Catecholaminergic Innervation Research Articles

Chronic intermittent hypoxia remodels catecholaminergic nerve innervation in mouse atria.

Chronic intermittent hypoxia (CIH, a model for sleep apnoea) is a major risk factor for several cardiovascular diseases. Autonomic imbalance (sympathetic overactivity and parasympathetic withdrawal) has emerged as a causal contributor of CIH-induced cardiovascular disease. Previously, we showed that CIH remodels the parasympathetic pathway. However, whether CIH induces remodelling of the cardiac sympathetic innervation remains unknown. Mice (male, C57BL/6J, 2-3months) were exposed to either room air (RA, 21% O2 ) or CIH (alternating 21% and 5.7% O2 , every 6min, 10 hday-1 ) for 8-10weeks. Flat-mounts of their left and right atria were immunohistochemically labelled for tyrosine hydroxylase (TH, a sympathetic marker). Using a confocal microscope (or fluorescence microscope) and Neurlocudia 360digitization and tracing system, we scanned both the left and right atria and quantitatively analysed the sympathetic axon density in both groups. The segmentation data was mapped onto a 3D mouse heart scaffold. Our findings indicated that CIH significantly remodelled the TH immunoreactive (-IR) innervation of the atria by increasing its density at the sinoatrial node, the auricles and the major veins attached to the atria (P < 0.05, n=7). Additionally, CIH increased the branching points of TH-IR axons and decreased the distance between varicosities. Abnormal patterns of TH-IR axons around intrinsic cardiac ganglia were also found following CIH. We postulate that the increased sympathetic innervation may further amplify the effects of enhanced CIH-induced central sympathetic drive to the heart. Our work provides an anatomical foundation for the understanding of CIH-induced autonomic imbalance. KEY POINTS: Chronic intermittent hypoxia (CIH, a model for sleep apnoea) causes sympathetic overactivity, cardiovascular remodelling and hypertension. We determined the effect of CIH on sympathetic innervation of the mouse atria. In vivo CIH for 8-10weeks resulted in an aberrant axonal pattern around the principal neurons within intrinsic cardiac ganglia and an increase in the density, branching point, tortuosity of catecholaminergic axons and atrial wall thickness. Utilizing mapping tool available from NIH (SPARC) Program, the topographical distribution of the catecholaminergic innervation of the atria were integrated into a novel 3D heart scaffold for precise anatomical distribution and holistic quantitative comparison between normal and CIH mice. This work provides a unique neuroanatomical understanding of the pathophysiology of CIH-induced autonomic remodelling.

Manipulating mitochondrial dynamics in the NTS prevents diet-induced deficits in brown fat morphology and glucose uptake

AimsBrown adipose tissue (BAT) can produce heat by metabolizing glucose and fatty acids. Activation of BAT is controlled by the central nervous system (CNS) through sympathetic innervation. Dysregulation of signalling molecules in selective CNS areas such as the nucleus of tractus solitarius (NTS) are linked with altered BAT activity, obesity and diabetes. High-fat diet (HFD)-feeding increases mitochondrial fragmentation in the NTS, triggering insulin resistance, hyperphagia and weight gain. Here we sought to determine whether changes in mitochondrial dynamics in the NTS can affect BAT glucose uptake. Main methodsRats received DVC stereotactic surgery for local brain administration of viruses that express mutated Drp1 genes. BAT glucose uptake was measured with PET/CT scans. Biochemical assays and immunohistochemistry determined altered levels of key signalling molecules and neural innervation of BAT. Key findingsWe show that short-term HFD-feeding decreases BAT glucose uptake. However, inhibiting mitochondrial fragmentation in NTS-astrocytes of HFD-fed rats partially restores BAT glucose uptake accompanied by lower blood glucose and insulin levels. Tyrosine Hydroxylase (TH) revealed that rats with inhibited mitochondrial fragmentation in NTS astrocytes had higher levels of catecholaminergic innervation in BAT compared to HFD-fed rats, and did not exhibit HFD-dependent infiltration of enlarged white fat droplets in the BAT. In regular chow-fed rats, increasing mitochondrial fragmentation in the NTS-astrocytes reduced BAT glucose uptake, TH immune-positive boutons and β3-adrenergic receptor levels. SignificanceOur data suggest that targeting mitochondrial dynamics in the NTS-astrocytes could be a beneficial strategy to increase glucose utilization and protect from developing obesity and diabetes.

