Locus Coeruleus Activation Patterns Differentially Modulate Odor Discrimination Learning and Odor Valence in Rats.

The locus coeruleus (LC) produces phasic and tonic firing patterns that are theorized to have distinct functional consequences. However, how different firing modes affect learning and valence encoding of sensory information are unknown. Here, we show bilateral optogenetic activation of rat LC neurons using 10-Hz phasic trains of either 300 ms or 10 s accelerated acquisition of a similar odor discrimination. Similar odor discrimination learning was impaired by noradrenergic blockade in the piriform cortex (PC). However, 10-Hz phasic light-mediated learning facilitation was prevented by a dopaminergic antagonist in the PC, or by ventral tegmental area (VTA) silencing with lidocaine, suggesting a LC-VTA-PC dopamine circuitry involvement. Ten-hertz tonic stimulation did not alter odor discrimination acquisition, and was ineffective in activating VTA DA neurons. For valence encoding, tonic stimulation at 25 Hz induced conditioned odor aversion, whereas 10-Hz phasic stimulations produced an odor preference. Both conditionings were prevented by noradrenergic blockade in the basolateral amygdala (BLA). Cholera Toxin B retro-labeling showed larger engagement of nucleus accumbens-projecting neurons in the BLA with 10-Hz phasic activation, and larger engagement of central amygdala projecting cells with 25-Hz tonic light. These outcomes argue that the LC activation patterns differentially influence both target networks and behavior.

Novelty-like activation of locus coeruleus protects against deleterious human pretangle tau effects while stress-inducing activation worsens its effects.

The earliest abnormality associated with Alzheimer's disease (AD) is the presence of persistently phosphorylated pretangle tau in locus coeruleus (LC) neurons. LC neuron numbers and fiber density are positive predictors of cognition prior to death. Using an animal model of LC pretangle tau, we ask if LC activity patterns influence the sequelae of pretangle tau. We seeded LC neurons with a pretangle human tau gene. We provided daily novelty- or stress-associated optogenetic activation patterns to LC neurons for 6 weeks in mid-adulthood and, subsequently, probed cognitive and anatomical changes. Prior LC phasic stimulation prevented spatial and olfactory discrimination deficits and preserved LC axonal density. A stress-associated activation pattern increased indices of anxiety and depression, did not improve cognition, and worsened LC neuronal health. These results argue that variations in environmental experiences associated with differing LC activity patterns may account for individual susceptibility to development of AD in humans.

Atomoxetine Does Not Improve Complex Attention in Idiopathic Parkinson's Disease Patients with Cognitive Deficits: A Meta-Analysis.

OBJECTIVES: To evaluate the effects of atomoxetine on complex attention and other neurocognitive domains in idiopathic Parkinson's disease (PD). METHODS: Interventional trials reporting changes in complex attention and other neurocognitive functions (Diagnostic and Statistical Manual of Mental Disorders-5) following administration of atomoxetine for at least 8 weeks in adults with idiopathic PD were included. Effect sizes (Cohen's d), the standardized mean difference in the scores of each cognitive domain, were compared using a random-effects model (MetaXL version 5.3). RESULTS: Three studies were included in the final analysis. For a change in complex attention in PD with mild cognitive impairment (MCI), the estimated effect size was small and nonsignificant (0.16 (95% CI: -0.09, 0.42), n = 42). For changes in executive function, perceptual-motor function, language, social cognition, and learning and memory, the estimated effect sizes were small and medium, but nonsignificant. A deteriorative trend in executive function was observed after atomoxetine treatment in PD with MCI. For a change in global cognitive function in PD without MCI, the estimated effect size was large and significant. CONCLUSION: In idiopathic PD with MCI, atomoxetine does not improve complex attention. Also, a deteriorative trend in the executive function was noted.

Shared Pheromonal Communication of Specific Fear Between Adult Sprague Dawley Rats.

Rats are highly social animals, and mainly communicate with one another in two ways: through ultrasonic vocalizations and pheromones. Most research on pheromones has been dedicated those regarding sexual behavior, but more recently pheromones which signal danger to conspecifics have been identified in rodents. In fact, rats are capable of communicating information regarding a specific fear to a companion with which they share a cage. If a rat is trained to associate a previously neutral odor with a foot shock and then pair housed with another rat, the companion will also display a fear response specific to the trained odor, despite never being shocked itself. This communication relies on pheromones; presenting soiled bedding from a shocked rat to an individually housed naïve rat produces the same fear response in the naïve rat. The current protocol describes how to produce this phenomenon in adult Sprague Dawley rats. It is simple and easily reproduced, requires minimal equipment, and may be completed within one week.

