Neuroautonomic Regulation and its emotional Modulation in mice

In der vorliegenden Arbeit wurden durch externe Stimuli mit angeborenen oder erlernten aversiven Eigenschaften charakteristische somatomotorische-, neuroautonome- und endokrine Antwortmuster bei Mäusen untersucht. Unkonditionierte Stimuli wie kurzzeitige Berührung, die Erfahrung einer neuen Umgebung (Novelty) oder die Präsentation synthetischen Fuchsgeruchs führten zu einer durch erhöhten Sympathikotonus vermittelten Beschleunigung der Herzfrequenz (Herzrate) in Folge gesteigerter lokomotorischer Aktivität und emotionaler Aktivierung. Aversiv konditionierte auditorische oder kontextuelle Stimuli resultierten in lokomotorischer Inhibition bzw. Freezing, Herzraten- und Blutdruckanstieg und erhöhter Kortikosteronkonzentrationen im Blutplasma. Während die Verhaltensänderungen und die Anpassung der Herzrate schnelle zeitliche Dynamik zeigten, erfolgten Blutdruck und endokrine Antworten verzögert. Herzrate und Blutdruck konnten somit als Indikatoren für konditionierte Furcht mit zeitlich dissoziierenden Antwortmustern charakterisiert werden. Die Retention konditionierter Furcht resultierte in erhöhten Kortikosteronwerten welche die unkonditionierte Kortikosteron-reaktion übertrafen. Daraus wurde geschlussfolgert, dass die auditorische Furchtkonditio-nierung ein Modell für akute emotionale Belastung bzw. Stress repräsentiert.Die pharmakologische Aktivierung des Rezeptorsubtyps 1 des Kortikotropin-freisetzenden Hormons (CRF1) im Zentralnervensystem (ZNS) führte zu erniedrigten basalen Herzraten, abgeschwächter konditionierter Tachykardie und pathologisch erhöhter Herzratenvariabilität. Als zugrunde liegender Mechanismus wird ein erhöhter sympatho-vagaler Antagonismus vorgeschlagen, im Gegensatz zu einem abgeschwächten sympatho-vagalen Antagonismus durch zentrale Aktivierung von Neuropeptid Y-Rezeptoren. Periphere pharmakologische Aktivierung von CRF1 führte zu Herzratenanstieg bei unverändertem Blutdruck, während periphere Aktivierung von CRF2 in Blutdruckabfall und vermutlich Barorezeptorreflex-vermitteltem Herzratenanstieg resultierte. Bei CRF-überproduzierenden Mäusen wurden aufgrund einer fehlenden konditionierten Tachykardie im Ton abhängigen Gedächtnistest, jedoch normalem Herzratenanstieg während des Novelty-Tests kognitive Defizite hypothetisiert. Genetisch modifizierte Mäuse, denen funktionelle CRF1 bzw. CRF2-Rezoptoren fehlten, zeigten normales Verhalten und normale Herzratenantworten auf emotionale Stimuli im Novelty-Test und in der Furchtkonditionierung. Die physiologische Rolle endogenen CRFs bei der Regulation kardiovaskulärer Funktionen bleibt somit unklar. Ein wichtiger Beitrag von CRF zur akuten emotionalen Modulation neuroautonomer Funktion ist unwahrscheinlich, während eine wichtige Rolle endogenen CRFs unter chronischen Stressbedingungen nicht ausgeschlossen werden kann. Auf Basis von Furcht induziertem Verhalten konnte ein Beitrag des dorsalen Hippokampus zur Trace-Furchtkonditionierung festgestellt werden, wenn die zeitliche Trennung (Trace) von konditioniertem (Ton) und unkonditioniertem (US) Stimulus 15-30 s betrug. Aufgrund der trotz Inhibition hippokampaler NMDA-Rezeptoren unbeeinflussten Herzratenantwort wurde auf parallele Gedächtnisfunktionen auditorisch konditionierter Furcht rückgeschlossen

