Faculty Bibliography

OBJECTIVE: Panayiotopoulos syndrome is a benign idiopathic childhood epilepsy characterized by altered autonomic activity at seizure onset. METHODS: Three siblings with Panayiotopoulos syndrome underwent 24-hour EEG recording and head-up tilt testing with continuous blood pressure and RR interval monitoring. Plasma catecholamines and vasopressin were measured while supine, upright, and during a typical seizure. RESULTS: Patient 1, a 12-year-old girl, had a history of involuntary lacrimation, abdominal pain, and recurrent episodes of loss of muscle tone and unresponsiveness followed by somnolence. Her EEG revealed bilateral frontotemporal spikes. Patient 2, a 10-year-old boy, had episodic headaches with pinpoint pupils, skin flushing of the face, trunk, and extremities, purple discoloration of hands and feet, diaphoresis, nausea, and vomiting. Tilt testing triggered a typical seizure after 9minutes; there was a small increase in blood pressure (+5/4mm Hg, systolic/diastolic) and pronounced increases in heart rate (+59bpm) and norepinephrine (+242pg/mL), epinephrine (+175pg/mL), and vasopressin (+22.1pg/mL) plasma concentrations. Serum glucose was elevated (206mg/dL). His EEG revealed right temporal and parietal spikes. Patient 3, an 8-year-old boy, had a history of restless legs at night, enuresis, night terrors, visual hallucinations, cyclic abdominal pain, and nausea. His EEG showed bitemporal spikes. CONCLUSION: Hypertension, tachycardia, and the release of vasopressin suggest activation of the central autonomic network during seizures in familial Panayiotopoulos syndrome. These autonomic and neuroendocrine features may be useful in the diagnosis and may have therapeutic implications

The extensive autophagic-lysosomal pathology in Alzheimer disease (AD) brain has revealed a major defect: in the proteolytic clearance of autophagy substrates. Autophagy failure contributes on several levels to AD pathogenesis and has become an important therapeutic target for AD and other neurodegenerative diseases. We recently observed broad therapeutic effects of stimulating autophagic-lysosomal proteolysis in the TgCRND8 mouse model of AD that exhibits defective proteolytic clearance of autophagic substrates, robust intralysosomal amyloid-beta peptide (Abeta) accumulation, extracellular beta-amyloid deposition and cognitive deficits. By genetically deleting the lysosomal cysteine protease inhibitor, cystatin B (CstB), to selectively restore depressed cathepsin activities, we substantially cleared Abeta, ubiquitinated proteins and other autophagic substrates from autolysosomes/lysosomes and rescued autophagic-lysosomal pathology, as well as reduced total Abeta40/42 levels and extracellular amyloid deposition, highlighting the underappreciated importance of the lysosomal system for Abeta clearance. Most importantly, lysosomal remediation prevented the marked learning and memory deficits in TgCRND8 mice. Our findings underscore the pathogenic significance of autophagic-lysosomal dysfunction in AD and demonstrate the value of reversing this dysfunction as an innovative therapeautic strategy for AD

OBJECTIVE: Hyperuricemia of gout can arise due to either overproduction or underexcretion of uric acid. Not all available urate-lowering therapies are equally effective and safe for use in patients with renal disease. The objective of this post-hoc analysis was to determine the effectiveness of the xanthine oxidase inhibitor febuxostat in reducing serum urate (sUA) levels in gouty patients who were either overproducers or underexcretors. METHODS: Gouty subjects 18 to 85 years of age with sUA >/= 8.0 mg/dl at baseline were enrolled in a Phase 2, 28-day, multicenter, randomized, double-blind, placebo-controlled trial and randomized to receive febuxostat 40 mg, 80 mg, or 120 mg daily, or placebo. The primary efficacy endpoint was the proportion of subjects with sUA < 6.0 mg/dl at Day 28. Secondary efficacy endpoints included percentage reductions in sUA and urinary uric acid (uUA) from baseline to Day 28. RESULTS: Of the 153 subjects, 118 (77%) were underexcretors (uUA </= 800 mg/24 h) and 32 (21%) were overproducers (uUA > 800 mg/24 h); baseline uUA data were missing for 3 subjects. Treatment with febuxostat led to the majority of subjects achieving sUA < 6.0 mg/dl at Day 28. Treatment with any dose of febuxostat led to significantly greater percentage reductions in uUA than that observed in the placebo group, for both underexcretors and overproducers. CONCLUSION: Febuxostat is a highly efficacious urate-lowering therapy in patients with gout regardless of overproduction or underexcretion status

