Renin-Angiotensin-Aldosterone System Inhibitors Prevent the Onset of Oxaliplatin-Induced Peripheral Neuropathy: A Retrospective Multicenter Study and in Vitro Evaluation.

Oxaliplatin (OXA) is used in chemotherapy for various cancer types and is associated with acute and chronic neurotoxicity. However, a preventive strategy for OXA-induced peripheral neuropathy (OIPN) and its underlying mechanism remain unclear. We examined the effects of renin-angiotensin-aldosterone system inhibitors (RAASIs) on OIPN by performing a retrospective multicenter study and an in vitro assay. We retrospectively evaluated electronic medical records of 976 patients who underwent one or more courses of OXA-containing regimens at Ehime, Okayama, and Tokushima University Hospitals. The primary endpoint was the incidence of OIPN during or after OXA administration. The effects of RAASIs and OXA on the neurite length in PC12 cells were determined. The combined administration of an OXA-containing regimen and RAASI significantly inhibited the cumulative incidence grade-2 or higher OIPN (log-rank test; p = 0.0001). RAASIs markedly suppressed the development of both acute and chronic OIPN (multivariate analysis; p = 0.017 and p = 0.011). In an in vitro assay, 10 µM OXA suppressed the neurite length; treatment with 1 µM aliskiren, spironolactone, 10 µM candesartan, and enalapril significantly restored neurite length to the control level. Moreover, 1 µM SCH772984 (a selective inhibitor of extracellular signal-regulated kinase, ERK1/2) and 500 µM SQ22536 (a cell-permeable adenylate cyclase (AC) inhibitor) markedly abolished neurite-extending effects of candesartan and enalapril. These results indicate that RAASIs possess preventive or therapeutic effects in acute and chronic OIPN, candesartan and enalapril may increase in the activity of ERK1/2 and AC in PC12 cells.

Clinical effectiveness of switching between DPP-4 inhibitors in patients with type 2 diabetes mellitus
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OBJECTIVES: Dipeptidyl peptidase-4 inhibitors (DPP-4Is) can be classified into three categories according to their binding subsites. We wished to clarify the efficacy of switching between DPP-4Is according to their binding subsites. MATERIALS AND METHODS: We undertook a retrospective study of the medical records of patients who switched from one DPP-4I to another. RESULTS: Among 62 patients eligible for study inclusion, the mean change in the glycated hemoglobin (HbA1c) level between different categories of DPP-4I was -0.35 (95% CI, -0.12 to -0.58; n = 59). The mean change in the HbA1c level between each class of DPP-4I was calculated. From class 3 to class 2 it was -0.45 (n = 25); from class 3 to class 1 it was -0.36 (n = 17); from class 1 to class 2 it was -0.24 (n = 7); from class 1 to class 3 it was 0.33 (n = 4); from class 2 to class 1 it was -0.30 (n = 5); from class 2 to class 3 it was -1.30 (n = 1). CONCLUSIONS: When switching DPP-4Is because of insufficient efficacy, consideration of their DPP-4 binding site may be beneficial.

Effect of Eucommia ulmoides Leaf Extract on Chronic Dextran Sodium Sulfate-Induced Colitis in Mice.

Ulcerative colitis (UC) is a refractory disease that causes chronic inflammation or ulceration in the mucosa of the large intestine with multiple relapses. Although several drugs, including 5-aminosalicylic acid, steroids, immunosuppressants, and infliximab, are used for UC therapy, patients suffer from side effects of these drugs, and a new safer therapeutic agent is desired. Eucommia ulmoides OLIV. leaf extract (ELE) has an anti-inflammatory effect. Therefore, we examined the effect of ELE on UC using a chronic dextran sulfate sodium (DSS)-induced colitis model in mice. Chronic DSS-induced colitis was triggered by alternately repeating 5 days' DSS and 7 days' water administration in mice for 29 d. The severity of DSS-induced colitis was evaluated by daily body weight and bloody stool score, and colon length and myeloperoxidase (MPO) activity in colon tissue on day 29. ELE (3 or 9%) was administered in combination by feeding for 29 d, and the effect on colitis was evaluated. The mice given DSS exhibited chronic colitis symptoms with body weight loss, increased bloody stool score and MPO activity, and shortened colon length. Administration of 3 or 9% ELE suppressed the body weight loss, bloody stool score, colon shortening, and MPO activity in a dose-dependent manner. Histological analysis showed that the ELE-treated mice had less damages and leukocyte infiltration in the mucosal layer of the large intestine compared to DSS alone group. These results suggested that ELE has the potential to prevent the development of DSS-induced colitis and a therapeutic effect on UC in a safe manner.

