Functional properties and projections of neurons in the medial amygdala

The medial nucleus of the amygdala (MeA) plays a key role in innate emotional behaviors by relaying olfactory information to hypothalamic nuclei involved in reproduction and defense. However, little is known about the neuronal components of this region or their role in the olfactory-processing circuitry of the amygdala. Here, we have characterized neurons in the posteroventral division of the medial amygdala (MePV) using the GAD67-GFP mouse. Based on their electrophysiological properties and GABA expression, unsupervised cluster analysis divided MePV neurons into three types of GABAergic (Types 1-3) and two non-GABAergic cells (Types I and II). All cell types received olfactory synaptic input from the accessory olfactory bulb and, with the exception of Type 2 GABAergic neurons, sent projections to both reproductive and defensive hypothalamic nuclei. Type 2 GABAergic cells formed a chemically and electrically interconnected network of local circuit inhibitory interneurons that resembled neurogliaform cells of the piriform cortex and provided feedforward inhibition of the olfactory-processing circuitry of the MeA. These findings provide a description of the cellular organization and connectivity of the MePV and further our understanding of amygdala circuits involved in olfactory processing and innate emotions

A Specific class of interneuron mediates inhibitory plasticity in the lateral amygdala

The lateral amygdala (LA) plays a key role in emotional learning and is the main site for sensory input into the amygdala. Within the LA, pyramidal neurons comprise the major cell population with plasticity of inputs to these neurons thought to underlie fear learning. Pyramidal neuron activity is tightly controlled by local interneurons, and GABAergic modulation strongly influences amygdala-dependent learning. Synaptic inputs to some interneurons in the LA can also undergo synaptic plasticity, but the identity of these cells and the mechanisms that underlie this plasticity are not known. Here we show that long-term potentiation (LTP) in LA interneurons is restricted to a specific type of interneuron that is defined by the lack of expression of synaptic NR2B subunits. We find that LTP is only present at cortical inputs to these cells and is initiated by calcium influx via calcium-permeable AMPA receptors. LTP is maintained by trafficking of GluR2-lacking AMPA receptors that require an interaction with SAP97 and the actin cytoskeleton. Our results define a novel population of interneurons in the LA that control principal neuron excitability by feed-forward inhibition of cortical origin. This selective enhanced inhibition may contribute to reducing the activity of principal neurons engaged during extinction of conditioned fear

Prefrontal and auditory input to intercalated neurons of the Amygdala

The basolateral amygdala (BLA) and prefrontal cortex (PFC) are partners in fear learning and extinction. Intercalated (ITC) cells are inhibitory neurons that surround the BLA. Lateral ITC (IITC) neurons provide feed-forward inhibition to BLA principal neurons, whereas medial ITC (mITC) neurons form an inhibitory interface between the BLA and central amygdala (CeA). Notably, infralimbic prefrontal (IL) input to mITC neurons is thought to play a key role in fear extinction. Here, using targeted optogenetic stimulation, we show that IITC neurons receive auditory input from cortical and thalamic regions. IL inputs innervate principal neurons in the BLA but not mITC neurons. These results suggest that (1) these neurons may play a more central role in fear learning as both IITCs and mITCs receive auditory input and that (2) mITC neurons cannot be driven directly by the IL, and their role in fear extinction is likely mediated via the BLA

Schizophrenia and the progression of emotional expression in relation to others

Gaining an improved understanding of people diagnosed with schizophrenia has the potential to influence priorities for therapy. Psychosis is commonly understood through the perspective of the medical model. However, the experience of social context surrounding psychosis is not well understood. In this research project we used a phenomenological methodology with a longitudinal design to interview 7 participants across a 12-month period to understand the social experiences surrounding psychosis. Eleven themes were explicated and divided into two phases of the illness experience: (a) transition into emotional shutdown included the experiences of not being acknowledged, relational confusion, not being expressive, detachment, reliving the past, and having no sense of direction; and (b) recovery from emotional shutdown included the experiences of being acknowledged, expression, resolution, independence, and a sense of direction. The experiential themes provide clinicians with new insights to better assess vulnerability, and have the potential to inform goals for therapy

Immature doublecortin-positive hippocampal neurons are important for learning but not for remembering

