The purpose of this study was to investigate the effect of glutamate and its ionotropic receptor agonists on the response to acute hypoxia in rat carotid body in vitro. Briefly, after SD rats were anesthetized and decapitated, the bilateral carotid bifurcations were rapidly isolated. Then bifurcation was placed into a recording chamber perfused with 95% O₂-5% CO₂ saturated Kreb's solution. The carotid body-sinus nerve complex was dissected, and the carotid sinus nerve discharge was recorded using a suction electrode. To detect the response of carotid body to acute hypoxia, the chamber was perfused with 5% O₂-5% CO₂-90% N₂ saturated Kreb's solution for a period of 100 s at an interval of 15 min. To observe the effect of glutamate, ionotropic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor agonist AMPA or N-methyl-D-aspartate (NMDA) receptor agonist NMDA on the response to acute hypoxia in rat carotid body, the chamber was perfused with 5% O₂-5% CO₂-90% N₂ saturated Kreb's solution containing the corresponding reagent. The results showed that glutamate (20 μmol/L), AMPA (5 μmol/L) or NMDA (10 μmol/L) inhibited the acute hypoxia-induced enhancement of carotid sinus nerve activity, and these inhibitory effects were dose-dependent. In summary, the activation of glutamate ionotropic receptors appears to exert an inhibitory effect on the response to acute hypoxia in carotid body of rats.
Rats ; Animals ; Glutamic Acid/pharmacology* ; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/pharmacology* ; N-Methylaspartate/pharmacology* ; Carotid Body ; Rats, Sprague-Dawley ; Carbon Dioxide ; Receptors, N-Methyl-D-Aspartate ; Receptors, AMPA ; Hypoxia

Experimental autoimmune prostatitis (EAP)-induced persistent inflammatory immune response can significantly upregulate the expression of N-methyl-D-aspartic acid (NMDA) receptors in the paraventricular nucleus (PVN). However, the mechanism has not yet been elucidated. Herein, we screened out the target prostate-derived inflammation cytokines (PDICs) by comparing the inflammatory cytokine levels in peripheral blood and cerebrospinal fluid (CSF) between EAP rats and their controls. After identifying the target PDIC, qualified males in initial copulatory behavior testing (CBT) were subjected to implanting tubes onto bilateral PVN. Next, they were randomly divided into four subgroups (EAP-1, EAP-2, Control-1, and Control-2). After 1-week recovery, EAP-1 rats were microinjected with the target PDIC inhibitor, Control-1 rats were microinjected with the target PDIC, while the EAP-2 and Control-2 subgroups were only treated with the same amount of artificial CSF (aCSF). Results showed that only interleukin-1β(IL-1β) had significantly increased mRNA-expression in the prostate of EAP rats compared to the controls (P < 0.001) and significantly higher protein concentrations in both the serum (P = 0.001) and CSF (P < 0.001) of the EAP groups compared to the Control groups. Therefore, IL-1β was identified as the target PDIC which crosses the blood-brain barrier, thereby influencing the central nervous system. Moreover, the EAP-1 subgroup displayed a gradually prolonged ejaculation latency (EL) in the last three CBTs (all P < 0.01) and a significantly lower expression of NMDA NR1 subunit in the PVN (P = 0.043) compared to the respective control groups after a 10-day central administration of IL-1β inhibitors. However, the Control-1 subgroup showed a gradually shortened EL (P < 0.01) and a significantly higher NR1 expression (P = 0.004) after homochronous IL-1β administration. Therefore, we identified IL-1β as the primary PDIC which shortens EL in EAP rats. However, further studies should be conducted to elucidate the specific molecular mechanisms through which IL-1β upregulates NMDA expression.
Animals ; Cytokines/metabolism* ; Disease Models, Animal ; Ejaculation/physiology* ; Interleukin-1beta/metabolism* ; Male ; N-Methylaspartate/metabolism* ; Prostate/metabolism* ; Prostatitis/metabolism* ; Rats ; Receptors, N-Methyl-D-Aspartate/metabolism*

CaMKII is essential for long-term potentiation (LTP), a process in which synaptic strength is increased following the acquisition of information. Among the four CaMKII isoforms, γCaMKII is the one that mediates the LTP of excitatory synapses onto inhibitory interneurons (LTP_E→I). However, the molecular mechanism underlying how γCaMKII mediates LTP_E→I remains unclear. Here, we show that γCaMKII is highly enriched in cultured hippocampal inhibitory interneurons and opts to be activated by higher stimulating frequencies in the 10-30 Hz range. Following stimulation, γCaMKII is translocated to the synapse and becomes co-localized with the postsynaptic protein PSD-95. Knocking down γCaMKII prevents the chemical LTP-induced phosphorylation and trafficking of AMPA receptors (AMPARs) in putative inhibitory interneurons, which are restored by overexpression of γCaMKII but not its kinase-dead form. Taken together, these data suggest that γCaMKII decodes NMDAR-mediated signaling and in turn regulates AMPARs for expressing LTP in inhibitory interneurons.
Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism* ; Hippocampus/metabolism* ; Interneurons/physiology* ; Long-Term Potentiation/physiology* ; N-Methylaspartate/metabolism* ; Receptors, AMPA/physiology* ; Receptors, N-Methyl-D-Aspartate/metabolism* ; Synapses/physiology*