Predictive Performance of Vancomycin Trough Concentrations in Patients With Diabetes With Microalbuminuria.

BACKGROUND: The performance of a population pharmacokinetic model in predicting trough concentrations after the initial vancomycin dose was evaluated in patients with albuminuria compared with patients who did not have albuminuria. METHODS: Data were collected from 52 patients infected with methicillin-resistant Staphylococcus aureus (excluding patients undergoing dialysis and acute kidney injury) and treated with vancomycin. The data included urinary albumin concentration. RESULTS: The calculated mean prediction error and mean absolute error for the serum trough concentrations of vancomycin (with 95% confidence intervals) were 4.65 (4.13-5.17) and 6.1 (5.65-6.51), respectively, in microalbuminuria and 0.33 (-0.2 to 0.86) and 4.02 (3.59-4.45), respectively, in those without. There was no significant difference observed in serum creatinine concentration, age, weight, estimation of vancomycin trough concentration in serum, and actual trough concentration of vancomycin in serum between individuals with microalbuminuria and those without albuminuria. CONCLUSIONS: Microalbuminuria in patients with diabetes is a marker of the difference between predicted vancomycin trough concentrations and actual vancomycin trough concentrations.

Valproic acid reduces hair loss and improves survival in patients receiving temozolomide-based radiation therapy for high-grade glioma.

PURPOSE: Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, is also used to manage seizures in glioblastoma patients. HDAC inhibitors can protect normal cells and tissues from the deleterious effects of radiotherapy, and VPA is reported to improve the survival of glioblastoma patients receiving chemoradiation therapy. VPA also promotes hair growth, and thus has the potential to reduce the radiotherapy side effect of hair loss while improving the survival of patients with glioblastoma. The purpose of this study was to determine whether VPA use during radiotherapy for high-grade glioma is associated with decreased side effects of radiotherapy and an improvement in overall survival (OS) and progression-free survival (PFS). METHODS: Medical records of 112 patients with high-grade glioma were retrospectively reviewed. We grouped patients by VPA use or non-use during radiotherapy, and evaluated hair loss, OS, and PFS. RESULTS: The radiation dose and fractionation at the onset of hair loss were 4 Gy and two fractions higher, respectively, in the VPA group compared with the VPA non-use group (P < 0.01). Median OS was 42.2 and 20.3 months in the VPA use and non-use groups, respectively (P < 0.01; hazard ratio [HR], 0.36; 95% confidence interval [CI], 0.18-0.74). Median PFS was 22.7 and 11.0 months in the VPA use and non-use groups, respectively (P = 0.099; HR, 0.62; 95% CI, 0.36-1.09). CONCLUSIONS: VPA use during radiotherapy for glioma is associated with delayed hair loss and improvement in survival. Hair loss prevention benefits patients suffering from the deleterious effects of radiation.

Psychiatric Patients with Antipsychotic Drug-Induced Hyperprolactinemia and Menstruation Disorders.

Treatment with antipsychotic drugs has been associated with hyperprolactinemia. The same antipsychotic drugs have also been associated with side effects such as menstruation disorders. The aim of this study was to evaluate the prevalence of hyperprolactinemia and menstruation disorders in women undergoing antipsychotic treatment. We performed a retrospective chart review study of psychiatric patients who underwent laboratory testing for serum prolactin (PRL) level between March 2011 and March 2015 in Ehime University Hospital. Patients presenting with and without menstruation disorders were evaluated to determine if they presented concomitant hyperprolactinemia. Patients with menstrual disorders had a significant increase in serum PRL level with a mean of approximately 90 ng/mL. Those with menstrual disorders presented increased PRL levels by 2-fold that of patients without menstrual disorder. However, there was no significant difference in the equivalent dose of chlorpromazine between these two groups. Additionally, about 70% of patients with menstrual disorders received risperidone treatment. The receiver operating characteristic curve showed that the optimal cutoff point of serum PRL level associated with the development of menstrual disorders was 60 ng/mL. Based on these results, we concluded that patients with menstrual disorders presented increased serum PRL, and that most of them underwent treatment with risperidone.