Physical activity is one of the most important determinants of cardiac function. The ability of the heart to increase delivery of oxygen and metabolic fuels relies on an array of adaptive responses necessary to match bodily demand while avoiding exhaustion of cardiac resources. The ATP-sensitive potassium (K(ATP)) channel has the unique ability to adjust cardiac membrane excitability in accordance with ATP and ADP levels, and up-regulation of its expression that occurs in response to exercise could represent a critical element of this adaption. However, the mechanism by which K(ATP) channel expression changes result in a beneficial effect on cardiac excitability and function remains to be established. Here, we demonstrate that an exercise-induced rise in K(ATP) channel expression enhanced the rate and magnitude of action potential shortening in response to heart rate acceleration. This adaptation in membrane excitability promoted significant reduction in cardiac energy consumption under escalating workloads. Genetic disruption of normal K(ATP) channel pore function abolished the exercise-related changes in action potential duration adjustment and caused increased cardiac energy consumption. Thus, an expression-driven enhancement in the K(ATP) channel-dependent membrane response to alterations in cardiac workload represents a previously unrecognized mechanism for adaptation to physical activity and a potential target for cardioprotection

Being gated by high-energy nucleotides, cardiac ATP-sensitive potassium (K(ATP)) channels are exquisitely sensitive to changes in cellular energy metabolism. An emerging view is that proteins associated with the K(ATP) channel provide an additional layer of regulation. Using putative sulfonylurea receptor (SUR) coiled-coil domains as baits in a 2-hybrid screen against a rat cardiac cDNA library, we identified glycolytic enzymes (GAPDH and aldolase A) as putative interacting proteins. Interaction between aldolase and SUR was confirmed using GST pulldown assays and coimmunoprecipitation assays. Mass spectrometry of proteins from K(ATP) channel immunoprecipitates of rat cardiac membranes identified glycolysis as the most enriched biological process. Coimmunoprecipitation assays confirmed interaction for several glycolytic enzymes throughout the glycolytic pathway. Immunocytochemistry colocalized many of these enzymes with K(ATP) channel subunits in rat cardiac myocytes. The catalytic activities of aldolase and pyruvate kinase functionally modulate K(ATP) channels in patch-clamp experiments, whereas d-glucose was without effect. Overall, our data demonstrate close physical association and functional interaction of the glycolytic process (particularly the distal ATP-generating steps) with cardiac K(ATP) channels.-Hong, M., Kefaloyianni, E., Bao, L., Malester, B., Delaroche, D., Neubert, T. A., Coetzee, W. A. Cardiac ATP-sensitive K(+) channel associates with the glycolytic enzyme complex

Inherited retinal degeneration results from many different mutations in either photoreceptor-specific or nonphotoreceptor-specific genes. However, nearly all mutations lead to a common blinding phenotype that initiates with rod cell death, followed by loss of cones. In most retinal degenerations, other retinal neuron cell types survive for long periods after blindness from photoreceptor loss. One strategy to restore light responsiveness to a retina rendered blind by photoreceptor degeneration is to express light-regulated ion channels or transporters in surviving retinal neurons. Recent experiments in rodents have restored light-sensitivity by expressing melanopsin or microbial opsins either broadly throughout the retina or selectively in the inner segments of surviving cones or in bipolar cells. Here, we present an approach whereby a genetically and chemically engineered light-gated ionotropic glutamate receptor (LiGluR) is expressed selectively in retinal ganglion cells (RGCs), the longest-surviving cells in retinal blinding diseases. When expressed in the RGCs of a well-established model of retinal degeneration, the rd1 mouse, LiGluR restores light sensitivity to the RGCs, reinstates light responsiveness to the primary visual cortex, and restores both the pupillary reflex and a natural light-avoidance behavior.

