Adenosine A1 receptor antagonist-induced facilitation of postsynaptic AMPA currents in pyramidal neurons of the rat hippocampal CA2 area.

Adenosine A1 receptors (A1R) are widely expressed in hippocampal pyramidal neurons and their presynaptic terminals. It is well known that endogenous adenosine regulates hippocampal function through the activation of A1R in hippocampal pyramidal neurons and has been reported that blockade of A1R induces stronger potentiation of excitatory synaptic transmission in CA2 pyramidal neurons than in CA1 pyramidal neurons. This strong potentiation of CA2 neurons is thought to be caused by the specific modulation of excitatory synaptic transmission through postsynaptic A1R. However, the direct effects of A1R on postsynaptic AMPA channels remain unknown because of the technical difficulties of patch-clamp recording from mature hippocampal CA2 neurons. We recorded synaptic currents from pyramidal neurons in CA1 and CA2 and analyzed the effects of an A1R antagonist on stimulation-evoked synaptic transmission and local application-induced postsynaptic AMPA currents. The antagonist increased the amplitude of evoked synaptic transmission in neurons in both CA1 and CA2. This facilitation was larger in pyramidal neurons in CA2 than in CA1. The antagonist also increased postsynaptic AMPA currents in neurons in CA2 but not in CA1. This facilitation of CA2 AMPA currents was occluded by the intracellular application of a G-protein blocker. Even with the blockade of postsynaptic G-protein signaling, the A1R antagonist increased evoked synaptic transmission in neurons in CA2. These results suggest that synaptic transmission in pyramidal neurons in CA2 is regulated by both presynaptic and postsynaptic A1R. Moreover, A1R regulate excitatory synaptic transmission in pyramidal neurons in CA2 through the characteristic postsynaptic modulation of AMPA currents.

Leucine-Enriched Essential Amino Acids Enhance the Antiseizure Effects of the Ketogenic Diet in Rats.

The classic ketogenic diet (KD) can be used successfully to treat medically refractory epilepsy. However, the KD reduces seizures in 50-70% of patients with medically refractory epilepsy, and its antiseizure effect is limited. In the current study, we developed a new modified KD containing leucine (Leu)-enriched essential amino acids. Compared with a normal KD, the Leu-enriched essential amino acid-supplemented KD did not change the levels of ketosis and glucose but enhanced the inhibition of bicuculline-induced seizure-like bursting in extracellular recordings of acute hippocampal slices from rats. The enhancement of antiseizure effects induced by the addition of Leu-enriched essential amino acids to the KD was almost completely suppressed by a selective antagonist of adenosine A1 receptors or a selective dose of pannexin channel blocker. The addition of Leu-enriched essential amino acids to a normal diet did not induce any antiseizure effects. These findings indicate that the enhancement of the antiseizure effects of the KD is mediated by the pannexin channel-adenosine A1 receptor pathway. We also analyzed amino acid profiles in the plasma and hippocampus. A normal KD altered the levels of many amino acids in both the plasma and hippocampus. The addition of Leu-enriched essential amino acids to a KD further increased and decreased the levels of several amino acids, such as threonine, histidine, and serine, suggesting that altered metabolism and utilization of amino acids may play a role in its antiseizure effects. A KD supplemented with Leu-enriched essential amino acids may be a new therapeutic option for patients with epilepsy, including medically refractory epilepsy.

Sorafenib Rechallenge and Sorafenib after Lenvatinib Failure in a Patient with Hepatocellular Carcinoma.

A 70-year-old man was diagnosed with multiple lung metastases from hepatocellular carcinoma, and lenvatinib was initiated. Three months later, the response was progressive disease. Sorafenib therapy as a second-line drug was started. Three months later, the lung metastases had shrunk. After the sorafenib failure, the patient received regorafenib treatment for six months until failure. After the regorafenib failure, sorafenib rechallenge therapy as a fourth-line treatment was initiated. The sorafenib rechallenge, which continued for two months, induced a partial response. Sorafenib after lenvatinib failure and sorafenib rechallenge may be a good option, but further prospective studies are needed.

Adenosine and Ketogenic Treatments.