Circuits for State-Dependent Modulation of Locomotion

Brain-wide neural circuits enable bi- and quadrupeds to express adaptive locomotor behaviors in a context- and state-dependent manner, e.g., in response to threats or rewards. These behaviors include dynamic transitions between initiation, maintenance and termination of locomotion. Advances within the last decade have revealed an intricate coordination of these individual locomotion phases by complex interaction of multiple brain circuits. This review provides an overview of the neural basis of state-dependent modulation of locomotion initiation, maintenance and termination, with a focus on insights from circuit-centered studies in rodents. The reviewed evidence indicates that a brain-wide network involving excitatory circuit elements connecting cortex, midbrain and medullary areas appears to be the common substrate for the initiation of locomotion across different higher-order states. Specific network elements within motor cortex and the mesencephalic locomotor region drive the initial postural adjustment and the initiation of locomotion. Microcircuits of the basal ganglia, by implementing action-selection computations, trigger goal-directed locomotion. The initiation of locomotion is regulated by neuromodulatory circuits residing in the basal forebrain, the hypothalamus, and medullary regions such as locus coeruleus. The maintenance of locomotion requires the interaction of an even larger neuronal network involving motor, sensory and associative cortical elements, as well as defined circuits within the superior colliculus, the cerebellum, the periaqueductal gray, the mesencephalic locomotor region and the medullary reticular formation. Finally, locomotor arrest as an important component of defensive emotional states, such as acute anxiety, is mediated via a network of survival circuits involving hypothalamus, amygdala, periaqueductal gray and medullary premotor centers. By moving beyond the organizational principle of functional brain regions, this review promotes a circuit-centered perspective of locomotor regulation by higher-order states, and emphasizes the importance of individual network elements such as cell types and projection pathways. The realization that dysfunction within smaller, identifiable circuit elements can affect the larger network function supports more mechanistic and targeted therapeutic intervention in the treatment of motor network disorders

Anxiety and Startle Phenotypes in Glrb Spastic and Glra1 Spasmodic Mouse Mutants

A GWAS study recently demonstrated single nucleotide polymorphisms (SNPs) in the human GLRB gene of individuals with a prevalence for agoraphobia. GLRB encodes the glycine receptor (GlyRs) β subunit. The identified SNPs are localized within the gene flanking regions (3′ and 5′ UTRs) and intronic regions. It was suggested that these nucleotide polymorphisms modify GlyRs expression and phenotypic behavior in humans contributing to an anxiety phenotype as a mild form of hyperekplexia. Hyperekplexia is a human neuromotor disorder with massive startle phenotypes due to mutations in genes encoding GlyRs subunits. GLRA1 mutations have been more commonly observed than GLRB mutations. If an anxiety phenotype contributes to the hyperekplexia disease pattern has not been investigated yet. Here, we compared two mouse models harboring either a mutation in the murine Glra1 or Glrb gene with regard to anxiety and startle phenotypes. Homozygous spasmodic animals carrying a Glra1 point mutation (alanine 52 to serine) displayed abnormally enhanced startle responses. Moreover, spasmodic mice exhibited significant changes in fear-related behaviors (freezing, rearing and time spent on back) analyzed during the startle paradigm, even in a neutral context. Spastic mice exhibit reduced expression levels of the full-length GlyRs β subunit due to aberrant splicing of the Glrb gene. Heterozygous animals appear normal without an obvious behavioral phenotype and thus might reflect the human situation analyzed in the GWAS study on agoraphobia and startle. In contrast to spasmodic mice, heterozygous spastic animals revealed no startle phenotype in a neutral as well as a conditioning context. Other mechanisms such as a modulatory function of the GlyRs β subunit within glycinergic circuits in neuronal networks important for fear and fear-related behavior may exist. Possibly, in human additional changes in fear and fear-related circuits either due to gene-gene interactions e.g., with GLRA1 genes or epigenetic factors are necessary to create the agoraphobia and in particular the startle phenotype

Deep learning-enabled segmentation of ambiguous bioimages with deepflash2

The signal-to-noise ratio in bioimages is often low, which is problematic for segmentation. Here the authors report a deep learning method, deepflash2, to facilitate the segmentation of ambiguous bioimages through multi-expert annotations and integrated quality assurance

Dissociation of temporal dynamics of heart rate and blood pressure responses elicited by conditioned fear but not acoustic startle