Currently available optogenetic tools, including microbial light-activated ion channels and transporters, are transforming systems neuroscience by enabling precise remote control of neuronal firing, but they tell us little about the role of indigenous ion channels in controlling neuronal function. Here, we employ a chemical-genetic strategy to engineer light sensitivity into several mammalian K(+) channels that have different gating and modulation properties. These channels provide the means for photoregulating diverse electrophysiological functions. Photosensitivity is conferred on a channel by a tethered ligand photoswitch that contains a cysteine-reactive maleimide (M), a photoisomerizable azobenzene (A), and a quaternary ammonium (Q), a K(+) channel pore blocker. Using mutagenesis, we identify the optimal extracellular cysteine attachment site where MAQ conjugation results in pore blockade when the azobenzene moiety is in the trans but not cis configuration. With this strategy, we have conferred photosensitivity on channels containing Kv1.3 subunits (which control axonal action potential repolarization), Kv3.1 subunits (which contribute to rapid-firing properties of brain neurons), Kv7.2 subunits (which underlie "M-current"), and SK2 subunits (which are Ca(2+)-activated K(+) channels that contribute to synaptic responses). These light-regulated channels may be overexpressed in genetically targeted neurons or substituted for native channels with gene knockin technology to enable precise optopharmacological manipulation of channel function.

Although the central noradrenergic system has been shown to be involved in a number of behavioral and neurophysiological processes, the relation of these to its role in depressive illness has been difficult to define. The present review discusses the hypothesis that one of its chief functions that may be related to affective illness is the inhibition of behavioral activation, a prominent symptom of the disorder. This hypothesis is found to be consistent with most previous neuropsychopharmacological and immunohistochemical experiments on active behavior in rodents in a variety of experimental conditions using manipulation of neurotransmission at both locus coeruleus and forebrain adrenergic receptors. The findings support a mechanism in which high rates of noradrenergic neural activity suppress the neural activity of principal neurons in forebrain regions mediating active behavior. The suppression may be mediated through postsynaptic galaninergic and adrenergic receptors, and via the release of corticotrophin-releasing hormone. The hypothesis is consistent with clinical evidence for central noradrenergic system hyperactivity in depressives and with the view that this hyperactivity is a contributing etiological factor in the disorder. A similar mechanism may underlie the ability of the noradrenergic system to suppress seizure activity suggesting that inhibition of the spread of neural activation may be a unifying function

Functional connectivity between the piriform cortex and limbic and neocortical areas was assessed using functional magnetic resonance imaging (fMRI) of urethane anesthetized rats that spontaneously cycled between slow-wave and fast-wave states. Slow-wave and fast-wave states were determined indirectly through monitoring of respiration rate, which was confirmed to co-vary with state as determined by electrophysiological recordings. Previous electrophysiological data have suggested that the piriform cortex shifts between responsiveness to afferent odor input during fast-wave states and enhanced functional connectivity with limbic areas during slow-wave state. The present results demonstrate that fMRI-based resting state functional connectivity between the piriform cortex and both limbic and neocortical areas is enhanced during slow-wave state compared to fast-wave state using respiration as an indirect measure of state in urethane anesthetized rats. This state-dependent shift in functional connectivity may be important for sleep-dependent odor memory consolidation

Defining the neural and neurochemical substrates of response inhibition is of crucial importance for the study and treatment of pathologies characterized by impulsivity such as attention-deficit/hyperactivity disorder and addiction. The stop-signal task (SST) is one of the most popular paradigms used to study the speed and efficacy of inhibitory processes in humans and other animals. Here we investigated the effect of temporarily inactivating different prefrontal subregions in the rat by means of muscimol microinfusions on SST performance. We found that dorsomedial prefrontal cortical areas are important for inhibiting an already initiated response. We also investigated the possible neural substrates of the selective noradrenaline reuptake inhibitor atomoxetine via its local microinfusion into different subregions of the rat prefrontal cortex. Our results show that both orbitofrontal and dorsal prelimbic cortices mediate the beneficial effects of atomoxetine on SST performance. To assess the neurochemical specificity of these effects, we infused the alpha2-adrenergic agonist guanfacine and the D(1)/D(2) antagonist alpha-flupenthixol in dorsal prelimbic cortex to interfere with noradrenergic and dopaminergic neurotransmission, respectively. Guanfacine, which modulates noradrenergic neurotransmission, selectively impaired stopping, whereas blocking dopaminergic receptors by alpha-flupenthixol infusion prolonged go reaction time only, confirming the important role of noradrenergic neurotransmission in response inhibition. These results show that, similar to humans, distinct networks play important roles during SST performance in the rat and that they are differentially modulated by noradrenergic and dopaminergic neurotransmission. This study advances our understanding of the neuroanatomical and neurochemical determinants of impulsivity, which are relevant for a range of psychiatric disorders.