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

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.

Suppression of the Swallowing Reflex during Rhythmic Jaw Movements Induced by Repetitive Electrical Stimulation of the Dorsomedial Part of the Central Amygdaloid Nucleus in Rats

“…The onset latency of the first swallow was significantly prolonged during rhythmic jaw movements. A morphological study showed direct GABAergic projection from the CeADM to the NTS [26,27]. It is likely, therefore, that the direct input from the CeADM and the masticatory CPG of the CeADM to the NTS is involved in the extension of the onset latency of the first swallow by stimulation of the CeADM.…”

“…It has been reported that the number of swallows induced by the SLN stimulation was reduced after microinjection of a GABA A agonist into the LRF [33]. The CeADM contains GABAergic inhibitory interneurons [26,27,34]. GABAergic inputs from the CeADM and the masticatory CPG of CeADM may inhibit activation in the ventral region of swallowing CPG.…”

“…No detailed analysis of rhythmic jaw movements induced by stimulation of the CeA has been made, however. Electrophysiological and morphological studies have reported that the CeA projects directly to the NTS [24][25][26][27][28]. Furthermore, the CeA projects to the LRF [28,29].…”

Paraventricular hypothalamic nucleus are essential for arousal promotion and maintenance

“…The PVH has distinct input and output connections that participate in various brain functions. PVH vglut2 neurons are connected to the BF 41 , and PVT 42 , and project to the nucleus of the solitary tract (NTS) 43 , lateral parabrachial nucleus (L-PBN) 16,17 , pre-locus coeruleus (pLC) 31 and ventral lateral septum (LSv) 33 . Our present ndings identi ed two speci c neural circuits, among which the PVH vglut2 →PB/LSv circuit rather than the PVH vglut2 →NTS circuit was required for the maintenance of physiological wakefulness.…”

A survey of the mouse hindbrain in the fed and fasted state using single-nucleus RNA sequencing

“…The area postrema (AP) is a circumventricular organ located within the medulla oblongata below the fourth ventricle, and is, like the hypothalamus, able to detect circulating chemical messengers in the blood and transduce them into neural signals and networks, relaying information to other brain areas [1]. Adjacent to the AP is the nucleus tractus solitaris (NTS) consisting of a collection of subnuclei which receive direct inputs from multiple locations including gustatory information from cranial nerves, and postprandial signals via vagal afferents [2], and thus acts as a visceral sensory relay station within the brain.…”