The nucleus tractus solitarius (NTS) is the primary brain region for receiving and integrating cardiovascular afferent signals. It plays a crucial role in maintaining balance of autonomic nervous system and regulating blood pressure through cardiovascular reflexes. Neurons within the NTS form complex synaptic connections and interact reciprocally with other brain regions. The NTS regulates autonomic nervous system activity and arterial blood pressure through modulating baroreflex, sympathetic nerve activity, renin-angiotensin-aldosterone system, and oxidative stress. Dysfunctions in NTS activity may contribute to hypertension. Understanding the NTS' role in centrally regulating blood pressure and alterations of neurotransmission or signaling pathways in the NTS may provide rationale for new therapeutic strategies of prevention and treatment. This review summarizes the research findings on autonomic nervous system regulation and arterial blood pressure control by NTS, as well as unresolved questions, in order to provide reference for future investigation.
Solitary Nucleus/physiopathology* ; Hypertension/physiopathology* ; Humans ; Animals ; Autonomic Nervous System/physiopathology* ; Blood Pressure/physiology* ; Baroreflex/physiology* ; Renin-Angiotensin System/physiology* ; Sympathetic Nervous System/physiology*

The central amygdala (CeA) is a crucial modulator of emotional, behavioral, and autonomic functions, including cardiovascular responses. Despite its importance, the specific circuit by which the CeA modulates blood pressure remains insufficiently explored. Our investigations demonstrate that photostimulation of GABAergic neurons in the centromedial amygdala (CeM^GABA), as opposed to those in the centrolateral amygdala (CeL), produces a depressor response in both anesthetized and freely-moving mice. In addition, activation of CeM^GABA axonal terminals projecting to the nucleus tractus solitarius (NTS) significantly reduces blood pressure. These CeM^GABA neurons form synaptic connections with NTS neurons, allowing for the modulation of cardiovascular responses by influencing the caudal or rostral ventrolateral medulla. Furthermore, CeM^GABA neurons targeting the NTS receive dense inputs from the CeL. Consequently, stimulation of CeM^GABA neurons elicits hypotension through the CeM-NTS circuit, offering deeper insights into the cardiovascular responses associated with emotions and behaviors.
Animals ; GABAergic Neurons/physiology* ; Male ; Central Amygdaloid Nucleus/physiopathology* ; Hypotension/physiopathology* ; Mice ; Blood Pressure/physiology* ; Mice, Inbred C57BL ; Solitary Nucleus/physiology* ; Photic Stimulation ; Neural Pathways/physiology*

The nucleus tractus solitarii (NTS) is one of the morphologically and functionally defined centers that engage in the autonomic regulation of cardiovascular activity. Phenotypically-characterized NTS neurons have been implicated in the differential regulation of blood pressure (BP). Here, we investigated whether phenylethanolamine N-methyltransferase (PNMT)-expressing NTS (NTS^PNMT) neurons contribute to the control of BP. We demonstrate that photostimulation of NTS^PNMT neurons has variable effects on BP. A depressor response was produced during optogenetic stimulation of NTS^PNMT neurons projecting to the paraventricular nucleus of the hypothalamus, lateral parabrachial nucleus, and caudal ventrolateral medulla. Conversely, photostimulation of NTS^PNMT neurons projecting to the rostral ventrolateral medulla produced a robust pressor response and bradycardia. In addition, genetic ablation of both NTS^PNMT neurons and those projecting to the rostral ventrolateral medulla impaired the arterial baroreflex. Overall, we revealed the neuronal phenotype- and circuit-specific mechanisms underlying the contribution of NTS^PNMT neurons to the regulation of BP.
Solitary Nucleus/metabolism* ; Blood Pressure/physiology* ; Phenylethanolamine N-Methyltransferase/metabolism* ; Neurons/metabolism* ; Paraventricular Hypothalamic Nucleus/metabolism*