It is well known that the neuromodulator adenosine, acting through the adenosine A1 receptor subtype, can limit or stop seizures. In 2008, adenosine was proposed as a key component of the anticonvulsant mechanism of the ketogenic diet (KD), a very low carbohydrate diet that can be highly effective in drug-refractory epilepsy. In this study, we review the accumulated data on the intersection among adenosine, ketosis, and anticonvulsant/antiepileptogenic effects. In several rodent models of epilepsy and seizures, antiseizure effects of ketogenic treatments (the KD itself, exogenous ketone bodies, medium-chain triglycerides or fatty acids) are reversed by administration of an adenosine A1 receptor antagonist. In addition, KD treatment elevates extracellular adenosine and tissue adenosine content in brain. Efforts to maintain or mimic a ketogenic milieu in brain slices reveal a state of reduced excitability produced by pre- and postsynaptic adenosine A1 receptor-based effects. Long-lasting seizure reduction may be due to adenosine-based epigenetic effects. In conclusion, there is accumulating evidence for an adenosinergic anticonvulsant action in the ketogenic state. In some cases, the main trigger is mildly but consistently lowered glucose in the brain. More research is needed to investigate the importance of adenosine in the antiepileptogenic and neuroprotective effects of these treatments. Future research may begin to investigate alternative adenosine-promoting strategies to enhance the KD or to find use as treatments themselves.

[Prediction of pancreatitis following endoscopic retrograde cholangiopancreatography].

OBJECTIVE: The aim of this study was to determine if the difference in serum amylase levels prior to, and two hours following, an endoscopic retrograde cholangiopancreatography (ERCP), or the ratio of the two-hour post-ERCP amylase level to the pre-ERCP amylase level was a better predictor of post-ERCP pancreatitis (PEP). METHODS: This was a retrospective, single-center study of consecutive patients, who underwent ERCP between April 2015 and August 2018. Serum amylase was measured before and two hours following ERCP. We compared the difference and the ratio of the two levels in predicting PEP using a receiver operating characteristic (ROC) curve analysis. RESULTS: A total of 1029 patients underwent ERCP, with PEP occurring in 118 (11.5%). Multivariate analysis revealed that an elevated two-hour post-ERCP serum amylase level was a significant predictor of PEP. ROC analysis of the difference and the ratio of the two levels found good performance for both parameters, with an area under the curve (AUC) of 0.861 (95% confidence interval [CI], 0.823-0.900) and 0.847 (95% CI, 0.809-0.886), respectively. The difference between the values was a significantly more effective predictor of PEP, based on the AUC analysis (P = 0.011). CONCLUSION: The difference between pre and two-hour post-ERCP amylase levels is a better predictor of PEP than the ratio of the two.

Mild hypothermia protects synaptic transmission from experimental ischemia through reduction in the function of nucleoside transporters in the mouse hippocampus.

Ischemia, a severe metabolic stress, increases adenosine levels and causes the suppression of synaptic transmission through adenosine A1 receptors. Although temperature also regulates extracellular adenosine levels, the effect of temperature on ischemia-induced activation of adenosine receptors is not yet fully understood. Here we examined the role of adenosine A1 receptors in mild hypothermia-mediated neuroprotection during the acute phase of ischemia. Severe ischemia-induced neurosynaptic impairment was reproduced by oxygen-glucose deprivation at normothermia (36 °C) and assessed with extracellular recordings or whole-cell patch clamp recordings in acute hippocampal slices in mice. Mild hypothermia (32 °C) induced the protection of synaptic transmission by activating adenosine A1 receptors. Stricter hypothermia (28 °C) caused additional neuroprotective effects by extending the onset time to anoxic depolarization; however, this effect was not associated with adenosine A1 receptors. The response of exogenous adenosine-induced inhibition of hippocampal synaptic transmission was increased by lowering the temperature to 32 °C or 28 °C. Hypothermia also reduced the function of dipryidamole-sensitive nucleoside transporters. These findings suggest that an increased response of adenosine A1 receptors, caused by a reduction in the function of nucleoside transporters, is one mechanism by which therapeutic hypothermia (usually used within the mild range) mediates neurosynaptic protection in the acute phase of stroke.

[Vitamin K deficiency caused by nutritional malabsorption accompanying afferent loop obstruction:a case report].