Catecholaminergic innervation and D2-like dopamine receptor-mediated modulation of brainstem nucleus incertus neurons in the rat

Nucleus incertus (NI) is a brainstem structure involved in the control of arousal, stress responses and locomotor activity. It was reported recently that NI neurons express the dopamine type 2 (D2) receptor that belongs to the D2-like receptor (D2R) family, and that D2R activation in the NI decreased locomotor activity. In this study, using multiplex in situ hybridization, we observed that GABAergic and glutamatergic NI neurons express D2 receptor mRNA, and that D2 receptor mRNA-positive neurons belong to partially overlapping relaxin-3- and cholecystokinin-positive NI neuronal populations. Our immunohistochemical and viral-based retrograde tract-tracing studies revealed a dense innervation of the NI area by fibers containing the catecholaminergic biosynthesis enzymes, tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DBH), and indicated the major sources of the catecholaminergic innervation of the NI as the Darkschewitsch, raphe and hypothalamic A13 nuclei. Furthermore, using whole-cell patch clamp recordings, we demonstrated that D2R activation by quinpirole produced excitatory and inhibitory influences on neuronal activity in the NI, and that both effects were postsynaptic in nature. Moreover, the observed effects were cell-type specific, as type I NI neurons were either excited or inhibited, whereas type II NI neurons were mainly excited by D2R activation. Our results reveal that rat NI receives a strong catecholaminergic innervation and suggest that catecholamines acting within the NI are involved in the control of diverse processes, including locomotor activity, social interaction and nociceptive signaling. Our data also strengthen the hypothesis that the NI acts as a hub integrating arousal-related neuronal information.

Juvenile stress exerts sex-independent effects on anxiety, antidepressant-like behaviours and dopaminergic innervation of the prelimbic cortex in adulthood and does not alter hippocampal neurogenesis

Stress, particularly during childhood, is a major risk factor for the development of depression. Depression is twice as prevalent in women compared to men, which suggests that biological sex also contributes to depression susceptibility. However, the neurobiology underpinning sex differences in the long-term consequences of childhood stress remains unknown. Thus, the aim of this study was to determine whether stress applied during the prepubertal juvenile period (postnatal day 27–29) in rats induces sex-specific changes in anxiety-like behaviour, anhedonia, and antidepressant-like behaviour in adulthood in males and females. The impact of juvenile stress on two systems in the brain associated with these behaviours and that develop during the juvenile period, the mesocorticolimbic dopaminergic system and hippocampal neurogenesis, were also investigated. Juvenile stress altered escape-oriented behaviours in the forced swim test in both sexes, decreased latency to drink a palatable substance in a novel environment in the novelty-induced hypophagia test in both sexes, and decreased open field supported rearing behavior in females. These behavioural changes were accompanied by stress-induced increases in tyrosine hydroxylase immunoreactivity in the prefrontal cortex of both sexes, but not other regions of the mesocorticolimbic dopaminergic system. Juvenile stress did not impact anhedonia in adulthood as measured by the saccharin preference test and had no effect hippocampal neurogenesis across the longitudinal axis of the hippocampus. These results suggest that juvenile stress has long-lasting impacts on antidepressant-like and reward-seeking behaviour in adulthood and these changes may be due to alterations to catecholaminergic innervation of the medial prefrontal cortex.

Cortical Serotonergic and Catecholaminergic Denervation in MPTP-Treated Parkinsonian Monkeys.