Objective To examine the neuroanatomical substrates underlying the effects of minocycline in alleviating lipopolysaccharide (LPS)-induced neuroinflammation. Methods Forty C57BL/6 male mice were randomly and equally divided into eight groups. Over three conse-cutive days, saline was administered to four groups of mice and minocycline to the other four groups. Immediately after the administration of saline or minocycline on the third day, two groups of mice were additionally injected with saline and the other two groups were injected with LPS. Six or 24 hours after the last injection, mice were sacrificed and the brains were removed. Immunohistochemical staining across the whole brain was performed to detect microglia activation via Iba1 and neuronal activation via c-Fos. Morphology of microglia and the number of c-Fo-positive neurons were analyzed by Image-Pro Premier 3D. One-way ANOVA and Fisher's least-significant differences were employed for statistical analyses. Results Minocycline alleviated LPS-induced neuroinflammation as evidenced by reduced activation of microglia in multiple brain regions, including the shell part of the nucleus accumbens (Acbs), paraventricular nucleus (PVN) of the hypothalamus, central nucleus of the amygdala (CeA), locus coeruleus (LC), and nucleus tractus solitarius (NTS). Minocycline significantly increased the number of c-Fo-positive neurons in NTS and area postrema (AP) after LPS treatment. Furthermore, in NTS-associated brain areas, including LC, lateral parabrachial nucleus (LPB), periaqueductal gray (PAG), dorsal raphe nucleus (DR), amygdala, PVN, and bed nucleus of the stria terminali (BNST), minocycline also significantly increased the number of c-Fo-positive neurons after LPS administration. Conclusion Minocycline alleviates LPS-induced neuroinflammation in multiple brain regions, possibly due to increased activation of neurons in the NTS-associated network.
Animals ; Female ; Lipopolysaccharides/toxicity* ; Male ; Mice ; Mice, Inbred C57BL ; Minocycline/pharmacology* ; Neuroinflammatory Diseases ; Solitary Nucleus

Leptin, an adipocyte-derived peptide hormone, has been shown to facilitate breathing. However, the central sites and circuit mechanisms underlying the respiratory effects of leptin remain incompletely understood. The present study aimed to address whether neurons expressing leptin receptor b (LepRb) in the nucleus tractus solitarii (NTS) contribute to respiratory control. Both chemogenetic and optogenetic stimulation of LepRb-expressing NTS (NTS^LepRb) neurons notably activated breathing. Moreover, stimulation of NTS^LepRb neurons projecting to the lateral parabrachial nucleus (LPBN) not only remarkably increased basal ventilation to a level similar to that of the stimulation of all NTS^LepRb neurons, but also activated LPBN neurons projecting to the preBötzinger complex (preBötC). By contrast, ablation of NTS^LepRb neurons projecting to the LPBN notably eliminated the enhanced respiratory effect induced by NTS^LepRb neuron stimulation. In brainstem slices, bath application of leptin rapidly depolarized the membrane potential, increased the spontaneous firing rate, and accelerated the Ca²⁺ transients in most NTS^LepRb neurons. Therefore, leptin potentiates breathing in the NTS most likely via an NTS-LPBN-preBötC circuit.
Leptin/pharmacology* ; Membrane Potentials ; Neurons/metabolism* ; Solitary Nucleus/metabolism*

Accumulating evidence demonstrates that the nucleus tractus solitarii (NTS) neurons serve as central respiratory chemoreceptors, but the underlying molecular mechanisms remain undefined. The present study investigated the expression of acid-sensitive ether-à-go-go-gene-like (Elk, Kv12) channels in the NTS of mice. Immunofluorescence staining was used to observe the distribution and cellular localization of the Kv12 channels in NTS neurons. Western blot and quantitative real-time PCR (qPCR) were used to evaluate protein and mRNA expression levels of Kv12 channels. The results showed that all of the three members (Kv12.1, Kv12.2, Kv12.3) of the Kv12 channel family were expressed in NTS neurons, and their expressions were co-localized with paired-like homeobox 2b gene (Phox2b) expression. The expression of Kv12.1 mRNA was the largest, whereas the expression of Kv12.3 was the least in the NTS. The results suggest Kv12 channels are expressed in Phox2b-expressing neurons in the NTS of mice, which provides molecular evidence for pH sensitivity in Phox2b-expressing NTS neurons.
Animals ; Mice ; Neurons ; Potassium Channels, Voltage-Gated ; Solitary Nucleus ; Transcription Factors/genetics*