This case involves a 73-year-old man who visited a clinic because he was experiencing dyspnea on exertion and acid reflux. He was diagnosed with anemia and referred for a medical check-up and treatment by his primary care physician. Iron deficiency anemia and prolonged prothrombin time were confirmed with a blood test and an abdominal enhanced CT revealed marked expansion of the afferent loop after a gastrectomy. The medical check-up revealed abnormal blood coagulation due to afferent loop obstruction, which resulted in vitamin K deficiency. He was supplemented with vitamin K, and surgery was performed for the afferent loop obstruction. Postoperatively, his anemia, nutritional status, serum vitamin K levels, and prothrombin time improved steadily. In conclusion, nutrient malabsorption may occur in cases of afferent loop obstruction and abnormal blood coagulation due to vitamin K deficiency.

[Successful biliary drainage by percutaneous transhepatic puncture common bile duct and rendezvous technique for a case of recurrent biliary pancreatitis with a Roux-en-Y reconstruction and without extension of the bile duct].

A 92-year-old woman was hospitalized with upper abdominal pain. She had a history of acute biliary pancreatitis and chronic heart failure and had undergone gastrectomy with Roux-en-Y reconstruction. She was admitted with recurrent pancreatitis and an exacerbation of heart failure. Biliary drainage could not successfully be achieved endoscopically or with percutaneous transhepatic biliary drainage and EUS-guided biliary drainage because of the Roux-en-Y reconstruction and non-dilation of bile duct. We successfully accomplished biliary drainage in one session with percutaneous transhepatic puncture of the common bile duct with ultrasound guidance and the rendezvous technique. We report this case because it is rare.

Adenosine A1 receptor-mediated protection of mouse hippocampal synaptic transmission against oxygen and/or glucose deprivation: a comparative study.

Adenosine receptors are widely expressed in the brain, and adenosine is a key bioactive substance for neuroprotection. In this article, we clarify systematically the role of adenosine A1 receptors during a range of timescales and conditions when a significant amount of adenosine is released. Using acute hippocampal slices obtained from mice that were wild type or null mutant for the adenosine A1 receptor, we quantified and characterized the impact of varying durations of experimental ischemia, hypoxia, and hypoglycemia on synaptic transmission in the CA1 subregion. In normal tissue, these three stressors rapidly and markedly reduced synaptic transmission, and only treatment of sufficient duration led to incomplete recovery. In contrast, inactivation of adenosine A1 receptors delayed and/or lessened the reduction in synaptic transmission during all three stressors and reduced the magnitude of the recovery significantly. We reproduced the responses to hypoxia and hypoglycemia by applying an adenosine A1 receptor antagonist, validating the clear effects of genetic receptor inactivation on synaptic transmission. We found activation of adenosine A1 receptor inhibited hippocampal synaptic transmission during the acute phase of ischemia, hypoxia, or hypoglycemia and caused the recovery from synaptic impairment after these three stressors using genetic mutant. These studies quantify the neuroprotective role of the adenosine A1 receptor during a variety of metabolic stresses within the same recording system.NEW & NOTEWORTHY Deprivation of oxygen and/or glucose causes a rapid adenosine A1 receptor-mediated decrease in synaptic transmission in mouse hippocampus. We quantified adenosine A1 receptor-mediated inhibition during and synaptic recovery after ischemia, hypoxia, and hypoglycemia of varying durations using a genetic mutant and confirmed these findings using pharmacology. Overall, using the same recording conditions, we found the acute response and the neuroprotective ability of the adenosine A1 receptor depended on the type and duration of deprivation event.

Metabolic Therapy for Temporal Lobe Epilepsy in a Dish: Investigating Mechanisms of Ketogenic Diet using Electrophysiological Recordings in Hippocampal Slices.