Decreased cortical serotonergic and catecholaminergic innervation of the frontal cortex has been reported at early stages of Parkinson's disease (PD). However, the limited availability of animal models that exhibit these pathological features has hampered our understanding of the functional significance of these changes during the course of the disease. In the present study, we assessed longitudinal changes in cortical serotonin and catecholamine innervation in motor-symptomatic and asymptomatic monkeys chronically treated with low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Densitometry and unbiased stereological techniques were used to quantify changes in serotonin and tyrosine hydroxylase (TH) immunoreactivity in frontal cortices of 3 control monkeys and 3 groups of MPTP-treated monkeys (motor-asymptomatic [N = 2], mild parkinsonian [N = 3], and moderate parkinsonian [N = 3]). Our findings revealed a significant decrease (P<0.001) in serotonin innervation of motor (Areas 4 and 6), dorsolateral prefrontal (Areas 9 and 46), and limbic (Areas 24 and 25) cortical areas in motor-asymptomatic MPTP-treated monkeys. Both groups of symptomatic MPTP-treated animals displayed further serotonin denervation in these cortical regions (P<0.0001). A significant loss of serotonin-positive dorsal raphe neurons was found in the moderate parkinsonian group. On the other hand, the intensity of cortical TH immunostaining was not significantly affected in motor asymptomatic MPTP-treated monkeys, but underwent a significant reduction in the moderate symptomatic group (P<0.05). Our results indicate that chronic intoxication with MPTP induces early pathology in the corticopetal serotonergic system, which may contribute to early non-motor symptoms in PD.

Testosterone Treatment Mimics Seasonal Downregulation of Dopamine Innervation in the Auditory System of Female Midshipman Fish

In seasonally breeding vertebrates, hormones coordinate changes in nervous system structure and function to facilitate reproductive readiness and success. Steroid hormones often exert their effects indirectly via regulation of neuromodulators, which in turn can coordinate the modulation of sensory input with appropriate motor output. Female plainfin midshipman fish (Porichthys notatus) undergo increased peripheral auditory sensitivity in time for the summer breeding season, improving their ability to detect mates, which is regulated by steroid hormones. Reproductive females also show differences in catecholaminergic innervation of auditory circuitry compared with winter, non-reproductive females as measured by tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholaminergic synthesis. Importantly, catecholaminergic input to the inner ear from a dopaminergic-specific forebrain nucleus is decreased in the summer and dopamine inhibits the sensitivity of the inner ear, suggesting that gonadal steroids may alter auditory sensitivity by regulating dopamine innervation. In this study, we gonadectomized non-reproductive females, implanted them with estradiol (E2) or testosterone (T), and measured TH immunoreactive (TH-ir) fibers in auditory nuclei where catecholaminergic innervation was previously shown to be seasonally plastic. We found that treatment with T, but not E2, reduced TH-ir innervation in the auditory hindbrain. T-treatment also reduced TH-ir fibers in the forebrain dopaminergic cell group that projects to the inner ear, and likely to the auditory hindbrain. Higher T plasma in the treatment group was correlated with reduced-ir TH terminals in the inner ear. These T-treatment induced changes in TH-ir fibers mimic the seasonal downregulation of dopamine in the midshipman inner ear and provide evidence that steroid hormone regulation of peripheral auditory sensitivity is mediated, in part, by dopamine.

Impact of Depletion of Microglia/Macrophages on Regeneration after Spinal Cord Injury

Microglia/macrophages play important functional roles in regeneration after central nervous system injury. Infiltration of circulating macrophages and proliferation of resident microglia occur within minutes following spinal cord injury. Activated microglia/macrophages clear tissue debris, but activation over time may hamper repair. To study the role of these cells in regeneration after spinal cord injury we used CD11b-herpes simplex virus thymidine kinase (HSVTK) (TK) transgenic mice, in which viral thymidine kinase activates ganciclovir toxicity in CD11b-expressing myeloid cells, including macrophages and microglia. A severe reduction in number of these cells was seen in TK versus wild-type littermate mice at 1 week and 5 weeks after injury, and numbers of Mac-2 expressing activated microglia/macrophages were almost completely reduced at these time points. One week after injury TK mice showed better locomotor recovery, but recovery was similar to wild-type mice as measured weekly up to 5 weeks thereafter. At 5 weeks after injury, numbers of axons at the lesion site and neurons in the lumbar spinal cord did not differ between groups. Also, catecholaminergic innervation of spinal motoneurons was similar. However, cholinergic innervation was lower and glial scarring was increased in TK mice compared to wild-type mice. We conclude that reducing numbers of CD11b-expressing cells improves locomotor recovery in the early phase after spinal cord injury, but does not affect recovery in the following 4 weeks. These observations point to differences in outcomes of astrocytic response and cholinergic innervation under CD11b cell ablation, which are, however, not reflected in the locomotor parameters analyzed at 5 weeks after injury.

