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Chemogenetic activation of noradrenergic A5 neurons increases blood pressure and visceral sympathetic activity in adult rats

Souza, George M P R; Stornetta, Daniel S; Vitali, Alexander J; Wildner, Hendrik; Zeilhofer, Hanns Ulrich; Campbell, John N; Abbott, Stephen B G (2022). Chemogenetic activation of noradrenergic A5 neurons increases blood pressure and visceral sympathetic activity in adult rats. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology, 323(4):R512-R531.

Abstract

In mammals, the pontine noradrenergic system influences nearly every aspect of central nervous system function. A subpopulation of pontine noradrenergic neurons, called A5, are thought to be important in the cardiovascular response to physical stressors, yet their function is poorly defined. We hypothesized that activation of A5 neurons stimulates a sympathetically-mediated increase in BP. To test this hypothesis, we conducted a comprehensive assessment of the cardiovascular effects of chemogenetic stimulation of A5 neurons in male and female adult rats using intersectional genetic and anatomical targeting approaches. Chemogenetic stimulation of A5 neurons in freely behaving rats elevated BP by 15 mmHg and increased cardiac baroreflex sensitivity with a negligible effect on resting HR. Importantly, A5 stimulation had no detectable effect on locomotor activity, metabolic rate or respiration. Under anesthesia, stimulation of A5 neurons produced a marked elevation in visceral sympathetic nerve activity (SNA) and no change in skeletal muscle SNA, showing that A5 neurons preferentially stimulate visceral SNA. Interestingly, projection mapping indicates that A5 neurons target sympathetic preganglionic neurons throughout the spinal cord and parasympathetic preganglionic neurons throughout in the brainstem, as well as the nucleus of the solitary tract, and ventrolateral medulla. Moreover, in situ hybridization and immunohistochemistry indicate that a sub-population of A5 neurons co-release glutamate and monoamines. Collectively, this study suggests A5 neurons are a central modulator of autonomic function with a potentially important role in sympathetically-driven redistribution of blood flow from the visceral circulation to critical organs and skeletal muscle.

Keywords: baroreflex; brainstem; chemogenetics; hypertension; neural circuits

Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Pharmacology and Toxicology
07 Faculty of Science > Institute of Pharmacology and Toxicology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:1 October 2022
Deposited On:27 Sep 2022 14:07
Last Modified:27 Jan 2025 02:41
Publisher:American Physiological Society
ISSN:0363-6119
OA Status:Green
Publisher DOI:https://doi.org/10.1152/ajpregu.00119.2022
PubMed ID:35993562
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