Neuropeptides and circuits

Our lab investigates how neuropeptides shape synaptic circuits on molecular, electrophysiological and behavioral level.

Neuropeptides are highly diverse signaling molecules that serve as  messengers between neurons and other cell types in the brain to fine tune neuronal networks and behavioral functions. More than 100 different neuropeptides are known so far, however only a minority of these has been thoroughly investigated. 

Our lab seeks to discover new functions of neuropeptides in the regulation of cognition and emotion and reveal underlying mechanisms.  We investigate how neuropeptides modulate ion channels, second messengers, gene transcription and synaptic release machinery components and eventually link this to effects at the level of neuronal circuits and behavior. We use a combination of standard electrophysiological whole-cell patch-clamp recordings and cutting-edge imaging tools to reveal these mechanisms in vitro. For in vivo research, specific tools to manipulate and visualize neuropeptide signaling are still largely missing. Therefore, where needed, we develop new tools for precise manipulation and visualization of peptides, receptors and downstream signaling pathways. These allow us to precisely enhance or downregulate neuropeptidergic signaling in defined neuronal circuits and in various behavioral contexts.

Techniques

The Melzer Lab uses a broad range of techniques to understand the function and mechanisms of neuronal circuits and  neuropeptides, including fiber photometric imaging in freely moving mice, in vitro patch-clamp recordings, CRISPR/Cas9-mediated genetic manipulations, development and imaging of new molecular sensors, optogenetic and chemogenetic investigation of neuronal cell types and various behavioral tasks to test emotional and cognitive functions of brain circuits. 

Photometry: We established photometric in vivo imaging in our lab to study neuronal activity, intracellular pathways and neurotransmitter release in the brain and correlate these to behavioral phenotypes of model organisms.

In vitro imaging: We routinely use in vitro imaging of second messengers including Ca2+ and cAMP to visualize intracellular singaling cascades that are triggered by neuropeptides and other neuromodulators. Moreover, we use in vitro imaging to establish novel tools and validation essays for CRISPR-based genetic manipulation, visualization of peptide release etc.

In vitro patch-clamp recordings: We use whole-cell patch-clamp recordings to identify ion channels, enzymes and second messengers that are involved in peptidergic intracellular signaling. 

Behavioral testing: To test the function of neuromodulators and their downstream signaling pathways, we combine behavioral tests for cognition, anxiety and fear with in vivo manipulation of signaling pathways and neuronal activity. We employ a set of CRISPR-based genetic tools, chemogenetic activation and inhibition tools as well as optogenetics to probe the function of specific proteins, cell types of circuits.

Molecular biology: A range of staining techniques allows us to visualize expression of receptors, peptides and other genes/proteins in selected cell types or neuronal circuits across behavioral states and after specific genetic ablation of signaling pathways. 

Data analysis: All data are processed with automated MATLAB- and PYTHON-based analysis pipelines that are collaboratively developed in our team. Where needed, we incorporate publicly available software such as for high throughput analysis of complex imaging data.

Tool development: Our lab develops circuit-specific techniques to enhance or decrease neuropeptide signaling. Our techniques include CRISPR-based editing, gene overexpression and UV-uncaging for neuropeptide release. Moreover, we develop tools to visualize peptides and downstream signaling pathways, including genetically encoded fluorescent sensors for peptides and intracellular second messenger signaling. Many of these tools are developed in close collaboration with leading international bioengineering labs. If you are interested in any of our new technologies, please get in touch.

Ongoing Projects

#1: ERC-StG (2022-2027): Neuropeptidergic modulation of synaptic circuits in fear and anxiety

In this project, we explores the role of neuropeptides in the regulation of fear, fear memory and anxiety. We investigate which neuropeptides are released in the brain in response to threats, aversive and anxiogenic stimuli and how these neuropeptides modulate the activity and molecular machinery of neurons in relevant neuronal networks. Detailed neuronal mechanisms will be tested for their function in the expression of fearful and anxiogenic behavior.

#2: WWTF VRG (2022-2027): Neuronal and neuropeptidergic mechanisms for flexible control of learning and memory

This project explores how selected neuropeptides modulate learning and memory. We are aiming to understand how neuropeptides modulate neuronal networks that are involved in the formation and retrieval of positive and negative association memories. Relevant behavioral tests are employed in combination with genetic and optical tools to reveal the underlying molecular pathways and visualize network computations that contribute to the processing of relevant sensory and affective information. The project is generously funded by the Vienna Science and Technology Fund (WWTF). More information on the funding source can be found here: www.wwtf.at