Catecholaminergic Innervation of the Lateral Nucleus of the Cerebellum Modulates Cognitive Behaviors.

The cerebellum processes neural signals related to rewarding and aversive stimuli, suggesting that the cerebellum supports nonmotor functions in cognitive and emotional domains. Catecholamines are a class of neuromodulatory neurotransmitters well known for encoding such salient stimuli. Catecholaminergic modulation of classical cerebellar functions have been demonstrated. However, a role for cerebellar catecholamines in modulating cerebellar nonmotor functions is unknown. Using biochemical methods in male mice, we comprehensively mapped TH+ fibers throughout the entire cerebellum and known precerebellar nuclei. Using electrochemical (fast scan cyclic voltammetry), and viral/genetic methods to selectively delete Th in fibers innervating the lateral cerebellar nucleus (LCN), we interrogated sources and functional roles of catecholamines innervating the LCN, which is known for its role in supporting cognition. The LCN has the most TH+ fibers in cerebellum, as well as the most change in rostrocaudal expression among the cerebellar nuclei. Norepinephrine is the major catecholamine measured in LCN. Distinct catecholaminergic projections to LCN arise only from locus coeruleus, and a subset of Purkinje cells that are positive for staining of TH. LC stimulation was sufficient to produce catecholamine release in LCN. Deletion of Th in fibers innervating LCN (LCN-Th-cKO) resulted in impaired sensorimotor integration, associative fear learning, response inhibition, and working memory in LCN-Th-cKO mice. Strikingly, selective inhibition of excitatory LCN output neurons with inhibitory designer receptor exclusively activated by designer drugs led to facilitation of learning on the same working memory task impaired in LCN-Th-cKO mice. Collectively, these data demonstrate a role for LCN catecholamines in cognitive behaviors.SIGNIFICANCE STATEMENT Here, we report on interrogating sources and functional roles of catecholamines innervating the lateral nucleus of the cerebellum (LCN). We map and quantify expression of TH, the rate-limiting enzyme in catecholamine synthesis, in the entire cerebellar system, including several precerebellar nuclei. We used cyclic voltammetry and pharmacology to demonstrate sufficiency of LC stimulation to produce catecholamine release in LCN. We used advanced viral techniques to map and selectively KO catecholaminergic neurotransmission to the LCN, and characterized significant cognitive deficits related to this manipulation. Finally, we show that inhibition of excitatory LCN neurons with designer receptor exclusively activated by designer drugs, designed to mimic Gi-coupled catecholamine GPCR signaling, results in facilitation of a working memory task impaired in LCN-specific TH KO mice.

Proarrhythmic atrial ectopy associated with heart sympathetic innervation dysfunctions is specific for murine B6CBAF1 hybrid strain