The hippocampus is prone to epileptic seizures and is a key brain region and experimental platform for investigating mechanisms associated with the abnormal neuronal excitability that characterizes a seizure. Accordingly, the hippocampal slice is a common in vitro model to study treatments that may prevent or reduce seizure activity. The ketogenic diet is a metabolic therapy used to treat epilepsy in adults and children for nearly 100 years; it can reduce or eliminate even severe or refractory seizures. New insights into its underlying mechanisms have been revealed by diverse types of electrophysiological recordings in hippocampal slices. Here we review these reports and their relevant mechanistic findings. We acknowledge that a major difficulty in using hippocampal slices is the inability to reproduce precisely the in vivo condition of ketogenic diet feeding in any in vitro preparation, and progress has been made in this in vivo/in vitro transition. Thus far at least three different approaches are reported to reproduce relevant diet effects in the hippocampal slices: (1) direct application of ketone bodies; (2) mimicking the ketogenic diet condition during a whole-cell patch-clamp technique; and (3) reduced glucose incubation of hippocampal slices from ketogenic diet-fed animals. Significant results have been found with each of these methods and provide options for further study into short- and long-term mechanisms including Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels, vesicular glutamate transporter (VGLUT), pannexin channels and adenosine receptors underlying ketogenic diet and other forms of metabolic therapy.

Adenosine receptors and epilepsy: current evidence and future potential.

Adenosine receptors are a powerful therapeutic target for regulating epileptic seizures. As a homeostatic bioenergetic network regulator, adenosine is perfectly suited to establish or restore an ongoing balance between excitation and inhibition, and its anticonvulsant efficacy is well established. There is evidence for the involvement of multiple adenosine receptor subtypes in epilepsy, but in particular the adenosine A1 receptor subtype can powerfully and bidirectionally regulate seizure activity. Mechanisms that regulate adenosine itself are increasingly appreciated as targets to thus influence receptor activity and seizure propensity. Taken together, established evidence for the powerful potential of adenosine-based epilepsy therapies and new strategies to influence receptor activity can combine to capitalize on this endogenous homeostatic neuromodulator.

Ketogenic diet sensitizes glucose control of hippocampal excitability.

A high-fat low-carbohydrate ketogenic diet (KD) is an effective treatment for refractory epilepsy, yet myriad metabolic effects in vivo have not been reconciled clearly with neuronal effects. A KD limits blood glucose and produces ketone bodies from ß-oxidation of lipids. Studies have explored changes in ketone bodies and/or glucose in the effects of the KD, and glucose is increasingly implicated in neurological conditions. To examine the interaction between altered glucose and the neural effects of a KD, we fed rats and mice a KD and restricted glucose in vitro while examining the seizure-prone CA3 region of acute hippocampal slices. Slices from KD-fed animals were sensitive to small physiological changes in glucose, and showed reduced excitability and seizure propensity. Similar to clinical observations, reduced excitability depended on maintaining reduced glucose. Enhanced glucose sensitivity and reduced excitability were absent in slices obtained from KD-fed mice lacking adenosine A1 receptors (A1Rs); in slices from normal animals effects of the KD could be reversed with blockers of pannexin-1 channels, A1Rs, or KATP channels. Overall, these studies reveal that a KD sensitizes glucose-based regulation of excitability via purinergic mechanisms in the hippocampus and thus link key metabolic and direct neural effects of the KD.

Homeostatic control of brain function - new approaches to understand epileptogenesis.

Neuronal excitability of the brain and ongoing homeostasis depend not only on intrinsic neuronal properties, but also on external environmental factors; together these determine the functionality of neuronal networks. Homeostatic factors become critically important during epileptogenesis, a process that involves complex disruption of self-regulatory mechanisms. Here we focus on the bioenergetic homeostatic network regulator adenosine, a purine nucleoside whose availability is largely regulated by astrocytes. Endogenous adenosine modulates complex network function through multiple mechanisms including adenosine receptor-mediated pathways, mitochondrial bioenergetics, and adenosine receptor-independent changes to the epigenome. Accumulating evidence from our laboratories shows that disruption of adenosine homeostasis plays a major role in epileptogenesis. Conversely, we have found that reconstruction of adenosine's homeostatic functions provides new hope for the prevention of epileptogenesis. We will discuss how adenosine-based therapeutic approaches may interfere with epileptogenesis on an epigenetic level, and how dietary interventions can be used to restore network homeostasis in the brain. We conclude that reconstruction of homeostatic functions in the brain offers a new conceptual advance for the treatment of neurological conditions which goes far beyond current target-centric treatment approaches.

Ketogenic diet improves core symptoms of autism in BTBR mice.

