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Abnormal oxygen homeostasis in the nucleus tractus solitarii of the spontaneously hypertensive rat
Author(s) -
Hosford Patrick S.,
Millar Julian,
Ramage Andrew G.,
Mariephtali
Publication year - 2017
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/ep086023
Subject(s) - brainstem , dorsal motor nucleus , stimulation , medicine , vagus nerve stimulation , reflex , somatosensory system , vagus nerve , hemodynamics , spontaneously hypertensive rat , anesthesia , blood pressure , endocrinology , psychiatry
New FindingsWhat is the central question of this study? Arterial hypertension is associated with impaired neurovascular coupling in the somatosensory cortex. Abnormalities in activity‐dependent oxygen consumption in brainstem regions involved in the control of cardiovascular reflexes have not been explored previously.What is the main finding and its importance? Using fast‐cyclic voltammetry, we found that changes in local tissue P O 2in the nucleus tractus solitarii induced by electrical stimulation of the vagus nerve are significantly impaired in spontaneously hypertensive rats. This is consistent with previous observations showing that brainstem hypoxia plays an important role in the pathogenesis of arterial hypertension.The effects of arterial hypertension on cerebral blood flow remain poorly understood. Haemodynamic responses within the somatosensory cortex have been shown to be impaired in the spontaneously hypertensive rat (SHR) model. However, it is unknown whether arterial hypertension affects oxygen homeostasis in vital brainstem areas that control cardiovascular reflexes. In this study, we assessed vagus nerve stimulation‐induced changes in local tissue P O 2( P t O 2) in the caudal nucleus tractus solitarii (cNTS) of SHRs and normotensive Wistar rats. Measurements of P t O 2were performed using a novel application of fast‐cyclic voltammetry, which allows higher temporal resolution of O 2 changes than traditional optical fluorescence techniques. Electrical stimulation of the central cut end of the vagus nerve (ESVN) caused profound reductions in arterial blood pressure along with biphasic changes in P t O 2in the cNTS, characterized by a rapid decrease in P t O 2(‘initial dip’) followed by a post‐stimulus overshoot above baseline. The initial dip was found to be significantly smaller in SHRs compared with normotensive Wistar rats even after ganglionic blockade. The post‐ESVN overshoot was similar in both groups but was reduced in Wistar rats after ganglionic blockade. In conclusion, neural activity‐dependent changes in tissue oxygen in brainstem cardiovascular autonomic centres are significantly impaired in animals with arterial hypertension.