Association of hypertension with coronary artery disease onset in the Lebanese population

The onset of coronary artery disease (CAD) is influenced by cardiovascular risk factors that often occur in clusters and may build on one another. The objective of this study is to examine the relationship between hypertension and CAD age of onset in the Lebanese population. This retrospective analysis was performed on data extracted from Lebanese patients (n = 3,753). Logistic regression examined the association of hypertension with the age at CAD diagnosis after controlling for other traditional risk factors. The effect of antihypertensive drugs and lifestyle changes on the onset of CAD was also investigated. Results showed that hypertension is associated with late onset CAD (OR=0.656, 95% CI=0.504-0.853, p=0.001). Use of antihypertensive drugs showed a similar association with delayed CAD onset. When comparing age of onset in CAD patients with traditional risk factors such as hypertension, diabetes, hyperlipidemia, obesity, smoking and family history of CAD, the age of onset was significantly higher for patients with hypertension compared to those with any of the other risk factors studied (p < 0.001). In conclusion, hypertension and its treatment are associated with late coronary atherosclerotic manifestations in Lebanese population. This observation is currently under investigation to clarify its genetic and/or environmental mechanisms

CONTRÔLE BARORÉFLEXE DE L'ACTIVITÉ NERVEUSE SYMPATHIQUE CHEZ LE RAT

Date de rédaction: Avril - Septembre 2008In the rat, a spontaneous index of the sensitivity of the baroreflex control of sympathetic nerve activity (SNA) has been developed, validated and applied. It is based on the calculation of the transfer function gain between arterial pressure (AP) and SNA, at heart rate frequency.Cardiac pacing, in anesthetized rats, showed that this gain is not influenced by heart rate fluctuations. By measuring renal SNA in conscious rats with either intact or partially denervated baroreceptors, it was found that this index is positively correlated with the baroreflex sensitivity measured by the pharmacological method. The functional relevance of this index was confirmed by the existence of an inverse relationship with AP variability. In intact rats, acute exposure to air jet stress sensitized the baroreflex control of renal SNA, when assessed with either method.This index, calculated over 1-min consecutive periods in conscious rats revealed that the sensitivity of the baroreflex control of renal SNA fluctuates spontaneously over time. The computation of this index using both renal and lumbar SNAs, simultaneously recorded in conscious rats, pointed to a homogenous baroreflex regulation of regional SNAs.Chez le rat, un index spontané de mesure de la sensibilité du contrôle baroréflexe de l'activité nerveuse sympathique (ANS) a été développé, validé et appliqué. Il est fondé sur le calcul du gain de la fonction de transfert entre la pression artérielle et l'ANS, à la fréquence cardiaque.L'entraînement cardiaque, chez l'animal anesthésié, révèle que ce gain n'est pas influencé par les variations du rythme cardiaque. En mesurant l'ANS rénale chez des rats vigils ayant des barorécepteurs intacts ou partiellement dénervés, il est montré que cet index est positivement corrélé à la sensibilité baroréflexe mesurée par méthode pharmacologique. L'intérêt fonctionnel de cet index est confirmé par l'existence d'une relation inverse avec la variabilité tensionnelle. Chez des rats intacts, l'application aiguë d'un stress émotionnel par jet d'air sensibilise le contrôle baroréflexe de l'ANS rénale, et ceci quelle que soit la méthode d'évaluation utilisée.Cet index, calculé sur des périodes successives d'une minute, chez des rats éveillés, révèle que la sensibilité du contrôle baroréflexe de l'ANS rénale fluctue spontanément au cours du temps. Le calcul de cet index au moyen des ANSs rénale et lombaire, enregistrées simultanément chez des rats vigils, suggère une régulation baroréflexe homogène des ANS régionales

Contrôle baroréflexe de l'activité nerveuse sympathique chez le rat

In the rat, a spontaneous index of the sensitivity of the baroreflex control of sympathetic nerve activity (SNA) has been developed, validated and applied. It is based on the calculation of the transfer function gain between arterial pressure (AP) and SNA, at heart rate frequency. Cardiac pacing, in anesthetized rats, showed that this gain is not influenced by heart rate fluctuations. By measuring renal SNA in conscious rats with either intact or partially denervated baroreceptors, it was found that this index is positively correlated with the baroreflex sensitivity measured by the pharmacological method. The functional relevance of this index was confirmed by the existence of an inverse relationship with AP variability. In intact rats, acute exposure to air jet stress sensitized the baroreflex control of renal SNA, when . This index, calculated over 1-min consecutive periods in conscious rats revealed that the sensitivity of the baroreflex control of renal SNA fluctuates spontaneously over time. The computation of this index using both renal and lumbar SNAs, simultaneously recorded in conscious rats, pointed to a homogenous baroreflex regulation of regional SNAsLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Central CO2 chemoreception and integrated neural mechanisms of cardiovascular and respiratory control

In this review, we ex-amine why blood pressure (BP) and sympathetic nerve activity (SNA) increase during a rise in central nervous system. (CNS) Pco 2 (central chemoreceptor stimulation). CNS acidification modifies SNA by two classes of mechanisms. The first one depends on the activation of the central respiratory controller (CRG) and causes the much-emphasized respiratory modulation of the SNA. The CRG prob-ably modulates SNA at several brain stem or spinal locations, but the most important site of interaction seems to be the caudal ventrolateral medulla (CVLM), where unidentified components of the CRG periodically gate the baroreflex. CNS Pco2 also influences sympathetic tone in a CRG-independent manner, and we propose that this process operates differently according to the level of CNS Pco2. In normocapnia and indeed even below the ventilatory recruitment threshold, CNS Pco2 exerts a tonic concentration-dependent excitatory effect on SNA that is plausibly mediated by specialized brain stem chemoreceptors such as the retrotrap-ezoid nucleus. Abnormally high levels of Pco2 cause an aversive interoceptive awareness in awake individuals and trigger arousal from sleep. These alerting responses presumably activate wake-promoting and/or stress-related pathways such as the orexinergic, noradrenergic, and serotonergic neurons. These neuronal groups, which may also be directly activated by brain acidification, have brainwide projections that contribute to the CO 2-induced rise in breathing and SNA by facilitating neuronal activity at innumerable CNS locations. In the case of SNA, these sites include the nucleus of the solitary tract, the ventrolateral medulla, and the preganglionic neurons.8 page(s

Photostimulation of Phox2b Medullary Neurons Activates Cardiorespiratory Function in Conscious Rats

Rationale: Hypoventilation is typically treated with positive pressure ventilation or, in extreme cases, by phrenic nerve stimulation. This preclinical study explores whether direct stimulation of central chemoreceptors could be used as an alternative method to stimulate breathing