A lot of animal models are developed with aim to advance in atrial fibrillation (AF) understanding. The hybrid B6CBAF1 mice are used extensively as a background to create manifestation of various diseases, however, their atrial electrophysiology, autonomic sympathetic innervation of the heart and potential for AF investigation is poorly characterized.In the present study we used ECG and microelectrode recordings from multicellular atrial preparations to reveal attributes of atrial electrical activity in B6CBAF1. Also, experiments with a fluorescent false monoamine neurotransmitter and glyoxylic acid-based staining were carried out to characterize functionally and morphologically catecholaminergic innervation of the B6CBAF1 atria.Atrial myocardium of B6CBAF1 is highly prone to ectopic automaticity and exhibits abnormal spontaneous action potential accompanied by multiple postdepolarizations that result in proarrhythmic triggered activity unlike two parental C57Bl/6 and CBA strains. In vivo experiments revealed that B6CBAF1 hybrids are more susceptible to the norepinephrine induced AF. Also, sympathetic nerve terminals are partially dysfunctional in B6CBAF1 revealing lower ability to accumulate and release neurotransmitters unlike two parental strains. The analysis of the heart rate variability revealed suppressed sympathetic component of the autonomic heart control in B6CBAF1. The organization of sympathetic innervation is very similar morphologically in all three murine strains however the abundance of non-bifurcated catecholamine-positive fibers in B6CBAF1 was increased.These results suggest that B6CBAF1 mice exhibit enhanced intrinsic atrial proarrhythmicity, while the abnormalities of sympathetic neurotransmitter cycling probably underlie disturbed autonomic heart control.

Tyrosine hydroxylase containing neurons in the thalamic reticular nucleus of male equids

Here we report the unusual presence of thalamic reticular neurons immunoreactive for tyrosine hydroxylase in equids. The diencephalons of one adult male of four equid species, domestic donkey (Equus africanus asinus), domestic horse (Equus caballus), Cape mountain zebra (Equus zebra zebra) and plains zebra (Equus quagga), were sectioned in a coronal plane with series of sections stained for Nissl substance, myelin, or immunostained for tyrosine hydroxylase, and the calcium-binding proteins parvalbumin, calbindin and calretinin. In all equid species studied the thalamic reticular nucleus was observed as a sheet of neurons surrounding the rostral, lateral and ventral portions of the nuclear mass of the dorsal thalamus. In addition, these thalamic reticular neurons were immunopositive for parvalbumin, but immunonegative for calbindin and calretinin. Moreover, the thalamic reticular neurons in the equids studied were also immunopositive for tyrosine hydroxylase. Throughout the grey matter of the dorsal thalamus a terminal network also immunoreactive for tyrosine hydroxylase was present. Thus, the equid thalamic reticular neurons appear to provide a direct and novel potentially catecholaminergic innervation of the thalamic relay neurons. This finding is discussed in relation to the function of the thalamic reticular nucleus and the possible effect of a potentially novel catecholaminergic pathway on the neural activity of the thalamocortical loop.

Catecholaminergic Innervation of Periventricular Neurogenic Regions of the Developing Mouse Brain.

The major catecholamines—dopamine (DA) and norepinephrine (NE)—are not only involved in synaptic communication but also act as important trophic factors and might ultimately be involved in mammalian brain development. The catecholaminergic innervation of neurogenic regions of the developing brain and its putative relationship to neurogenesis is thus of pivotal interest. We here determined DA and NE innervation around the ventricular/subventricular zone (VZ/SVZ) bordering the whole ventricular system of the developing mouse brain from embryonic day 14.5 (E14.5), E16.5, and E19.5 until postnatal day zero (P0) by histological evaluation and HPLC with electrochemical detection. We correlated these data with the proliferation capacity of the respective regions by quantification of MCM2+ cells. During development, VZ/SVZ catecholamine levels dramatically increased between E16.5 and P0 with DA levels increasing in forebrain VZ/SVZ bordering the lateral ventricles and NE levels raising in midbrain/hindbrain VZ/SVZ bordering the third ventricle, the aqueduct, and the fourth ventricle. Conversely, proliferating MCM2+ cell counts dropped between E16.5 and E19.5 with a special focus on all VZ/SVZs outside the lateral ventricles. We detected an inverse strong negative correlation of the proliferation capacity in the periventricular neurogenic regions (log-transformed MCM2+ cell counts) with their NE levels (r = −0.932; p < 0.001), but not their DA levels (r = 0.440; p = 0.051) suggesting putative inhibitory effects of NE on cell proliferation within the periventricular regions during mouse brain development. Our data provide the first framework for further demandable studies on the functional importance of catecholamines, particularly NE, in regulating neural stem/progenitor cell proliferation and differentiation during mammalian brain development.