Novel cortex lytic enzymes in Bacillus megaterium QM B1551 spores.

Present models for spore germination in Bacillus species include a requirement for either the SleB or CwlJ cortex lytic enzymes to efficiently depolymerise the spore cortex. Previous work has demonstrated that B. megaterium spores may differ to other species in this regard, since sleB cwlJ null mutant spores complemented with the gene in trans for the non-peptidoglycan lysin YpeB can efficiently degrade the cortex. Here, we identify two novel cortex lytic enzymes, encoded at the BMQ_2391 and BMQ_3234 loci, which are essential for cortex hydrolysis in the absence of SleB and CwlJ. Ellipsoid localisation microscopy places the BMQ_3234 protein within the inner-spore coat, a region of the spore that is populated by other cortex lytic enzymes. The findings reinforce the idea that there is a degree of variation in mechanisms of cortex hydrolysis across the Bacillales, raising potential implications for environmental decontamination strategies based upon targeted inactivation of components of the spore germination apparatus.

An experimental model of Braak's pretangle proposal for the origin of Alzheimer's disease: the role of locus coeruleus in early symptom development.

BACKGROUND: The earliest brain pathology related to Alzheimer's disease (AD) is hyperphosphorylated soluble tau in the noradrenergic locus coeruleus (LC) neurons. Braak characterizes five pretangle tau stages preceding AD tangles. Pretangles begin in young humans and persist in the LC while spreading from there to other neuromodulatory neurons and, later, to the cortex. While LC pretangles appear in all by age 40, they do not necessarily result in AD prior to death. However, with age and pretangle spread, more individuals progress to AD stages. LC neurons are lost late, at Braak stages III-IV, when memory deficits appear. It is not clear if LC hyperphosphorylated tau generates the pathology and cognitive changes associated with preclinical AD. We use a rat model expressing pseudohyperphosphorylated human tau in LC to investigate the hypothesis that LC pretangles generate preclinical Alzheimer pathology. METHODS: We infused an adeno-associated viral vector carrying a human tau gene pseudophosphorylated at 14 sites common in LC pretangles into 2-3- or 14-16-month TH-Cre rats. We used odor discrimination to probe LC dysfunction, and we evaluated LC cell and fiber loss. RESULTS: Abnormal human tau was expressed in LC and exhibited somatodendritic mislocalization. In rats infused at 2-3 months old, 4 months post-infusion abnormal LC tau had transferred to the serotonergic raphe neurons. After 7 months, difficult similar odor discrimination learning was impaired. Impairment was associated with reduced LC axonal density in the olfactory cortex and upregulated ß1-adrenoceptors. LC infusions in 14-16-month-old rats resulted in more severe outcomes. By 5-6 months post-infusion, rats were impaired even in simple odor discrimination learning. LC neuron number was reduced. Human tau appeared in the microglia and cortical neurons. CONCLUSIONS: Our animal model suggests, for the first time, that Braak's hypothesis that human AD originates with pretangle stages is plausible. LC pretangle progression here generates both preclinical AD pathological changes and cognitive decline. The odor discrimination deficits are similar to human odor identification deficits seen with aging and preclinical AD. When initiated in aged rats, pretangle stages progress rapidly and cause LC cell loss. These age-related outcomes are associated with a severe learning impairment consistent with memory decline in Braak stages III-IV.

Pheromone-Induced Odor Associative Fear Learning in Rats.

