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Localization of the Locus Coeruleus in the Mouse Brain
Published on: March 7, 2019
Forebrain GABAergic projections to locus coeruleus in mouse.
Eugene L Dimitrov1, Yuchio Yanagawa, Ted B Usdin
1Section on Fundamental Neuroscience, National Institute of Mental Health, Bethesda, Maryland 20892, USA.
The Journal of Comparative Neurology
|January 9, 2013
Summary
This study identifies GABAergic neurons in the central amygdala and posterior lateral hypothalamus that inhibit the locus coeruleus (LC). These findings reveal key inhibitory pathways controlling noradrenergic activity in the brain.
Area of Science:
- Neuroscience
- Neuroanatomy
- Cellular Neuroscience
Background:
- The noradrenergic locus coeruleus (LC) is crucial for regulating arousal, memory, and pain.
- Forebrain projections to the LC are well-documented in various species but not systematically mapped in mice.
- Understanding these projections is key to deciphering LC's role in diverse brain functions.
Purpose of the Study:
- To systematically map mouse forebrain projections to the LC.
- To identify the specific neuronal populations, particularly GABAergic neurons, involved in these projections.
- To elucidate the inhibitory control mechanisms exerted by forebrain regions onto the LC.
Main Methods:
- Retrograde and anterograde tracing techniques (Fluoro-Gold, biotinylated dextran amine, viral tracers) were employed.
- GABAergic neurons were identified using green fluorescent protein (GFP) expression and GAD65/67 immunoreactivity.
- Advanced viral tracing (herpes virus) and optogenetics (channelrhodopsin-2) were used to confirm direct neuronal targeting and functional connections.
Main Results:
- Major LC inputs originate from the central amygdalar nucleus (CAmy), anterior hypothalamus, paraventricular nucleus, and posterior lateral hypothalamic area (PLH).
- Over one-third of LC-projecting neurons in the CAmy and PLH were identified as GABAergic.
- GABAergic fibers from CAmy and PLH were observed to directly contact noradrenergic neurons within the LC.
Conclusions:
- This study provides a comprehensive description of GABAergic projections from the CAmy and PLH to the LC in mice.
- These findings highlight significant sources of inhibitory control over central nervous system noradrenergic activity.
- The results clarify previously unknown pathways modulating LC function, impacting our understanding of arousal, memory, and pain regulation.