A 24-year-old nulligravida who presented with seizures and behavioral changes with prodrome of flu-like symptoms was initially treated as a case of viral encephalitis. Neurologic diagnostic tests including electroencephalogram, cerebrospinal fluid analysis (CSF), and cranial magnetic resonance imaging were done and inconclusive. Patient's seizure attacks persisted and her neurologic status was deteriorating despite giving appropriate anti-epileptic medications, hence an autoimmune disease was highly considered. The CSF was positive for N-methyl-D-aspartate receptor antibodies. This prompted a search for an associated teratoma and revealed a diagnostic dilemma between presence of an ovarian new growth versus a normal enlarged ovary. Laparoscopy which is both diagnostic and therapeutic was utilized. This report highlights prompt recognition of a rare case and prevented its progression to a potentially fatal condition as resection of the tumor dramatically relieved the symptoms. The significance of minimally invasive surgery in managing this case, effect in fertility, and possible association with pelvic inflammatory disease are also discussed.
Laparoscopy ; N-Methylaspartate ; Teratoma

Brain ; N-Methylaspartate ; Neurons ; Patch-Clamp Techniques

BACKGROUND: Autism is a challenging neurodevelopmental disorder. Previous clinical observations have suggested altered sedation requirements for children with autism. Our study aimed to test this observation experimentally in an animal model and to explore its possible mechanisms. METHODS: Eight adult pregnant female Sprague-Dawley rats were randomly divided into two groups. Four were injected with intraperitoneal sodium valproate on gestational day 12 and four were injected with normal saline. On postnatal day 28, the newborn male rats were subjected to the open-field test to confirm autistic features. Each rat was injected intraperitoneally with a single dose of propofol (50 mg/kg) or dexmedetomidine (0.2 mg/kg). The times to loss of righting reflex (LORR) and to return of righting reflex (RORR) were recorded. On the following day, all rats were re-sedated and underwent electroencephalography (EEG). Thereafter, the rats were euthanized and their hippocampal gamma-aminobutyric acid type A (GABA(A)) and glutamate N-methyl-D-aspartate (NMDA) receptor gene expressions were assessed. RESULTS: Autistic rats showed significantly longer LORR times and shorter RORR times than did the controls (median LORR times: 12.0 versus 5.0 min for dexmedetomidine and 22.0 versus 8.0 min for propofol; P < 0.05). EEG showed a low-frequency, high-amplitude wave pattern 2 min after LORR in the control rats. Autistic rats showed a high-frequency, low-amplitude awake pattern. Hippocampal GABA(A) receptor gene expression was significantly lower and NMDA gene expression was greater in autistic rats. CONCLUSIONS: This study supports the clinical observations of increased anesthetic sedative requirements in children with autism and our biochemical analyses using and glutamate receptor gene expression highlight possible underlying mechanisms.
Adult ; Animals ; Autistic Disorder ; Child ; Dexmedetomidine ; Electroencephalography ; Female ; gamma-Aminobutyric Acid ; Gene Expression ; Glutamic Acid ; Humans ; Infant, Newborn ; Male ; Models, Animal ; N-Methylaspartate ; Neurodevelopmental Disorders ; Propofol ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA-A ; Receptors, Glutamate ; Reflex, Righting ; Valproic Acid

Opioids are important drugs for the management of severe cancer pain without a ceiling effect. However, opioid administration leads to dose-limiting complications including drowsiness, hallucinations, delirium, respiratory depression, cognitive impairment, seizure, myoclonus, and hyperalgesia. Opioid-induced hyperalgesia (OIH) is a paradoxical phenomenon as opioid exposure increases pain sensitivity. Reducing or stopping opioids, opioid rotation, or co-administration of N-methyl-D-aspartate (NMDA) antagonists have been suggested for the management of OIH. In this study, we report two clinical cases of successful management of OIH in cancer pain patients that were treated with opioids.
Analgesics, Opioid ; Cognition Disorders ; Delirium ; Hallucinations ; Humans ; Hyperalgesia ; Myoclonus ; N-Methylaspartate ; Pain Management ; Respiratory Insufficiency ; Seizures ; Sleep Stages