It is now widely accepted that hippocampal neurogenesis underpins critical cognitive functions, such as learning and memory. To assess the behavioral importance of adult-born neurons, we developed a novel knock-in mouse model that allowed us to specifically and reversibly ablate hippocampal neurons at an immature stage. In these mice, the diphtheria toxin receptor (DTR) is expressed under control of the doublecortin (DCX) promoter, which allows for specific ablation of immature DCX-expressing neurons after administration of diphtheria toxin while leaving the neural precursor pool intact. Using a spatially challenging behavioral test (a modified version of the active place avoidance test), we present direct evidence that immature DCX-expressing neurons are required for successful acquisition of spatial learning, as well as reversal learning, but are not necessary for the retrieval of stored long-term memories. Importantly, the observed learning deficits were rescued as newly generated immature neurons repopulated the granule cell layer upon termination of the toxin treatment. Repeat (or cyclic) depletion of immature neurons reinstated behavioral deficits if the mice were challenged with a novel task. Together, these findings highlight the potential of stimulating neurogenesis as a means to enhance learning

Airborne characterization of smoke marker ratios from prescribed burning

A Particle-Into-Liquid Sampler – Total Organic Carbon (PILS-TOC) and fraction collector system was flown aboard a Twin Otter aircraft sampling prescribed burning emissions in South Carolina in November 2011 to obtain smoke marker measurements. The fraction collector provided 2 min time-integrated offline samples for carbohydrate (i.e., smoke markers levoglucosan, mannosan, and galactosan) analysis by high-performance anion-exchange chromatography with pulsed amperometric detection. Each fire location appeared to have a unique 1levoglucosan /1water-soluble organic carbon (WSOC) ratio (RF01/RF02/RF03/RF05 = 0.163± 0.007 μg C μg−1 C, RF08 = 0.115 ± 0.011 μg C μg−1 C, RF09A = 0.072 ± 0.028 μgC μg−1 C, and RF09B = 0.042 ± 0.008 μg Cμg−1 C, where RF means research flight). These ratios were comparable to those obtained from controlled laboratory burns and suggested that the emissions sampled during RF01/F02/RF03/RF05 were dominated by the burning of grasses, RF08 by leaves, RF09A by needles, and RF09B by marsh grasses. These findings were further supported by the 1galactosan /1levoglucosan ratios (RF01/RF02/RF03/RF05 = 0.067 ± 0.004 μg μg−1, RF08 = 0.085 ± 0.009 μg μg−1, and RF09A = 0.101 ± 0.029 μg μg−1) obtained as well as by the ground-based fuel and filter sample analyses during RF01/RF02/RF03/RF05. Differences between 1potassium /1levoglucosan ratios obtained for these prescribed fires vs. laboratory-scale measurements suggest that some laboratory burns may not accurately represent potassium emissions from prescribed burns. The1levoglucosan /1WSOC ratio had no clear dependence on smoke age or fire dynamics suggesting that this ratio is more dependent on the type of fuel being burned. Levoglucosan was stable over a timescale of at least 1.5 h and could be useful to help estimate the air quality impacts of biomass burning

Methane Emissions from Process Equipment at Natural Gas Production Sites in the United States: Liquid Unloadings

Methane emissions from liquid unloadings were measured at 107 wells in natural gas production regions throughout the United States. Liquid unloadings clear wells of accumulated liquids to increase production, employing a variety of liquid lifting mechanisms. In this work, wells with and without plunger lifts were sampled. Most wells without plunger lifts unload less than 10 times per year with emissions averaging 21 000–35 000 scf methane (0.4–0.7 Mg) per event (95% confidence limits of 10 000–50 000 scf/event). For wells with plunger lifts, emissions averaged 1000–10 000 scf methane (0.02–0.2 Mg) per event (95% confidence limits of 500–12 000 scf/event). Some wells with plunger lifts are automatically triggered and unload thousands of times per year and these wells account for the majority of the emissions from all wells with liquid unloadings. If the data collected in this work are assumed to be representative of national populations, the data suggest that the central estimate of emissions from unloadings (270 Gg/yr, 95% confidence range of 190–400 Gg) are within a few percent of the emissions estimated in the EPA 2012 Greenhouse Gas National Emission Inventory (released in 2014), with emissions dominated by wells with high frequencies of unloadings

North Carolina macular dystrophy (MCDR1) caused by a novel tandem duplication of the PRDM13 gene