Glutamic acid decarboxylase 67 haplodeficiency in mice: consequences of postweaning social isolation on behavior and changes in brain neurochemical systems

Reductions of glutamate acid decarboxylase (GAD67) and subsequent GABA levels have been consistently observed in neuropsychiatric disorders like schizophrenia and depression, but it has remained unclear how GABAergic dysfunction contributes to different symptoms of the diseases. To address this issue, we investigated male mice haplodeficient for GAD67 (GAD67+/GFP mice), which showed a reduced social interaction, social dominance and increased immobility in the forced swim test. No differences were found in rotarod performance and sensorimotor gating. We also addressed potential effects of social deprivation, which is known, during early life, to affect GABAergic function and induces behavioral abnormalities similar to the symptoms found in psychiatric disorders. Indeed, social isolation of GAD67+/GFP mice provoked increased rearing activity in the social interaction test and hyperlocomotion on elevated plus maze. Since GABA closely interacts with the dopaminergic, serotonergic and cholinergic neurotransmitter systems, we investigated GAD67+/GFP and GAD67+/+ mice for morphological markers of the latter systems and found increased tyrosine hydroxylase (TH)-IR fiber densities in CA1 of dorsal hippocampus. By contrast, no differences in numbers and densities of TH-positive neurons of the midbrain dopamine regions, serotonin (5-HT) neurons of the raphe nuclei, or choline acetyltransferase (ChAT)-expressing neurons of basal forebrain and their respective terminal fields were observed. Our results indicate that GAD67 haplodeficiency impairs sociability and increases vulnerability to social stress, provokes depressive-like behavior and alters the catecholaminergic innervation in brain areas associated with schizophrenia. GAD67+/GFP mice may provide a useful model for studying the impact of GABAergic dysfunction as related to neuropsychiatric disorders.

T38. Genetic Dissection of Catecholaminergic Innervation of the Cognitive Cerebellum

Studies in humans and non-human primates have identified a region of the dentate nucleus of the cerebellum (DCN), or lateral nucleus in rodents (LCN), which is activated during performance of cognitive tasks. The DCN is implicated in cognitive function in humans with psychiatric illnesses, but virtually nothing is known about its organization. We hypothesized that the locus coeruleus (LC) is the source of catecholamine release in LCN, catecholamines are required for cerebellar enhancement of cognition, and act on LCN glutamatergic output neurons.

Ventromedial prefrontal cortex is involved in preference and hedonic evaluation of tastes

The ventromedial prefrontal cortex (vmPFC) of rats has reciprocal connections with the gustatory and the hedonic impact coding structures. The main goal of the present study was to investigate the involvement of local neurons of vmPFC and their catecholaminergic innervations in taste preference and taste reactivity test. Therefore, kainate or 6-hydroxydopamine (6-OHDA) lesions were performed in the vmPFC by iontophoretic method. In the first experiment, taste preference was tested to 250 mM and 500 mM glucose solutions over water in two-bottle choice test. In the second experiment, taste reactivity was examined to 4 concentrations of glucose solutions (250 mM, 500 mM, 750 mM and 1000 mM) and 4 concentrations of quinine solutions (0.125 mM, 0.25 mM, 1.25 mM and 2.5 mM). Our results showed, that kainate microlesion of vmPFC did not modify the preference of 250 mM and 500 mM glucose solutions in two-bottle choice test. In contrast, 6-OHDA microlesion of vmPFC resulted in increased preference to the higher concentration of glucose (500 mM) solution over water. Results of taste reactivity test showed that kainate lesion resulted in more ingestive and less rejective responses to 750 mM glucose solution and elevated rejectivity to the higher concentrations (1.25 mM and 2.5 mM) of quinine solutions. 6-OHDA lesion of vmPFC increased the number of ingestive responses to highly concentrated (500 mM, 750 mM and 1000 mM) glucose solutions and decreased the number of ingestive responses to the lower concentration (0.125 mM) of quinine solution. The present data provide evidence for the important role of vmPFC neurons and catecholaminergic innervation of the vmPFC in the regulation of hedonic evaluation of tastes and in the hedonic consummatory behavior.

