• fiber photometry
• calcium imaging
• noradrenaline
• anxiety
• drn
• dorsal raphe nucleus
• astrocytes

The Dorsal Raphe Nucleus (DRN) not only is the largest of the serotonergic nuclei, containing approximately a third of all serotonergic neurons (DRN5-HT), but it comprises also a wide variety of neuronal subpopulations, including dopaminergic cells (DRNDA) and astrocytes, which may represent a source of local DRN modulation. The DRN plays a role in a wide range of behavioural responses related to the processing of aversive stimuli, leading to anxiety state. Despite the role of DRN5-HT and DRNDA in anxiety-like and stress responses having been previously investigated, the contribution of DRN astrocytes, as well as the underpinning cellular mechanisms, remain elusive.
Unpublished data from the lab indicates that the presentation of aversive stimuli triggers a reliable increase in noradrenergic (NE) signal in the DRN. Furthermore, in freely moving mice, optogenetic stimulation of LC projections to the DRN decreases the speed and distance travelled, which might indicate freezing responses.
In this study, we aimed to investigate the role of LCNE in regulating DRN astrocytes during Pavlovian learning processes that elicit anxiety-like behaviour. To this purpose, we combined intersectional viral strategies, ex vivo Two-Photon Ca2+ imaging, and in vivo Fiber-Photometry in a behavioural task based on the presentation of compound stimuli following Pavlovian learning. A similar behavioural conceptualization has been shown to reliably assess anxiety in multiple species, including non-human primates and humans. Thus, the results of our investigation could be instrumental to relate dysfunctional DRN modulation and encompassing circuit network to the development of comorbid affective symptoms in neurological disorders characterized by astrocyte involvement, such as neurodegenerative diseases, stroke, epilepsy, migraine, and neuroinflammatory diseases.