Chronic intermittent hypobaric hypoxia (CIHH) is known to have an anti-hypertensive effect, which might be related to modulation of the baroreflex in rats with renal vascular hypertension (RVH). In this study, RVH was induced by the 2-kidney-1-clip method (2K1C) in adult male Sprague-Dawley rats. The rats were then treated with hypobaric hypoxia simulating 5000 m altitude for 6 h/day for 28 days. The arterial blood pressure (ABP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were measured before and after microinjection of L-arginine into the nucleus tractus solitarii (NTS) in anesthetized rats. Evoked excitatory postsynaptic currents (eEPSCs) and spontaneous EPSCs (sEPSCs) were recorded in anterogradely-labeled NTS neurons receiving baroreceptor afferents. We measured the protein expression of neuronal nitric oxide synthase (nNOS) and endothelial NOS (eNOS) in the NTS. The results showed that the ABP in RVH rats was significantly lower after CIHH treatment. The inhibition of ABP, HR, and RSNA induced by L-arginine was less in RVH rats than in sham rats, and greater in the CIHH-treated RVH rats than the untreated RVH rats. The eEPSC amplitude in NTS neurons receiving baroreceptor afferents was lower in the RVH rats than in the sham rats and recovered after CIHH. The protein expression of nNOS and eNOS in the NTS was lower in the RVH rats than in the sham rats and this decrease was reversed by CIHH. In short, CIHH treatment decreases ABP in RVH rats via up-regulating NOS expression in the NTS.
Animals ; Baroreflex ; physiology ; Blood Pressure ; drug effects ; Hypertension ; metabolism ; Hypoxia ; chemically induced ; Kidney ; drug effects ; metabolism ; Male ; Nitric Oxide Synthase Type I ; drug effects ; metabolism ; Rats, Sprague-Dawley ; Solitary Nucleus ; metabolism

The relationship between the vestibular system and the autonomic nervous system has been well studied in the context of the maintenance of homeostasis to the changing internal and external milieus. The perturbations of the autonomic indexes to the vestibular stimuli have been demonstrated in animal studies. In addition, the fluctuation of the blood pressure and the heart rate with other autonomic symptoms such as nausea, vomiting, and pallor are common manifestations in the wide range of vestibular disorders. At the same time, the disorders of the autonomic nervous system can cause dizziness and vertigo in some group of patients. In the anatomical point of view, the relationship between autonomic and vestibular systems is evident. The afferent signals from each system converge to the nucleus of solitary tract to be integrated in medullary reticular formation and the each pathway from the vestibular and autonomic nervous system is interconnected from medulla to cerebral cortex. In this paper, the reported evidence demonstrating the relationship between autonomic derangement and vestibular disorders is reviewed and the further clinical implications are discussed.
Animals ; Autonomic Nervous System ; Autonomic Nervous System Diseases ; Blood Pressure ; Cerebral Cortex ; Dizziness ; Heart Rate ; Homeostasis ; Humans ; Nausea ; Pallor ; Reticular Formation ; Solitary Nucleus ; Vertigo ; Vomiting

The autonomic nervous system (ANS) integrates the function of the internal organs for the homeostasis against various external environmental changes. The efferent components of the ANS are regulated by sensory signals arising from the viscera as well as non-visceral organs. The central neural networks that integrate these sensory signals and modify visceral motor output are complex, and synaptic reflexes formed in the brainstem and spinal cord integrate behavioral responses and visceral responses through the central neural networks. A detailed understanding of the neural network presented above may explain the role of the vestibular system on the homeostasis more extensively.
Autonomic Nervous System ; Brain Stem ; Homeostasis ; Physiology ; Reflex ; Solitary Nucleus ; Spinal Cord ; Spinal Cord Lateral Horn ; Viscera

Neuronal activities of taste-responsive cells in the nucleus of the solitary tract (NST) are affected by various physiological factors, such as blood glucose level or sodium imbalance. These phenomena suggest that NST taste neurons are under the influence of neural substrates that regulate nutritional homeostasis. In this study, we reviewed a series of in vivo electrophysiological investigations that demonstrate that forebrain nuclei, such as the lateral hypothalamus or central nucleus of the amygdala, send descending projections and modulate neuronal activity of gustatory neurons in the NST. These centrifugal modulations may mediate plasticity of taste response in the NST under different physiological conditions.
Amygdala ; Blood Glucose ; Homeostasis ; Hypothalamus ; Neurons* ; Plastics ; Prosencephalon ; Sodium ; Solitary Nucleus*