Iontophoretic microlesions with kainate or 6-hydroxidopamine in ventromedial prefrontal cortex result in deficit in conditioned taste avoidance to palatable tastants

Effects of kainate or 6-hydroxidopamine (6-OHDA) lesions in the ventromedial prefrontal cortex (vmPFC) on taste-related learning and memory processes were examined. Neurotoxins were applied by iontophoretic method to minimize the extent of lesion and the side effects. Acquisition and retention of conditioned taste avoidance (CTA) was tested to different taste stimuli (0.05 M NaCl, 0.01 M saccharin, 0.01 M citrate and 0.00025 M quinine). In the first experiment, palatability index of taste solutions with these concentrations has been determined as strongly palatable (NaCl, saccharin), weakly palatable (citrate) and weakly unpalatable (quinine) taste stimuli. In two other experiments vmPFC lesions were performed before CTA (acquisition) or after CTA (retrieval). Our results showed that both kainate and 6-OHDA microlesions of vmPFC resulted in deficit of CTA acquisition (to NaCl, saccharin and citrate) and retrieval (to NaCl and saccharin). Deficits were specific to palatable tastants, particularly those that are strongly palatable, and did not occur for unpalatable stimulus. The present data provide evidence for the important role of vmPFC neurons and catecholaminergic innervation of the vmPFC in taste related learning and memory processes.

In vivo imaging of inflammation and oxidative stress in a nonhuman primate model of cardiac sympathetic neurodegeneration

Loss of cardiac postganglionic sympathetic innervation is a characteristic pathology of Parkinson’s disease (PD). It progresses over time independently of motor symptoms and is not responsive to typical anti-parkinsonian therapies. Cardiac sympathetic neurodegeneration can be mimicked in animals using systemic dosing of the neurotoxin 6-hydroxydopamine (6-OHDA). As in PD, 6-OHDA-induced neuronal loss is associated with increased inflammation and oxidative stress. To assess the feasibility of detecting changes over time in cardiac catecholaminergic innervation, inflammation, and oxidative stress, myocardial positron emission tomography with the radioligands [11C]meta-hydroxyephedrine (MHED), [11C]PBR28 (PBR28), and [61Cu]diacetyl-bis(N(4))-methylthiosemicarbazone (ATSM) was performed in 6-OHDA-intoxicated adult, male rhesus macaques (n = 10; 50 mg/kg i.v.). The peroxisome proliferator-activated receptor gamma (PPARγ) agonist pioglitazone, which is known to have anti-inflammatory and anti-oxidative stress properties, was administered to five animals (5 mg/kg, PO); the other five were placebo-treated. One week after 6-OHDA, cardiac MHED uptake was significantly reduced in both groups (placebo, 86% decrease; pioglitazone, 82%); PBR28 and ATSM uptake increased in both groups but were attenuated in pioglitazone-treated animals (PBR28 Treatment × Level ANOVA p < 0.002; ATSM Mann–Whitney p = 0.032). At 12 weeks, partial recovery of MHED uptake was significantly greater in the pioglitazone-treated group, dependent on left ventricle circumferential region and axial level (Treatment × Region × Level ANOVA p = 0.034); 12-week MHED uptake significantly correlated with tyrosine hydroxylase immunoreactivity across cardiac anatomy (p < 0.000002). PBR28 and ATSM uptake returned to baseline levels by 12 weeks. These radioligands thus hold potential as in vivo biomarkers of mechanisms of cardiac neurodegeneration and neuroprotection.