Evaluation of factors associated with the achievement of an optimal teicoplanin trough concentration
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OBJECTIVE: Because teicoplanin has a long serum half-life, a longer period of time is needed to achieve a steady-state concentration compared with vancomycin. The administration of an initial loading dose has been recommended to reach an effective teicoplanin serum concentration for the treatment of methicillin-resistant Staphylococcus aureus (MRSA). However, little is known regarding factors that affect teicoplanin concentration. This study aimed to retrospectively determine which factors are associated with achieving an optimal teicoplanin trough level. METHODS: We analyzed patients with MRSA infections who were treated with teicoplanin intravenously between January 2010 and July 2014. The effect of loading dose administration was evaluated in patients treated with 1,200 mg or 1,600 mg of teicoplanin, respectively. RESULTS: Approximately 32% (31/97) of patients achieved the trough concentration target (≥ 15 µg/mL) on the 3rd or 4th day. Multivariate analysis showed that loading doses and body surface area (BSA) were associated with trough concentration > 15 µg/mL on the 3rd or 4th day. Moreover, patients treated with the 2-day loading dose (1,600 mg group: 800 mg/day on 2 days) promptly achieved a trough concentration > 15 µg/mL on the 3rd or 4th day compared with those receiving a 1-day loading dose (1,200 mg group: 800 mg/day on only 1 day). The receiver operating characteristic curve showed that the optimal cut-off point of estimated glomerular filtration rate (eGFR) was 56 mL/min with 1-day loading dose to achieve a trough concentration target > 15 µg/mL. CONCLUSION: These results suggested that patients with decreased renal function (eGFR < 56 mL/min) can safely achieve an optimal trough level with the 1-day loading dose. In patients with normal renal function (eGFR ≥ 56 mL/min), administration of a 2-day loading dose may be needed to rapidly achieve a trough concentration ≥ 15 µg/mL.
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Prolonged effects of miconazole oral gel on warfarin anticoagulation even after treatment withdrawal.

OBJECTIVE: We investigated the effect of terminating miconazole oral gel (MOG) treatment on the anticoagulant activity of warfarin by evaluating changes in international normalized ratio levels (INR). METHODS: Data were collected from the medical records of 6 patients treated with warfarin and MOG. RESULTS: Following cessation of MOG treatment, increased INR and INR/dose levels were observed for an average of 15 days, showing that the anticoagulant activity of warfarin was increased for ~ 2 weeks. CONCLUSIONS: Closer monitoring of INR levels for at least 2 weeks may be required upon withdrawal of MOG treatment in patients treated with warfarin.

Disruption of running activity rhythm following restricted feeding in female mice: Preventive effects of antidepressants.

Biological rhythms are critical in the etiology of mood disorders; therefore, effective mood disorder treatments should address rhythm disturbances. Among the variables synchronized with the light-dark cycle, spontaneous activity in rodents is useful for investigating circadian rhythms. However, previous studies have focused only on the increase of wheel-running activity under restricted feeding conditions, while little information is available on circadian rhythm of running activity. In this study, chronometrical analysis was used to assess whether circadian rhythms during wheel-running are altered by restricted feeding and affected by antidepressant drugs. Wheel revolutions were automatically recorded and analyzed using cosinor-rhythmometry in 8-week old ICR albino mice. When feeding was restricted to 1 h per day (21:00-22:00), wheel-running rhythms were reliably disrupted. Female mice exhibited marked alterations in the pattern and extent of wheel-running beginning on day 1. Subchronic treatment with imipramine or paroxetine, as well as tandospirone and (-)-DOI, prevented wheel-running rhythm disruption. Thus, altering the circadian activity rhythms of female mice on a 1-h feeding schedule may be useful for investigating disturbances in biological rhythms.

Evaluation of edaravone against radiation-induced oral mucositis in mice.

Oral mucositis induced by radiotherapy for cancers of the head and neck reduce the quality of life of patients. However, effective therapeutic agents are lacking. Symptomatic treatment involves local anesthesia and analgesia. We focused on the antioxidant effects of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one; Radicut(®)). Oral mucositis was induced on the tongue tips of mice using a single dose of X-rays (20 Gy). To evaluate the protective effect of edaravone (30 and 300 mg/kg), administration was carried out 30 min before irradiation. Survival, oral mucositis score, myeloperoxidase activity, and levels of 2-Thiobarbituric acid reactive substances were measured, and all were improved compared with those of control mice. A significant difference was not found in terms of survival due to edaravone. Histopathologic findings also highlighted the beneficial features of edaravone. Edaravone reduced the production of reactive oxygen species. These findings suggest that the protective effect of edaravone against radiation-induced oral mucositis is through an antioxidant effect.