Alarm pheromones alert conspecifics to the presence of danger. Can pheromone communication aid in learning specific cues? Such facilitation has an evident evolutionary advantage. We use two associative learning paradigms to test this hypothesis. The first is stressed cage mate-induced conditioning. One pair-housed adult rat received 4 pairings of terpinene + shock over 30 min. Ten minutes after return to the home cage, its companion rat was removed and exposed to terpinene. Single-housed controls were exposed to either terpinene or shock only. Companion rats showed terpinene-specific freezing, which was prevented by ß-adrenoceptor blockade. Using Arc to index neuronal activation in response to terpinene re-exposure, stressed cage-mate induced associative learning was measured. Companion rats showed increased neuronal activity in the accessory olfactory bulb, while terpinene + shock-conditioned rats showed increased activity in the main olfactory bulb. Both groups had enhanced activity in the anterior basolateral amygdala and central amygdala. To test involvement of pheromone mediation, in the 2nd paradigm, we paired terpinene with soiled bedding from odor + shock rats or a rat alarm pheromone. Both conditioning increased rats' freezing to terpinene. Blocking NMDA receptors in the basolateral amygdala prevented odor-specific learning suggesting shock and pheromone-paired pathways converge in the amygdala. An alarm pheromone thus enables cue-specific learning as well as signalling danger.

Orthologues of Bacillus subtilis Spore Crust Proteins Have a Structural Role in the Bacillus megaterium QM B1551 Spore Exosporium.

The exosporium of Bacillus megaterium QM B1551 spores is morphologically distinct from exosporia observed for the spores of many other species. Previous work has demonstrated that unidentified genes carried on one of the large indigenous plasmids are required for the assembly of the Bacillus megaterium exosporium. Here, we provide evidence that pBM600-encoded orthologues of the Bacillus subtilis CotW and CotX proteins, which form the crust layer in spores of that species, are structural components of the Bacillus megaterium QM B1551 spore exosporium. The introduction of plasmid-borne cotW and orthologous cotX genes to the PV361 strain, which lacks all indigenous plasmids and produces spores that are devoid of an exosporium, results in the development of spores with a rudimentary exosporium-type structure. Additionally, purified recombinant CotW protein is shown to assemble at the air-water interface to form thin sheets of material, which is consistent with the idea that this protein may form a basal layer in the Bacillus megaterium QM B1551 exosporium.IMPORTANCE When starved of nutrients, some bacterial species develop metabolically dormant spores that can persist in a viable state in the environment for several years. The outermost layers of spores are of particular interest since (i) these represent the primary site for interaction with the environment and (ii) the protein constituents may have biotechnological applications. The outermost layer, or exosporium, in Bacillus megaterium QM B1551 spores is of interest, as it is morphologically distinct from the exosporia of spores of the pathogenic Bacillus cereus family. In this work, we provide evidence that structurally important protein constituents of the Bacillus megaterium exosporium are different from those in the Bacillus cereus family. We also show that one of these proteins, when purified, can assemble to form sheets of exosporium-like material. This is significant, as it indicates that spore-forming bacteria employ different proteins and mechanisms of assembly to construct their external layers.

Proteins Encoded by the gerP Operon Are Localized to the Inner Coat in Bacillus cereus Spores and Are Dependent on GerPA and SafA for Assembly.

The germination of Bacillus spores is triggered by certain amino acids and sugar molecules which permeate the outermost layers of the spore to interact with receptor complexes that reside in the inner membrane. Previous studies have shown that mutations in the hexacistronic gerP locus reduce the rate of spore germination, with experimental evidence indicating that the defect stems from reduced permeability of the spore coat to germinant molecules. Here, we use the ellipsoid localization microscopy technique to reveal that all six Bacillus cereus GerP proteins share proximity with cortex-lytic enzymes within the inner coat. We also reveal that the GerPA protein alone can localize in the absence of all other GerP proteins and that it has an essential role for the localization of all other GerP proteins within the spore. Its essential role is also demonstrated to be dependent on SafA, but not CotE, for localization, which is consistent with an inner coat location. GerP-null spores are shown also to have reduced permeability to fluorescently labeled dextran molecules compared to wild-type spores. Overall, the results support the hypothesis that the GerP proteins have a structural role within the spore associated with coat permeability.IMPORTANCE The bacterial spore coat comprises a multilayered proteinaceous structure that influences the distribution, survival, and germination properties of spores in the environment. The results from the current study are significant since they increase our understanding of coat assembly and architecture while adding detail to existing models of germination. We demonstrate also that the ellipsoid localization microscopy (ELM) image analysis technique can be used as a novel tool to provide direct quantitative measurements of spore coat permeability. Progress in all of these areas should ultimately facilitate improved methods of spore control in a range of industrial, health care, and environmental sectors.