Perturbed Developmental Serotonin Signaling Affects Prefrontal Catecholaminergic Innervation and Cortical Integrity

Proper development of the medial prefrontal cortex (mPFC), crucial for correct cognitive functioning, requires projections from, among others, the serotonergic (5-HT) and catecholaminergic systems, but it is unclear how these systems influence each other during development. Here, we describe the parallel development of the 5-HT and catecholaminergic prefrontal projection systems in rat and demonstrate a close engagement of both systems in the proximity of Cajal-Retzius cells. We further show that in the absence of the 5-HT transporter (5-HTT), not only the developing 5-HT but also the catecholaminergic system, including their projections towards the mPFC, are affected. In addition, the layer identity of the mPFC neurons and reelin-positive interneuron number and integration are altered in the absence of the 5-HTT. Together, our data demonstrate a functional interplay between the developing mPFC 5-HT and catecholaminergic systems, and call for a holistic approach in studying neurotransmitter systems-specific developmental consequences for adult behavior, to eventually allow the design of better treatment strategies for neuropsychiatric disorders.

Post-Mortem and In Vivo Assessment of Catecholaminergic Innervation and Alpha-Synuclein Deposition by Multi-Protein Immunofluorescence Microscopy (P1.184)

Post-Mortem and In Vivo Assessment of Catecholaminergic Innervation and Alpha-Synuclein Deposition by Multi-Protein Immunofluorescence Microscopy (P1.184)

EGR-1 Expression in Catecholamine-synthesizing Neurons Reflects Auditory Learning and Correlates with Responses in Auditory Processing Areas

Distinguishing between familiar and unfamiliar individuals is an important task that shapes the expression of social behavior. As such, identifying the neural populations involved in processing and learning the sensory attributes of individuals is important for understanding mechanisms of behavior. Catecholamine-synthesizing neurons have been implicated in sensory processing, but relatively little is known about their contribution to auditory learning and processing across various vertebrate taxa. Here we investigated the extent to which immediate early gene expression in catecholaminergic circuitry reflects information about the familiarity of social signals and predicts immediate early gene expression in sensory processing areas in songbirds. We found that male zebra finches readily learned to differentiate between familiar and unfamiliar acoustic signals (‘songs’) and that playback of familiar songs led to fewer catecholaminergic neurons in the locus coeruleus (but not in the ventral tegmental area, substantia nigra, or periaqueductal gray) expressing the immediate early gene, EGR-1, than playback of unfamiliar songs. The pattern of EGR-1 expression in the locus coeruleus was similar to that observed in two auditory processing areas implicated in auditory learning and memory, namely the caudomedial nidopallium (NCM) and the caudal medial mesopallium (CMM), suggesting a contribution of catecholamines to sensory processing. Consistent with this, the pattern of catecholaminergic innervation onto auditory neurons co-varied with the degree to which song playback affected the relative intensity of EGR-1 expression. Together, our data support the contention that catecholamines like norepinephrine contribute to social recognition and the processing of social information.

The catecholaminergic innervation of the claustrum of the pig.

Over the past decades, the number of studies employing the pig brain as a model for neurochemical studies has dramatically increased. The key translational features of the pig brain are the similarities with the cortical and subcortical structures of the human brain. In addition, the caudalmost part of the pig claustrum (CL) is characterized by a wide enlargement called posterior puddle, an ideal structure for physiological recordings. Several hypotheses have been proposed for CL function, the key factor being its reciprocal connectivity with most areas of the cerebral cortex and selected subcortical structures. However, afferents from the brainstem could also be involved. The brainstem is the main source of catecholaminergic axons that play an important neuromodulatory action in different brain functions. To study a possible role of the CL in catecholaminergic pathways, we analyzed the presence and the distribution of afferents immunostained with antibodies against tyrosine hydroxylase (TH) and dopamine betahydroxylase (DBH) in the pig CL. Here we show that the CL contains significant TH immunoreactive axons contacting perikarya, whereas projections staining for DBH are very scarce. Our findings hint at the possibility that brainstem catecholaminergic afferents project to the CL, suggesting (i) a possible role of this nucleus in functions controlled by brainstem structures; and, consequently, (ii) its potential involvement in the pathophysiology of neurodegenerative pathologies, including Parkinson's disease (PD).