Involvement of stimulation of α7 nicotinic acetylcholine receptors in the suppressive effect of tropisetron on dextran sulfate sodium-induced colitis in mice.

Ulcerative colitis (UC) involves chronic inflammation of the large intestine. Several agents are used to treat UC, but adverse side effects are remaining problems. We examined the effect of tropisetron as a new type of drug for UC using a dextran sulfate sodium (DSS)-induced model of colitis in mice. We developed a DSS-induced model of colitis and calculated the Disease Activity Index and colon length. We measured myeloperoxidase activity and determined the protein level and mRNA level of cytokines in the colon. DSS-induced colitis was ameliorated by administration of tropisetron and PNU282987. Pre-administration of methyllycaconitine diminished the suppressive effect of tropisetron upon DSS-induced colitis. These findings suggested that α7 nicotinic acetylcholine receptors (α7 nAChRs) were related to the suppressive effect of tropisetron on DSS-induced colitis. Additionally, stimulation of α7 nAChRs decreased the colon level of interleukin-6 and interferon-γ upon DSS administration. Furthermore, stimulation of α7 nAChRs decreased macrophage infiltration, with expression of α7 nAChR increased by DSS administration. These results suggest that the underlying mechanism of this suppressive effect on DSS-induced colitis is via stimulation of α7 nAChRs and involves suppression of expression of pro-inflammatory cytokines. Tropisetron could be a new type of therapeutic agent for UC.

Convulsive liability of cefepime and meropenem in normal and corneal kindled mice.

We have reported significantly higher convulsion prevalence in patients treated with cefepime than in those treated with meropenem. Additionally, cefepime-associated convulsions were found only in patients with brain disorders, not renal failure. Here, we compared the convulsive liability of cefepime and meropenem administered intravenously in normal and corneal kindled mice with low seizure thresholds. We used the proconvulsive test in normal mice following pentylenetetrazol (PTZ) injection and electroconvulsive shock at low-stimulus currents and in corneal kindled mice. We also measured electroencephalogram (EEG) activity 1 min after antibiotic injections. Intravenous injection of cefepime and meropenem at 250 or 500 mg/kg of body weight had no effect on PTZ-induced convulsions in normal mice. However, in convulsions induced by electroconvulsive shock at low-stimulus currents, mean seizure stage following cefepime administration at 500 mg/kg was significantly higher than that following saline injection. Additionally, EEG spikes were recorded for mice that were given cefepime (500 mg/kg). In corneal kindled mice following cefepime injection, mean seizure stage was significantly higher than that following meropenem injection. The convulsive liability of cefepime is significantly higher than that of meropenem in normal and corneal kindled mice. In patients with low seizure thresholds, convulsive liability of cefepime may be assumed.

Test-retest paradigm of the forced swimming test in female mice is not valid for predicting antidepressant-like activity: participation of acetylcholine and sigma-1 receptors.

The forced swimming test (FST) in mice is widely used to predict the antidepressant activity of a drug, but information describing the immobility of female mice is limited. We investigated whether a prior swimming experience affects the immobility duration in a second FST in female mice and whether the test-retest paradigm is a valid screening tool for antidepressants. Female ICR mice were exposed to the FST using two experimental paradigms: a single FST and a double FST in which mice had experienced FST once 24 h prior to the second trail. The initial FST experience reliably prolonged immobility duration in the second FST. The antidepressants imipramine and paroxetine significantly reduced immobility duration in the single FST, but not in the double FST. Scopolamine and the sigma-1 (σ1) antagonist NE-100 administered before the second trial significantly prevented the prolongation of immobility. Neither a 5-HT1A nor a 5-HT2A receptor agonist affected immobility duration. We suggest that the test-retest paradigm in female mice is not adequate for predicting antidepressant-like activity of a drug; the prolongation of immobility in the double FST is modulated through acetylcholine and σ1 receptors.

Oral mucosal adhesive films containing royal jelly accelerate recovery from 5-fluorouracil-induced oral mucositis.

