster firing together. We suggest that finding functional connectivity map would be useful in stimulation encoding strategy for the retinal prosthesis since stimulating the cluster of RGCs would be more efficient than separately stimulating each individual RGC.
Fires ; Gap Junctions ; Heptanol ; Kynurenic Acid ; Macular Degeneration ; Neurons ; Prostheses and Implants ; Retinal Diseases ; Retinal Ganglion Cells ; Retinaldehyde ; Retinitis Pigmentosa ; Synapses ; Track and Field ; Vision, Ocular ; Visual Prosthesis

BACKGROUND/AIMS: Patients with irritable bowel syndrome (IBS) often report poor sleep quality. Whether poor sleep is associated with tryptophan (Trp) metabolites is unknown. We compared serum Trp metabolites in women with IBS and healthy controls (HCs) using targeted liquid chromatography mass spectrometry (LC-MS)-based profiling. In IBS only, we explored whether Trp metabolites are associated with IBS symptoms and subjective and objective sleep indices, serum cortisol, plasma adrenocorticotropic hormone (ACTH), and cortisol/ACTH levels. METHODS: Blood samples were obtained every 80 minutes in 21 HCs and 38 IBS subjects following an anticipation-of-public-speaking stressor during a sleep laboratory protocol. Subjects completed symptom diaries for 28 days. Adjacent values of metabolites were averaged to represent 4 time-periods: awake, early sleep, mid-sleep, and mid-to-late sleep. Thirteen of 20 targeted Trp metabolites were identified. RESULTS: Ten of 13 Trp metabolites decreased across the night, while nicotinamide increased in both groups. A MANOVA omnibus test performed after principal component analysis showed a significant difference in these 13 principal component (P = 0.014) between groups. Compared to HCs, nicotinamide levels were higher and indole-3-lactic acid levels lower in the IBS group. Melatonin and indole-3-acetic acid levels were associated with several subjective/objective sleep measures; decreased stool consistency/frequency and abdominal pain were positively associated with melatonin and serotonin in the IBS group. The kynurenine and kynurenic acid were associated with ACTH (positively) and cortisol/ACTH (negatively). CONCLUSIONS: Nighttime Trp metabolites may provide clues to poor sleep and stress with IBS. Further study of the mechanism of metabolite action is warranted.
Abdominal Pain ; Adrenocorticotropic Hormone ; Chromatography, Liquid ; Female ; Humans ; Hydrocortisone ; Irritable Bowel Syndrome ; Kynurenic Acid ; Kynurenine ; Mass Spectrometry ; Melatonin ; Niacinamide ; Plasma ; Principal Component Analysis ; Serotonin ; Tryptophan

It has been well documented that transient forebrain global ischemia causes selective neuronal degeneration in hippocampal CA1 pyramidal neurons with a delay of a few days. The mechanism of this delayed hippocampal CA1 pyramidal neuronal death (DND) is still controversial. To delineate the mechanisms of the DND, the effects of treatment with MK-801, an NMDA receptor antagonist, kynurenic acid, a NMDA/non-NMDA receptor antagonist, and/or cycloheximide, a protein synthesis inhibitor, on the DND were investigated in male Wistar rats. To examine the participation of apoptotic neuronal death in the DND, TUNEL staining was performed in ischemic brain section. Global ischemia was induced by 4-vessel occlusion for 20 min. All animals in this study showed the DND 3 and 7 days after the ischemic insult. The DND that occurred 3 days and 7 days after the ischemia were not affected by pretreatment with MK-801 (I mg/kg), but markedly attenuated by the pretreatment with kynurenic acid (500 mg/kg). Treatment with cycloheximide (1 mg/kg) also markedly inhibited the DND. The magnitudes of attenuation by the two drugs were similar. The magnitude of attenuation by co-treatments with kynurenic acid and cycloheximide was not greater than that with any single treatment. TUNEL staining was negative in the sections obtained 1 or 2 days after the ischemic insults, but it was positive at hippocampal CA1 pyramidal cells in sections collected 3 days after the ischemia. These results suggested that the DND should be mediated by the activation of non-NMDA receptor, not by the activation of NMDA receptor and that the activation of AMPA receptor should induce the apoptotic process in the DND.
Animals ; Apoptosis ; Brain* ; Cycloheximide ; Dizocilpine Maleate ; Excitatory Amino Acid Antagonists* ; Glutamic Acid* ; Humans ; In Situ Nick-End Labeling ; Ischemia* ; Kynurenic Acid ; Male ; N-Methylaspartate ; Neurons* ; Prosencephalon ; Pyramidal Cells ; Rats* ; Rats, Wistar ; Receptors, AMPA ; Receptors, Glutamate*