Dysregulation of excitatory neurotransmission has been implicated in the pathogenesis of neuropsychiatric disorders. Pharmacological inhibition of N-methyl-D-aspartate (NMDA) receptors is widely used to model neurobehavioral pathologies and underlying mechanisms. There is ample evidence that overstimulation of NMDA-dependent neurotransmission may induce neurobehavioral abnormalities, such as repetitive behaviors and hypersensitization to nociception and cognitive disruption, pharmacological modeling using NMDA has been limited due to the induction of neurotoxicity and blood brain barrier breakdown, especially in young animals. In this study, we examined the effects of intraperitoneal NMDA-administration on nociceptive and repetitive behaviors in ICR mice. Intraperitoneal injection of NMDA induced repetitive grooming and tail biting/licking behaviors in a dose- and age-dependent manner. Nociceptive and repetitive behaviors were more prominent in juvenile mice than adult mice. We did not observe extensive blood brain barrier breakdown or neuronal cell death after peritoneal injection of NMDA, indicating limited neurotoxic effects despite a significant increase in NMDA concentration in the cerebrospinal fluid. These findings suggest that the observed behavioral changes were not mediated by general NMDA toxicity. In the hot plate test, we found that the latency of paw licking and jumping decreased in the NMDA-exposed mice especially in the 75 mg/kg group, suggesting increased nociceptive sensitivity in NMDA-treated animals. Repetitive behaviors and increased pain sensitivity are often comorbid in psychiatric disorders (e.g., autism spectrum disorder). Therefore, the behavioral characteristics of intraperitoneal NMDA-administered mice described herein may be valuable for studying the mechanisms underlying relevant disorders and screening candidate therapeutic molecules.
Adult ; Animals ; Autistic Disorder ; Blood-Brain Barrier ; Cell Death ; Cerebrospinal Fluid ; Grooming ; Humans ; Injections, Intraperitoneal ; Mass Screening ; Mice ; Mice, Inbred ICR ; N-Methylaspartate ; Neurons ; Nociception ; Pathology ; Synaptic Transmission ; Tail

BACKGROUND: This study investigated the role of NR2B in a modulated pain process in the painful diabetic neuropathy (PDN) rat using various pain stimuli. METHODS: Thirty-two Sprague-Dawley male rats were randomly allocated into four groups (n=8): control, diabetes mellitus (DM) rats and diabetic rats treated with ifenprodil at a lower dose (0.5 µg/day) (I 0.5) or higher dose (1.0 µg/day) (I 1.0). DM was induced by a single injection of streptozotocin at 60 mg/kg on day 0 of experimentation. Diabetic status was assessed on day 3 of the experimentation. The responses on both tactile and thermal stimuli were assessed on day 0 (baseline), day 14 (pre-intervention), and day 22 (post-intervention). Ifenprodil was given intrathecally for 7 days from day 15 until day 21. On day 23, 5% formalin was injected into the rats' hind paw and the nociceptive responses were recorded for 1 hour. The rats were sacrificed 72 hours post-formalin injection and an analysis of the spinal NR2B expression was performed. RESULTS: DM rats showed a significant reduction in pain threshold in response to the tactile and thermal stimuli and higher nociceptive response during the formalin test accompanied by the higher expression of phosphorylated spinal NR2B in both sides of the spinal cord. Ifenprodil treatment for both doses showed anti-allodynic and anti-nociceptive effects with lower expression of phosphorylated and total spinal NR2B. CONCLUSION: We suggest that the pain process in the streptozotocin-induced diabetic rat that has been modulated is associated with the higher phosphorylation of the spinal NR2B expression in the development of PDN, which is similar to other models of neuropathic rats.
Animals ; Diabetes Mellitus ; Diabetic Neuropathies ; Formaldehyde ; Humans ; Hyperalgesia ; Male ; N-Methylaspartate ; Pain Measurement ; Pain Threshold ; Phosphorylation ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; Spinal Cord ; Streptozocin

Despite some innate limitations, animal models are a potent investigative tool when used to model specific symptoms of a disorder. For example, MK-801, an N-methyl-D-aspartate receptor antagonist, is used as a pharmacological tool to induce symptoms found in some neuropsychiatric disorders. However, a close examination of literature suggests that the application window of MK-801 doses is relatively narrow between individual behavioral paradigms, necessitating careful characterization of the evoked behavioral aberrations and the doses used to induce them. Moreover, variation in behaviors depending on the animal strain, gender of the subject, and the timing of administration is observed, making it difficult to compare the behavioral characteristics reported in different studies. We aim to characterize the behavioral aberrations induced by different doses of MK-801 in CD-1 mice and create a ready reference for future studies. We used CD-1 mice to recapitulate behavioral impairments resulting from acute administration of MK-801. In 0.1 mg kg⁻¹, we observed diminished spontaneous alteration during the Y-maze test, while 0.12 mg kg⁻¹ resulted in hyperlocomotion and social deficit. Mice treated with 0.2 and 0.3 mg kg⁻¹ of MK-801 demonstrated a decreased self-grooming. Finally, all doses significantly impaired cliff avoidance behaviors suggesting increased impulsivity. These results affirm that MK-801 can effectively model various symptoms of different neuropsychiatric disorders in a dose-dependent manner. The observed sensitivity against spatial-memory impairment and impulsive behaviors at low concentration of MK-801 suggest that MK801 may modulate cognitive function and impulsivity in even lower concentration before it can modulate other behavioral domains.
Animals ; Avoidance Learning ; Cognition ; Dizocilpine Maleate ; Impulsive Behavior ; Mice ; Models, Animal ; N-Methylaspartate