Oral mucositis induced by chemotherapy or radiotherapy has an impact upon quality-of-life, is dose-limiting for chemotherapy, and causes considerable morbidity. We evaluated the effect of royal jelly (RJ) on 5-fluorouracil (5-FU)-induced oral mucositis in hamsters. Oral mucositis was induced in hamsters through a combination of 5-FU treatment and mild abrasion of the cheek pouch. RJ was contained in chitosan-sodium alginate film (RJ film). Films were attached to the oral mucosa and the healing process examined by measuring the area of mucositis, myeloperoxidase (MPO) activity, microscopic aspects, and RT-PCR for detection of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1ß). Furthermore, we evaluated the radical-scavenging activity of RJ and generation of keratinocyte growth factor from human periodontal ligament fibroblasts. RJ films (10%, 30%) significantly improved recovery from 5-FU-induced damage, reduced MPO activity and the production of pro-inflammatory cytokines. Additionally, RJ showed radical-scavenging activity. These data suggest that topical application of films that contain RJ had a healing effect on the severe oral mucositis induced by 5-FU and that the effect was caused by the anti-inflammatory or anti-oxidative activities of RJ.

Imipramine-induced c-Fos expression in the medial prefrontal cortex is decreased in the ACTH-treated rats.

Previous studies have shown that the antidepressive-like effect of tricyclic antidepressants is blocked by repeated treatments with adrenocorticotropic hormone (ACTH). However, little is known about the neuroanatomy underlying the mechanism of the imipramine treatment-resistant depression model. In the present study, first experimental evidence showed no significant difference of the serum imipramine concentrations between the saline and ACTH-treated rats. In further study, imipramine produced significant increases in the c-Fos expression in the medial prefrontal cortex (mPFC), the dentate gyrus of the hippocampus (DGH), and the central nucleus of the amygdala (CeA), in rats repeatedly treated with saline. The imipramine-increased c-Fos immunoreactivity was suppressed in the mPFC of rats repeatedly treated with ACTH. However, there was no significant difference in c-Fos expression in the DGH and CeA between ACTH- and saline-treated rats. These results suggest that the mPFC is maybe involved in effects of the imipramine in the ACTH-treated rats.

The assessment of risk for gastrointestinal injury with anticoagulant and antiplatelet drugs: the possible beneficial effect of eicosapentaenoic Acid for the risk of gastrointestinal injury.

Antithrombotic drugs have been increasingly used for treating ischemic cardiovascular diseases among the elderly in Japan. However, antithrombotic drugs are known to be risk factors for gastrointestinal injury. Therefore, we conducted a pharmacoepidemiologic study on patients receiving antithrombotic drugs to identify the risk factors for gastrointestinal injury. This retrospective case-control study included patients who were prescribed antithrombotic drugs at the Ehime University Hospital between April and September 2010. Of the 3271 patients who received antithrombotic drug therapy, 172 (5.3%) developed gastrointestinal injuries, including gastric ulcers, duodenal ulcers, and hemorrhagic gastrointestinal injuries. Further, the incidence of gastrointestinal injury was higher in patients with hypertension than in those without (p<0.0001). Multivariate adjusted odds ratios and 95% confidence intervals were calculated using stepwise logistic regression. The adjusted odds ratios for gastrointestinal injury were 1.56 (95% confidence interval 1.07-2.36) for hypertension, 1.70 (1.17-2.50) for low-dose aspirin, 2.77 (1.70-4.49) for clopidogrel, 1.95 (1.23-3.08) for warfarin, and 4.13 (2.88-5.95) for nonsteroidal anti-inflammatory drugs. On the other hand, the non-adjusted odds ratio for drug-associated gastrointestinal injury was 0.43 (0.20-0.84) for eicosapentaenoic acid (EPA). In addition, we found that patients aged 70 years or older were at increased risk of drug-associated gastrointestinal injury. These findings suggest that while many antithrombotic drugs are risk factors for gastrointestinal injury, EPA may be a safe option for suppressing or preventing gastrointestinal injury.

Treatment with linezolid in a neonate with meningitis caused by methicillin-resistant Staphylococcus epidermidis.

UNLABELLED: Recent findings have focused on the possible role of linezolid (LZD) as a suitable candidate for the treatment of central nervous system infections. LZD treatment for meningitis has been sporadically reported in adults, but there are no reports in neonates or infants. We report a case of meningitis caused by methicillin-resistant Staphylococcus epidermidis (MRSE) in a neonatal girl. The patient had intraventricular hemorrhage on postnatal day 1 and was treated with ventricular drainage. Twenty-two days after drainage, the patient developed a fever and seizure. Although ampicillin and ceftriaxone were given empirically for meningitis, an increased cell count and protein were observed in cerebrospinal fluid (CSF). Vancomycin (VCM) was administered intravenously because MRSE was detected from CSF 2 days after the administration of ampicillin and ceftriaxone. However, intravenous administration of VCM did not show any effect. Subsequent treatment of LZD successfully reduced the cell count and protein in CSF. CONCLUSION: LZD may be a treatment option for neonates and infants for drain-associated meningitis caused by MRSE.