Autism spectrum disorders share three core symptoms: impaired sociability, repetitive behaviors and communication deficits. Incidence is rising, and current treatments are inadequate. Seizures are a common comorbidity, and since the 1920's a high-fat, low-carbohydrate ketogenic diet has been used to treat epilepsy. Evidence suggests the ketogenic diet and analogous metabolic approaches may benefit diverse neurological disorders. Here we show that a ketogenic diet improves autistic behaviors in the BTBR mouse. Juvenile BTBR mice were fed standard or ketogenic diet for three weeks and tested for sociability, self-directed repetitive behavior, and communication. In separate experiments, spontaneous intrahippocampal EEGs and tests of seizure susceptibility (6 Hz corneal stimulation, flurothyl, SKF83822, pentylenetetrazole) were compared between BTBR and control (C57Bl/6) mice. Ketogenic diet-fed BTBR mice showed increased sociability in a three-chamber test, decreased self-directed repetitive behavior, and improved social communication of a food preference. Although seizures are a common comorbidity with autism, BTBR mice fed a standard diet exhibit neither spontaneous seizures nor abnormal EEG, and have increased seizure susceptibility in just one of four tests. Thus, behavioral improvements are dissociable from any antiseizure effect. Our results suggest that a ketogenic diet improves multiple autistic behaviors in the BTBR mouse model. Therefore, ketogenic diets or analogous metabolic strategies may offer novel opportunities to improve core behavioral symptoms of autism spectrum disorders.

Adenosine and autism: a spectrum of opportunities.

In rodents, insufficient adenosine produces behavioral and physiological symptoms consistent with several comorbidities of autism. In rodents and humans, stimuli postulated to increase adenosine can ameliorate these comorbidities. Because adenosine is a broad homeostatic regulator of cell function and nervous system activity, increasing adenosine's influence might be a new therapeutic target for autism with multiple beneficial effects. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

The relationship between the neuromodulator adenosine and behavioral symptoms of autism.

The neuromodulator adenosine is an endogenous sleep promoter, neuroprotector and anticonvulsant, and people with autism often suffer from sleep disruption and/or seizures. We hypothesized that increasing adenosine can decrease behavioral symptoms of autism spectrum disorders, and, based on published research, specific physiological stimuli are expected to increase brain adenosine. To test the relationship between adenosine and autism, we developed a customized parent-based questionnaire to assess child participation in activities expected to influence adenosine and quantify behavioral changes following these experiences. Parents were naive to study hypotheses and all conditions were pre-assigned. Results demonstrate significantly better behavior associated with events pre-established as predicted to increase rather than decrease or have no influence on adenosine. Understanding the physiological relationship between adenosine and autism could open new therapeutic strategies--potentially preventing seizures, improving sleep, and reducing social and behavioral dysfunction.

A ketogenic diet delays weight loss and does not impair working memory or motor function in the R6/2 1J mouse model of Huntington's disease.

Ketogenic diets are high in fat and low in carbohydrates, and have long been used as an anticonvulsant therapy for drug-intractable and pediatric epilepsy. Additionally, ketogenic diets have been shown to provide neuroprotective effects against acute and chronic brain injury, including beneficial effects in various rodent models of neurodegeneration. Huntington's disease is a progressive neurodegenerative disease characterized by neurological, behavioral and metabolic dysfunction, and ketogenic diets have been shown to increase energy molecules and mitochondrial function. We tested the effects of a ketogenic diet in a transgenic mouse model of Huntington's disease (R6/2 1J), with a focus on life-long behavioral and physiological effects. Matched male and female wild-type and transgenic mice were maintained on a control diet or were switched to a ketogenic diet fed ad libitum starting at six weeks of age. We found no negative effects of the ketogenic diet on any behavioral parameter tested (locomotor activity and coordination, working memory) and no significant change in lifespan. Progressive weight loss is a hallmark feature of Huntington's disease, yet we found that the ketogenic diet-which generally causes weight loss in normal animals-delayed the reduction in body weight of the transgenic mice. These results suggest that metabolic therapies could offer important benefits for Huntington's disease without negative behavioral or physiological consequences.

Long-term facilitation of spontaneous calcium oscillations in astrocytes with endogenous adenosine in hippocampal slice cultures.