ß-Adrenoceptor activation enhances L-type calcium channel currents in anterior piriform cortex pyramidal cells of neonatal mice: implication for odor learning.

Early odor preference learning occurs in one-week-old rodents when a novel odor is paired with a tactile stimulation mimicking maternal care. ß-Adrenoceptors and L-type calcium channels (LTCCs) in the anterior piriform cortex (aPC) are critically involved in this learning. However, whether ß-adrenoceptors interact directly with LTCCs in aPC pyramidal cells is unknown. Here we show that pyramidal cells expressed significant LTCC currents that declined with age. ß-Adrenoceptor activation via isoproterenol age-dependently enhanced LTCC currents. Nifedipine-sensitive, isoproterenol enhancement of calcium currents was only observed in post-natal day 7-10 mice. APC ß-adrenoceptor activation induced early odor preference learning was blocked by nifedipine coinfusion.

The Role of L-type Calcium Channels in Olfactory Learning and Its Modulation by Norepinephrine.

L type calcium channels (LTCCs) are prevalent in different systems and hold immense importance for maintaining/performing selective functions. In the nervous system, CaV1.2 and CaV1.3 are emerging as critical modulators of neuronal functions. Although the general role of these calcium channels in modulating synaptic plasticity and memory has been explored, their role in olfactory learning is not well understood. In this review article we first discuss the role of LTCCs in olfactory learning especially focusing on early odor preference learning in neonate rodents, presenting evidence that while NMDARs initiate stimulus-specific learning, LTCCs promote protein-synthesis dependent long-term memory (LTM). Norepinephrine (NE) release from the locus coeruleus (LC) is essential for early olfactory learning, thus noradrenergic modulation of LTCC function and its implication in olfactory learning is discussed here. We then address the differential roles of LTCCs in adult learning and learning in aged animals.

SpoVT: From Fine-Tuning Regulator in Bacillus subtilis to Essential Sporulation Protein in Bacillus cereus.

Sporulation is a highly sophisticated developmental process adopted by most Bacilli as a survival strategy to withstand extreme conditions that normally do not support microbial growth. A complicated regulatory cascade, divided into various stages and taking place in two different compartments of the cell, involves a number of primary and secondary regulator proteins that drive gene expression directed toward the formation and maturation of an endospore. Such regulator proteins are highly conserved among various spore formers. Despite this conservation, both regulatory and phenotypic differences are observed between different species of spore forming bacteria. In this study, we demonstrate that deletion of the regulatory sporulation protein SpoVT results in a severe sporulation defect in Bacillus cereus, whereas this is not observed in Bacillus subtilis. Although spores are initially formed, the process is stalled at a later stage in development, followed by lysis of the forespore and the mother cell. A transcriptomic investigation of B. cereus ΔspoVT shows upregulation of genes involved in germination, potentially leading to premature lysis of prespores formed. Additionally, extreme variation in the expression of species-specific genes of unknown function was observed. Introduction of the B. subtilis SpoVT protein could partly restore the sporulation defect in the B. cereus spoVT mutant strain. The difference in phenotype is thus more than likely explained by differences in promoter targets rather than differences in mode of action of the conserved SpoVT regulator protein. This study stresses that evolutionary variances in regulon members of sporulation regulators can have profound effects on the spore developmental process and that mere protein homology is not a foolproof predictor of similar phenotypes.

Norepinephrine Modulates Pyramidal Cell Synaptic Properties in the Anterior Piriform Cortex of Mice: Age-Dependent Effects of ß-adrenoceptors.

Early odor preference learning in rodents occurs within a sensitive period [≤postnatal day (P)10-12], during which pups show a heightened ability to form an odor preference when a novel odor is paired with a tactile stimulation (e.g., stroking). Norepinephrine (NE) release from the locus coeruleus during stroking mediates this learning. However, in older pups, stroking loses its ability to induce learning. The cellular and circuitry mechanisms underpinning the sensitive period for odor preference learning is not well understood. We first established the sensitive period learning model in mice - odor paired with stroking induced odor preference in P8 but not P14 mice. This learning was dependent on NE-ß-adrenoceptors as it was prevented by propranolol injection prior to training. We then tested whether there are developmental changes in pyramidal cell excitability and NE responsiveness in the anterior piriform cortex (aPC) in mouse pups. Although significant differences of pyramidal cell intrinsic properties were found in two age groups (P8-11 and P14+), NE at two concentrations (0.1 and 10 µM) did not alter intrinsic properties in either group. In contrast, in P8-11 pups, NE at 0.1 µM presynaptically decreased miniature IPSC and increased miniature EPSC frequencies. These effects were reversed with a higher dose of NE (10 µM), suggesting involvement of different adrenoceptor subtypes. In P14+ pups, NE at higher doses (1 and 10 µM) acted both pre- and postsynaptically to promote inhibition. These results suggest that enhanced synaptic excitation and reduced inhibition by NE in the aPC network may underlie the sensitive period.