A new method for evaluation of motivational effects of drugs.

Motivation is a process that continuously changes behavior to achieve a goal and can be conceptualized as a series of steps relating to that process. Intracranial self-stimulation (ICSS) behavior is considered to consist of reward and motivational effects. Moreover, priming stimulation of ICSS behavior is known to promote motivational effects. Using the runway method and priming stimulation, rewards and motivational effects of ICSS behavior can be differentiated. We investigated whether the runway method and priming stimulation of ICSS behavior could be used to evaluate motivational effects of a drug. In the ICSS runway model, running speed was considered as a reference of motivational effect. An assessment of pharmacological drugs known to influence motivational states was also undertaken. Using our experimental methods, prominent changes were observed in running speed when animals were administered methamphetamine and nicotine. Based on our results, we conclude that the runway method may be useful for the evaluation of substances that affect motivation. This review introduces 4 types of neuronal processes involved in motivation, reward mechanisms, outlines evaluation methods, and describes motivational properties of psychoactive drugs.

Involvement of dopaminergic receptor signaling in the effects of glutamatergic receptor antagonists on conditioned place aversion induced by naloxone in single-dose morphine-treated rats.

A better understanding of the neurochemical mechanisms mediating the aversive consequences of drug withdrawal is important for understanding drug addiction. We previously demonstrated that the inhibitory effect of glutamate receptor antagonists on the conditioned place aversion (CPA) induced by naloxone-precipitated withdrawal after a single morphine exposure could be blocked by dopamine receptor antagonists. Thus, a glutamatergic-dopaminergic interaction may participate in this phenomenon. The current study was undertaken to further characterize this interaction by employing both D(1) (SCH 23390) and D(2) (raclopride and eticlopride) dopamine receptor antagonists. The influence of these antagonists on the attenuation of CPA by MK-801 (NMDA receptor antagonist), GYKI 52466 (AMPA receptor antagonist), and MCPG (metabotropic glutamate receptor antagonist) was determined in rats receiving a single dose of morphine. The dopamine antagonists showed either a significant reversal or a tendency to reverse the effects of MK-801 on CPA. The effect of GYKI 52466 was also attenuated by the blockade of either D(1) or D(2) receptors. The effect of MCPG, however, was only blocked by D(2) antagonists and not by the D(1) antagonist SCH 23390. These results add evidence to the hypothesis that a glutamatergic-dopaminergic interaction may be involved in the CPA induced by naloxone-precipitated withdrawal following a single morphine exposure and suggest that both D(1) and D(2) dopamine receptor signaling mechanisms play a role in mediating the aversive aspects of acute dependence.

Effect of heat exposure on aminophylline-induced convulsions in mice.

Theophylline-associated convulsions are frequently exacerbated by fever, but the mechanisms behind it are still not completely understood. We investigated whether N-methyl-D-aspartic acid (NMDA) and gamma aminobutyric acid (GABA) receptors are involved in aminophylline (theophylline-2-ethylenediamine)-induced convulsions that are augmented by heat exposure-induced hyperthermia in mice. Mice exposed to 33 °C temperatures for 2 h had significantly increased body temperature (0.94 °C). Heat exposure significantly decreased time required for the onset of convulsions induced by an intraperitoneal (i.p.) injection of aminophylline (300 mg/kg). The shortened time for onset of convulsions was blocked by the NMDA receptor antagonist dizocilpine (0.1, 0.3 mg/kg, i.p.). However, the GABA(A) receptor agonist muscimol (1, 2 mg/kg, i.p.) did not have any effect. The pro-convulsant action of NMDA (100-125 mg/kg, i.p.) was enhanced by the heat exposure of 33 °C. However, the pro-convulsant actions of picrotoxin (3-4 mg/kg, i.p.), a GABA(A) receptor antagonist, were not affected by increased temperatures. These results suggest that NMDA receptors in the brain play a role in aminophylline-induced convulsions, which are augmented by heat exposure-induced hyperthermia in mice.