PURPOSE: To identify the underlying cause of disease in a large family with North Carolina macular dystrophy (NCMD). METHODS: A large four-generation family (RFS355) with an autosomal dominant form of NCMD was ascertained. Family members underwent comprehensive visual function evaluations. Blood or saliva from six affected family members and three unaffected spouses was collected and DNA tested for linkage to the MCDR1 locus on chromosome 6q12. Three affected family members and two unaffected spouses underwent whole exome sequencing (WES) and subsequently, custom capture of the linkage region followed by next-generation sequencing (NGS). Standard PCR and dideoxy sequencing were used to further characterize the mutation. RESULTS: Of the 12 eyes examined in six affected individuals, all but two had Gass grade 3 macular degeneration features. Large central excavation of the retinal and choroid layers, referred to as a macular caldera, was seen in an age-independent manner in the grade 3 eyes. The calderas are unique to affected individuals with MCDR1. Genome-wide linkage mapping and haplotype analysis of markers from the chromosome 6q region were consistent with linkage to the MCDR1 locus. Whole exome sequencing and custom-capture NGS failed to reveal any rare coding variants segregating with the phenotype. Analysis of the custom-capture NGS sequencing data for copy number variants uncovered a tandem duplication of approximately 60 kb on chromosome 6q. This region contains two genes, CCNC and PRDM13. The duplication creates a partial copy of CCNC and a complete copy of PRDM13. The duplication was found in all affected members of the family and is not present in any unaffected members. The duplication was not seen in 200 ethnically matched normal chromosomes. CONCLUSIONS: The cause of disease in the original family with MCDR1 and several others has been recently reported to be dysregulation of the PRDM13 gene, caused by either single base substitutions in a DNase 1 hypersensitive site upstream of the CCNC and PRDM13 genes or a tandem duplication of the PRDM13 gene. The duplication found in the RFS355 family is distinct from the previously reported duplication and provides additional support that dysregulation of PRDM13, not CCNC, is the cause of NCMD mapped to the MCDR1 locus

Paradoxical enhancement of fear extinction memory and synaptic plasticity by inhibition of the histone acetyltransferase p300

It is well established that the coordinated regulation of activity-dependent gene expression by the histone acetyltransferase (HAT) family of transcriptional coactivators is crucial for the formation of contextual fear and spatial memory, and for hippocampal synaptic plasticity. However, no studies have examined the role of this epigenetic mechanism within the infralimbic prefrontal cortex (ILPFC), an area of the brain that is essential for the formation and consolidation of fear extinction memory. Here we report that a postextinction training infusion of a combined p300/CBP inhibitor (Lys-CoA-Tat), directly into the ILPFC, enhances fear extinction memory in mice. Our results also demonstrate that the HAT p300 is highly expressed within pyramidal neurons of the ILPFC and that the small-molecule p300-specific inhibitor (C646) infused into the ILPFC immediately after weak extinction training enhances the consolidation of fear extinction memory. C646 infused 6 h after extinction had no effect on fear extinction memory, nor did an immediate postextinction training infusion into the prelimbic prefrontal cortex. Consistent with the behavioral findings, inhibition of p300 activity within the ILPFC facilitated long-term potentiation (LTP) under stimulation conditions that do not evoke long-lasting LTP. These data suggest that one function of p300 activity within the ILPFC is to constrain synaptic plasticity, and that a reduction in the function of this HAT is required for the formation of fear extinction memory

Phosphorylation of GFAP is associated with injury in the neonatal pig hypoxic-ischemic brain

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein expressed in the astrocyte cytoskeleton that plays an important role in the structure and function of the cell. GFAP can be phosphorylated at six serine (Ser) or threonine (Thr) residues but little is known about the role of GFAP phosphorylation in physiological and pathophysiological states. We have generated antibodies against two phosphorylated GFAP (pGFAP) proteins: p8GFAP, where GFAP is phosphorylated at Ser-8 and p13GFAP, where GFAP is phosphorylated at Ser-13. We examined p8GFAP and p13GFAP expression in the control neonatal pig brain and at 24 and 72 h after an hypoxic-ischemic (HI) insult. Immunohistochemistry demonstrated pGFAP expression in astrocytes with an atypical cytoskeletal morphology, even in control brains. Semi-quantitative western blotting revealed that p8GFAP expression was significantly increased at 24 h post-insult in HI animals with seizures in frontal, parietal, temporal and occipital cortices. At 72 h post-insult, p8GFAP and p13GFAP expression were significantly increased in HI animals with seizures in brain regions that are vulnerable to cellular damage (cortex and basal ganglia), but no changes were observed in brain regions that are relatively spared following an HI insult (brain stem and cerebellum). Increased pGFAP expression was associated with poor neurological outcomes such as abnormal encephalography and neurobehaviour, and increased histological brain damage. Phosphorylation of GFAP may play an important role in astrocyte remodelling during development and disease and could potentially contribute to the plasticity of the central nervous system