The ability of organisms to sense – and properly respond to – their environment is crucial to their survival. Higher organisms communicate with conspecifics to ensure the survival of the species. Nematodes, such as the roundworm Caenorhabditis elegans, are ubiquitous across all biomes, and rely on chemical communication to convey information with one another. The small molecules they utilize in this communication are called ascarosides. These modular pheromones are employed by all taxa, ranging from Caenorhabditis to Ascaris. The ascaroside, ascr#8, is release by hermaphroditic C. elegans to attract potential mates. Previous work has shown that a class of male specific neurons are required for sensation of this pheromone. Here, we show that these neurons initiate a neural circuit modulated by the FMRFamide-like neuropeptide, flp-3. This neuropeptide is sensed by a set of G protein-coupled receptors (GPCRs), NPR-10 and FRPR-16. Together, these components determine the behavioral valence of males to ascr#8. Within the male-specific sensory neurons, the CEM, we show that another group of GPCRs sense the ascr#8. Two of these receptors, DMSR-12 and SRW-97, are expressed in the cilia, suggesting their involvement in direct sensation of the cue. As a targeted approach to identifying and confirming receptors for ascr#8, we have developed a bioactive photoaffinity probe. We have also confirmed that the ability of ascr#8 to attract males is conserved across the genus. Together, these studies coalesce to deepen our understanding of sex-specific chemosensation and neuronal processing. These results can be used to better understand the defects that are seen in neurodegenerative diseases – many of which exhibit sex-specific defects in neuronal processing.

Background Myocardial infarction (MI) induces remodeling in stellate ganglion neurons (SGNs). Objective We investigated whether infarct site has any impact on the laterality of morphologic changes or neuropeptide expression in stellate ganglia. Methods Yorkshire pigs underwent left circumflex coronary artery (LCX; n = 6) or right coronary artery (RCA; n = 6) occlusion to create left- and right-sided MI, respectively (control: n = 10). At 5 ± 1 weeks after MI, left and right stellate ganglia (LSG and RSG, respectively) were collected to determine neuronal size, as well as tyrosine hydroxylase (TH) and neuropeptide Y immunoreactivity. Results Compared with control, LCX and RCA MIs increased mean neuronal size in the LSG (451 ± 25 vs 650 ± 34 vs 577 ± 55 μm2, respectively; P =.0012) and RSG (433 ± 22 vs 646 ± 42 vs 530 ± 41 μm2, respectively; P =.002). TH immunoreactivity was present in the majority of SGNs. Both LCX and RCA MIs were associated with significant decreases in the percentage of TH-negative SGNs, from 2.58% ± 0.2% in controls to 1.26% ± 0.3% and 0.7% ± 0.3% in animals with LCX and RCA MI, respectively, for LSG (P =.001) and from 3.02% ± 0.4% in controls to 1.36% ± 0.3% and 0.68% ± 0.2% in LCX and RCA MI, respectively, for RSG (P =.002). Both TH-negative and TH-positive neurons increased in size after LCX and RCA MI. Neuropeptide Y immunoreactivity was also increased significantly by LCX and RCA MI in both ganglia. Conclusion Left- and right-sided MIs equally induced morphologic and neurochemical changes in LSG and RSG neurons, independent of infarct site. These data indicate that afferent signals transduced after MI result in bilateral changes and provide a rationale for bilateral interventions targeting the sympathetic chain for arrhythmia modulation.

The presence of vasoactive intestinal polypeptide (VIP) has been analyzed in fibers and neurons within the guinea pig intrinsic cardiac ganglia and in fibers innervating cardiac tissues. In whole-mount preparations, VIP-immunoreactive (IR) fibers were present in about 70% of the cardiac ganglia. VIP was co-localized with neuronal nitric oxide synthase (nNOS) in fibers innervating the intrinsic ganglia but was not present in fibers immunoreactive for pituitary adenylate cyclase-activating polypeptide, choline acetyltransferase (ChAT), tyrosine hydroxylase, or substance P. A small number of the intrinsic ChAT-IR cardiac ganglia neurons (approximately 3%) exhibited VIP immunoreactivity. These few VIP-IR cardiac neurons also exhibited nNOS immunoreactivity. After explant culture for 72 h, the intraganglionic VIP-IR fibers degenerated, indicating that they were axons of neurons located outside the heart. In cardiac tissue sections, VIP-IR fibers were present primarily in the atria and in perivascular connective tissue, with the overall abundance being low. VIP-IR fibers were notably sparse in the sinus node and conducting system and generally absent in the ventricular myocardium. Virtually all VIP-IR fibers in tissue sections exhibited immunoreactivity to nNOS. A few VIP-IR fibers, primarily those located within the atrial myocardium, were immunoreactive for both nNOS and ChAT indicating they were derived from intrinsic cardiac neurons. We suggest that, in the guinea pig, the majority of intraganglionic and cardiac tissue VTP-IR fibers originate outside of the heart. These extrinsic VIP-IR fibers are also immunoreactive for nNOS and therefore most likely are a component of the afferent fibers derived from the vagal sensory ganglia.