Fear-inducing stimuli were hypothesized to elicit fast heart rate (HR) responses but slow mean arterial blood pressure (MAP) responses and thus were studied in auditory fear conditioning and acoustic startle at high temporal resolution in freely moving mice and rats. Fear-induced instantaneous acceleration of HR reaching maximum physiological values and subsequent recovery to baseline were observed. The MAP response consisted of an immediate, mild, and transient increase followed by a sluggish, profound elevation and slow recovery. HR and MAP responses served as reliable indicators of conditioned fear in mice with dissociated temporal dynamics. Unconditioned auditory stimuli, including acoustic startle stimuli, elicited only fast, mild, and transient MAP and HR elevations in mice and rats, reflecting arousal and attention under these experimental conditions

Activation of central CRF receptor 1 by cortagine results in enhanced passive coping with a naturalistic threat in mice

CRF receptor subtype 1 (CRF1), abundantly expressed in the central nervous system, has been implicated in defensive behavior in rodents. Pharmacological activation of CRF1 by peptidic agonists results in enhancement of anxiety-like behavior. However, receptor specificity of commonly used agonists was confounded by significant affinity to other receptors and widely used laboratory tests of experimental anxiety suffer from artificial aversive stimulation (e.g. electric shock), and limited measures of anxiety-like behavior. We used the recently developed, CRF1-selective agonist cortagine in a mouse model of defensive behaviors under semi-natural conditions, the Rat Exposure Test (RET). Cortagine was injected bilaterally into the cerebral ventricles (i.c.v.) of male C57Bl/6J mice, 20 min before exposure to a rat in specifically designed box that evokes a wide variety of defensive behaviors such as active/passive avoidance, freezing, risk assessment, and burying. Pre-injection of the CRF receptor antagonist acidic astressin was used to test for receptor specificity of the observed cortagine effects. A control experiment with no rat present was performed to test for baseline effects of cortagine in the exposure setup. Cortagine dose-dependently enhanced passive avoidance and freezing while burying was decreased. CRF receptor antagonism reliably blocked the effects of cortagine. Our results confirm previous findings of anxiogenic-like effects of cortagine, and demonstrate the usefulness of the RET in investigating differential pattering of drug-induced anxiety-like behavior in mice. In conclusion, our results suggest that CRF1 activation in forebrain areas promotes passive coping with the natural threat presented in the RET

Compromised trigemino-coerulean coupling in migraine sensitization can be prevented by blocking beta-receptors in the locus coeruleus

Abstract Background Migraine is a disabling neurological disorder, characterized by recurrent headaches. During migraine attacks, individuals often experience sensory symptoms such as cutaneous allodynia which indicates the presence of central sensitization. This sensitization is prevented by oral administration of propranolol, a common first-line medication for migraine prophylaxis, that also normalized the activation of the locus coeruleus (LC), considered as the main origin of descending noradrenergic pain controls. We hypothesized that the basal modulation of trigeminal sensory processing by the locus coeruleus is shifted towards more facilitation in migraineurs and that prophylactic action of propranolol may be attributed to a direct action in LC through beta-adrenergic receptors. Methods We used simultaneous in vivo extracellular recordings from the trigeminocervical complex (TCC) and LC of male Sprague–Dawley rats to characterize the relationship between these two areas following repeated meningeal inflammatory soup infusions. Von Frey Hairs and air-puff were used to test periorbital mechanical allodynia. RNAscope and patch-clamp recordings allowed us to examine the action mechanism of propranolol. Results We found a strong synchronization between TCC and LC spontaneous activities, with a precession of the LC, suggesting the LC drives TCC excitability. Following repeated dural-evoked trigeminal activations, we observed a disruption in coupling of activity within LC and TCC. This suggested an involvement of the two regions’ interactions in the development of sensitization. Furthermore, we showed the co-expression of alpha-2A and beta-2 adrenergic receptors within LC neurons. Finally propranolol microinjections into the LC prevented trigeminal sensitization by desynchronizing and decreasing LC neuronal activity. Conclusions Altogether these results suggest that trigemino-coerulean coupling plays a pivotal role in migraine progression, and that propranolol’s prophylactic effects involve, to some extent, the modulation of LC activity through beta-2 adrenergic receptors. This insight reveals new mechanistic aspects of LC control over sensory processing