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Central afferents to the nucleus of the solitary tract in rats and mice
Journal article   Open access   Peer reviewed

Central afferents to the nucleus of the solitary tract in rats and mice

Silvia Gasparini, Jacob M Howland, Andrew J Thatcher and Joel C Geerling
Journal of comparative neurology (1911), Vol.528(16), pp.2708-2728
11/01/2020
DOI: 10.1002/cne.24927
PMCID: PMC7942812
PMID: 32307700
url
https://www.ncbi.nlm.nih.gov/pmc/articles/7942812View
Open Access

Abstract

The nucleus of the solitary tract (NTS) regulates life‐sustaining functions ranging from appetite and digestion to heart rate and breathing. It is also the brain's primary sensory nucleus for visceral sensations relevant to symptoms in medical and psychiatric disorders. To better understand which neurons may exert top‐down control over the NTS, here we provide a brain‐wide map of all neurons that project axons directly to the caudal, viscerosensory NTS, focusing on a medial subregion with aldosterone‐sensitive HSD2 neurons. Injecting an axonal tracer (cholera toxin b) into the NTS produces a similar pattern of retrograde labeling in rats and mice. The paraventricular hypothalamic nucleus (PVH), lateral hypothalamic area, and central nucleus of the amygdala (CeA) contain the densest concentrations of NTS‐projecting neurons. PVH afferents are glutamatergic (express Slc17a6/Vglut2) and are distinct from neuroendocrine PVH neurons. CeA afferents are GABAergic (express Slc32a1/Vgat) and are distributed largely in the medial CeA subdivision. Other retrogradely labeled neurons are located in a variety of brain regions, including the cerebral cortex (insular and infralimbic areas), bed nucleus of the stria terminalis, periaqueductal gray, Barrington's nucleus, Kölliker‐Fuse nucleus, hindbrain reticular formation, and rostral NTS. Similar patterns of retrograde labeling result from tracer injections into different NTS subdivisions, with dual retrograde tracing revealing that many afferent neurons project axon collaterals to both the lateral and medial NTS subdivisions. This information provides a roadmap for studying descending axonal projections that may influence visceromotor systems and visceral “mind–body” symptoms. Rats and mice have similar patterns of retrogradely labeled neurons that project axons to the NTS. Afferent neurons in the hypothalamus are glutamatergic, while those in the amygdala are GABAergic. In the paraventricular hypothalamic nucleus, NTS afferent neurons are distinct from neuroendocrine neurons. Injecting retrograde tracers into the medial and lateral NTS subdivisions produce similar patterns of retrograde labeling.
medial prefrontal cortex infralimbic nucleus tractus solitarii nucleus of the solitary tract nucleus tractus solitarius insular cortex solitary nucleus hypothalamus paraventricular retrograde tracing

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