Neuropeptide signaling play critical roles in maintaining distinct behavioral states and orchestrating transitions between them. However, elucidating the mechanisms underlying neuropeptide modulation of neural circuits in vivo remains a major challenge. The nematode Caenorhabditis elegans serves as an excellent model organism to study neuropeptide signaling mechanisms encoded in relatively simple neural circuits. We have used the C. elegans egg-laying circuit as a model to understand how neuropeptide signaling modifies circuit activity to generate opposing behavioral outcomes. C. elegans egg-laying behavior is composed of alternating cycles of two states – short bursts of egg deposition (active phases) and prolonged periods of quiescence (inactive phases). We have identified two neuropeptides (NLP-7 and FLP-11) that are locally released from a group of neurosecretory cells (uv1) and coordinate the temporal organization of egglaying by prolonging the duration of inactive phases. These neuropeptides regulate activity within the core circuit by inhibiting serotonergic transmission between its individual components (HSN motorneurons and Vm2 vulval muscles). This inhibition is achieved at least in part, by reducing synaptic vesicle abundance in the HSN synaptic regions. To identify potential downstream signaling components that mediate the actions of these neuropeptides, we have performed a forward genetic screen and have identified a strong candidate. In addition, we are trying to identify the receptor(s) of these neuropeptides by using a candidate gene approach. Together, we demonstrate that local neuropeptide signaling maintains the periodicity of distinct behavioral states by regulating serotonergic transmission in the core neural circuit.

Neuropeptide und ihre Rezeptoren regulieren im menschlichen Körper essentielle Funktionen. Fehlfunktionen können zu schwerwiegenden Krankheiten führen, weswegen die Erforschung dieser Peptid-Rezeptor-Systeme von hohem Wert ist. Die Komplexität der Signalisierung erschwert die Forschung in Säugetiermodellen, weswegen auch Modelle von Invertebraten herangezogen werden können, wo viele homologe Neuropeptide zu finden sind. In dieser Arbeit wurde das ein Homolog zum Neuropeptid Y (NPY) im Rundwurm Caenorhabditis elegans (C. elegans) identifiziert und charakterisiert. Das NPY-System besteht aus 3 Peptiden und 4 Rezeptoren, welche in Säugetieren vor allem den Energiehaushalt regulieren, aber auch bei Stress, Depression und Angstzuständen eine Rolle spielen. In C. elegans wurden 41 dem NPY ähnliche Rezeptoren (NPR) und über 30 Neuropeptide identifiziert, welche auch Funktionen in der Nahrungssuche zeigen. In dieser Arbeit wurde gezeigt, dass das humane und C. elegans System pharmakologische und funktionale Gemeinsamkeiten aufweisen. Hier wurden der NPR-1 und NPR-11 als NPY-ähnlichste Rezeptoren identifiziert und erstmals ein NPY-ähnliches Peptid beschrieben, das FLP-34-1. Des Weiteren wurde eine bekannte Methode für Zellkulturexperimente in C. elegans etabliert, der Biolumineszenz-Energietransfer (BRET), welcher die Bindung von FLP-34-1 an NPR-11 in vivo zeigte. Zudem konnte mit dieser Methode eine Peptid-induzierte Internalisierung von NPR-11 Richtung Endosomen in vivo in Echtzeit gezeigt werden. Die Ergebnisse dieser Arbeit helfen die molekularen Mechanismen der Peptid-Rezeptor-Interaktionen besser zu verstehen und unterstützen damit auch die Forschung an höheren Tieren.

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Circadian rhythms in physiology and behavior are synchronized by a central pacemaker, the suprachiasmatic nuclei (SCN) of the hypothalamus. Shift work, jet lag and sleep disorders can disrupt circadian rhythms, negatively impacting health and well-being. The SCN pacemaker resets rapidly in response to changes in the daily light cycle, however, adjustment of peripheral oscillators to changing time zones or work shifts is more gradual, leading to internal desynchrony. In addition, many diseases can impair the SCN’s ability to adjust to changes in the light cycle. My research investigated whether combined pharmacological inhibition of neuropeptide Y and serotonin could enhance resetting and attenuate transient cycles in locomotor activity following a sudden change in light exposure. I found that simultaneously blocking neuropeptide Y and serotonin receptors potentiated phase shifts during the late subjective night and significantly reduced transient cycles of locomotor activity in hamsters. Development of treatments that enhance the circadian system’s response to light may alleviate some of the negative health consequences experienced by travelers, shift workers and individuals with disease-related circadian desynchrony.

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