It is well established that astrocytes release gliotransmitters and moderate neuronal activity in the central nervous system via intracellular Ca(2+) dynamics. Astrocytic Ca(2+) oscillations are one type of spontaneous Ca(2+) mobilization that occurs in astrocytes. However, the modulation of spontaneous astrocytic Ca(2+) oscillations, especially in pathophysiological conditions, is not yet fully understood. Here, we demonstrate that activation of adenosine receptors induces a long-lasting increase in the frequency of astrocytic Ca(2+) oscillations in rat hippocampal slice cultures. The long-term facilitation of the frequency of Ca(2+) oscillations was mediated by endogenous adenosine generated via breakdown of extracellular ATP by ecto-ATPase. We also demonstrate that local tissue injury with ultraviolet irradiation can cause this long-term facilitation of Ca(2+) oscillations via endogenous adenosine. Our data suggest that endogenous adenosine is one of the modulators of spontaneous astrocytic Ca(2+) oscillations in the rat hippocampus, and may play a significant role in altered Ca(2+) dynamics in astrocytes observed during pathophysiological conditions.

Metabolic autocrine regulation of neurons involves cooperation among pannexin hemichannels, adenosine receptors, and KATP channels.

Metabolic perturbations that decrease or limit blood glucose-such as fasting or adhering to a ketogenic diet-reduce epileptic seizures significantly. To date, the critical links between altered metabolism and decreased neuronal activity remain unknown. More generally, metabolic changes accompany numerous CNS disorders, and the purines ATP and its core molecule adenosine are poised to translate cell energy into altered neuronal activity. Here we show that nonpathological changes in metabolism induce a purinergic autoregulation of hippocampal CA3 pyramidal neuron excitability. During conditions of sufficient intracellular ATP, reducing extracellular glucose induces pannexin-1 hemichannel-mediated ATP release directly from CA3 neurons. This extracellular ATP is dephosphorylated to adenosine, activates neuronal adenosine A(1) receptors, and, unexpectedly, hyperpolarizes neuronal membrane potential via ATP-sensitive K(+) channels. Together, these data delineate an autocrine regulation of neuronal excitability via ATP and adenosine in a seizure-prone subregion of the hippocampus and offer new mechanistic insight into the relationship between decreased glucose and increased seizure threshold. By establishing neuronal ATP release via pannexin hemichannels, and hippocampal adenosine A(1) receptors coupled to ATP-sensitive K(+) channels, we reveal detailed information regarding the relationship between metabolism and neuronal activity and new strategies for adenosine-based therapies in the CNS.

Control of cannabinoid CB1 receptor function on glutamate axon terminals by endogenous adenosine acting at A1 receptors.

Marijuana is a widely used drug that impairs memory through interaction between its psychoactive constituent, Delta-9-tetrahydrocannabinol (Delta(9)-THC), and CB(1) receptors (CB1Rs) in the hippocampus. CB1Rs are located on Schaffer collateral (Sc) axon terminals in the hippocampus, where they inhibit glutamate release onto CA1 pyramidal neurons. This action is shared by adenosine A(1) receptors (A1Rs), which are also located on Sc terminals. Furthermore, A1Rs are tonically activated by endogenous adenosine (eADO), leading to suppressed glutamate release under basal conditions. Colocalization of A1Rs and CB1Rs, and their coupling to shared components of signal transduction, suggest that these receptors may interact. We examined the roles of A1Rs and eADO in regulating CB1R inhibition of glutamatergic synaptic transmission in the rodent hippocampus. We found that A1R activation by basal or experimentally increased levels of eADO reduced or eliminated CB1R inhibition of glutamate release, and that blockade of A1Rs with caffeine or other antagonists reversed this effect. The CB1R-A1R interaction was observed with the agonists WIN55,212-2 and Delta(9)-THC and during endocannabinoid-mediated depolarization-induced suppression of excitation. A1R control of CB1Rs was stronger in the C57BL/6J mouse hippocampus, in which eADO levels were higher than in Sprague Dawley rats, and the eADO modulation of CB1R effects was absent in A1R knock-out mice. Since eADO levels and A1R activation are regulated by homeostatic, metabolic, and pathological factors, these data identify a mechanism in which CB1R function can be controlled by the brain adenosine system. Additionally, our data imply that caffeine may potentiate the effects of marijuana on hippocampal function.