Differential alterations in the expression of neurotransmitter receptors in inner retina following loss of photoreceptors in rd1 mouse.

Loss of photoreceptors leads to significant remodeling in inner retina of rd1 mouse, a widely used model of retinal degeneration. Several morphological and physiological alterations occur in the second- and third-order retinal neurons. Synaptic activity in the excitatory bipolar cells and the predominantly inhibitory amacrine cells is enhanced. Retinal ganglion cells (RGCs) exhibit hyperactivity and aberrant spiking pattern, which adversely affects the quality of signals they can carry to the brain. To further understand the pathophysiology of retinal degeneration, and how it may lead to aberrant spiking in RGCs, we asked how loss of photoreceptors affects some of the neurotransmitter receptors in rd1 mouse. Using Western blotting, we measured the levels of several neurotransmitter receptors in adult rd1 mouse retina. We found significantly higher levels of AMPA, glycine and GABAa receptors, but lower levels of GABAc receptors in rd1 mouse than in wild-type. Since GABAa receptor is expressed in several retinal layers, we employed quantitative immunohistochemistry to measure GABAa receptor levels in specific retinal layers. We found that the levels of GABAa receptors in inner plexiform layer of wild-type and rd1 mice were similar, whereas those in outer plexiform layer and inner nuclear layer combined were higher in rd1 mouse. Specifically, we found that the number of GABAa-immunoreactive somas in the inner nuclear layer of rd1 mouse retina was significantly higher than in wild-type. These findings provide further insights into neurochemical remodeling in the inner retina of rd1 mouse, and how it might lead to oscillatory activity in RGCs.

Oral aripiprazole-induced severe hypoglycemia.

This case report highlights a very rare adverse drug reaction caused by oral aripiprazole resulting in severe hypoglycemia. A 72-year-old-male patient suffering from Parkinson disease on prolonged carbidopa plus levodopa combination therapy (carbidopa 25 mg plus levodopa 100 mg, thrice daily) for 1.3 years was recently diagnosed with psychosis and was initiated 10 mg/day oral aripiprazole. After 10 days of aripiprazole therapy, the patient experienced symptoms of hypoglycemia and on the 21st day, he was hospitalized for severe hypoglycemia. Other long-term concomitant medications taken by this patient were oral losartan (25 mg/day) and rosuvastatin (40 mg/day). Dechallenge and rechallenge with aripiprazole revealed that there is a "definite" (according to Naranjo adverse drug reaction probability scale) relationship between administration of aripiprazole and onset of hypoglycemic events.

Oral pantoprazole-induced acute pancreatitis in an 11-year-old child.

This case report highlights a very rare adverse drug reaction caused by oral pantoprazole resulting in acute pancreatitis. An 11-year-old boy was diagnosed with gastroesophageal reflux disease. Apart from general advice for lifestyle and dietary changes, he was symptomatically prescribed oral pantoprazole 40 mg once daily 30 minutes before meals for 4 weeks. The symptoms of gastroesophageal reflux disease were improving gradually, but the patient developed progressive symptoms of acute pancreatitis and was admitted in the emergency department with acute abdominal pain. Relevant investigations were done, and it was diagnosed as a case of acute pancreatitis. There was no evidence of any other possible hereditary, traumatic, surgical, metabolic, infective, organic, or pathologic causes giving rise to this condition, and this acute pancreatitis was probably drug (pantoprazole) induced. Dechallenge was done, and the patient was treated conservatively resulting in reversal of the diseased state. Naranjo adverse drug reaction probability scale suggested that the likelihood that oral administration of pantoprazole was responsible for the acute pancreatitis was 'probable.'