Modulation of cardiorespiratory function mediated by the paraventricular nucleus

Abstract

The hypothalamic paraventricular nucleus (PVN) coordinates autonomic and neuroendocrine systems to maintain homeostasis and to respond to stress. Neuroanatomic and neurophysiologic experiments have provided insight into the mechanisms by which the PVN acts. The PVN projects directly to the spinal cord and brainstem and, specifically, to sites that control cardiorespiratory function: the intermediolateral cell columns and phrenic motor nuclei in the spinal cord and rostral ventrolateral medulla (RVLM) and the rostral nuclei in the ventral respiratory column (rVRC) in the brainstem. Activation of the PVN increases ventilation (both tidal volume and frequency) and blood pressure (both heart rate and sympathetic nerve activity). Excitatory and inhibitory neurotransmitters including glutamate and GABA converge in the PVN to influence its neuronal activity. However, a tonic GABAergic input to the PVN directly modulates excitatory outflow from the PVN. Further, even within the PVN, microinjection of GABA A receptor blockers increases glutamate release suggesting an indirect mechanism by which GABA control contributes to PVN functions. PVN activity alters blood pressure and ventilation during various stresses, such as maternal separation, chronic intermittent hypoxia (CIH), dehydration and hemorrhage. Among the several PVN neurotransmitters and neurohormones, vasopressin and oxytocin modulate ventilation and blood pressure. Here, we review our data indicating that increases in vasopressin and vasopressin type 1A (V 1A ) receptor signaling in the RVLM and rVRC are mechanisms increasing blood pressure and ventilation after exposure to CIH. That blockade of V 1A receptors in the medulla normalizes baseline blood pressure as well as blunts PVN-evoked blood pressure and ventilatory responses in CIH-conditioned animals indicate the role of vasopressin in cardiorespiratory control. In summary, morphological and functional studies have found that the PVN integrates sensory input and projects to the sympathetic and respiratory control systems with descending projections to the medulla and spinal cord. KeywordsRostral ventrolateral medulla; Intermediolateral cell column of the spinal cord; Ventilatory control; Blood pressure; Sympathetic nerve activity

Chronic intermittent hypoxia increases sympathetic control of blood pressure: role of neuronal activity in the hypothalamic paraventricular nucleus

“…However, emerging evidence indicates that persistent neurogenic CIH hypertension involves additional adaptive mechanisms that contribute to heightened sympathetic drive. For example, CIH hypertension involves chronic activation of body fluid and autonomic regulatory regions of the forebrain lamina terminalis (8,27), hypothalamus (7-9, 25, 27, 53), and brain stem (10,26,27,36,70,71). Among lamina terminalis regions activated by CIH, the MnPO appears to be particularly important.…”

Influence of juvenile housing conditions on the ventilatory, thermoregulatory, and endocrine responses to hypoxia of adult male rats

“…In these animals, baseline CORT levels were lower, whereas estradiol and testosterone levels were higher, than those observed in rats housed in pairs, thereby indicating that triad housing reduces the basal level of HPA axis activation. These results and the fact that hypothalamic structures, such as the PVN, modulate both the HPA axis response to stress and respiratory activity (24,25) may explain why housing affected respiratory regulation, whether at rest or during hypoxic challenge.…”

Aerobic Exercise and Eucalyptus Globulus: Cardio-affective effects on recovery and stress

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