The role of testosterone in the respiratory and thermal responses to hypoxia and hypercapnia in rats.

Many diseases of the respiratory system occur differently in males and females, indicating a possible role of gonadal hormones in respiratory control. We hypothesized that testosterone (T) is important for the ventilatory chemosensitivity responses in males. To test this hypothesis, we evaluated ventilation (V̇ E), metabolic rate and body temperature (Tb) under normoxia/normocapnia, hypercapnia and hypoxia in orchiectomized (ORX), ORX with testosterone replacement (ORX + T) or flutamide (FL, androgen receptor blocker)-treated rats. We also performed immunohistochemistry to evaluate the presence of androgen receptor (AR) in the carotid body (CB) of intact males. Orchiectomy promoted a reduction V̇ E and ventilatory equivalent (V̇ E /V̇ O2) under room-air conditions, which was restored with testosterone treatment. Moreover, during hypoxia or hypercapnia, animals that received testosterone replacement had a higher V̇ E and V̇ E /V̇ O2 than control and ORX, without changes in metabolic and thermal variables. Flutamide decreased the hypoxic ventilatory response without changing the CO2-drive to breathe, suggesting that the testosterone effect on hypercapnic hyperventilation does not appear to involve the AR. We also determined the presence of AR in the CB of intact animals. Our findings demonstrate that testosterone seems to be important for maintaining resting V̇ E in males. In addition, the influence of testosterone on V̇ E, either during resting conditions or under hypoxia and hypercapnia, seems to be a direct and specific effect, as no changes in metabolic rate or Tb were observed during any treatment. Finally, a putative site of testosterone action during hypoxia is the CB, since we detected the presence of AR in this structure.

Carotid body chemoreceptors, sympathetic neural activation, and cardiometabolic disease.

The carotid body (CB) is the main peripheral chemoreceptor that senses the arterial PO2, PCO2 and pH. In response to hypoxemia, hypercapnia and acidosis, carotid chemosensory discharge elicits reflex respiratory, autonomic and cardiovascular adjustments. The classical construct considers the CB as the main peripheral oxygen sensor, triggering reflex physiological responses to acute hypoxemia and facilitating the ventilatory acclimation to chronic hypoxemia at high altitude. However, a growing body of experimental evidence supports the novel concept that an abnormally enhanced CB chemosensory input to the brainstem contributes to overactivation of the sympathetic nervous system, and consequent pathology. Indeed, the CB has been implicated in several diseases associated with increases in central sympathetic outflow. These include hypertension, heart failure, sleep apnea, chronic obstructive pulmonary disease and metabolic syndrome. Indeed, ablation of the CB has been proposed for the treatment of severe and resistant hypertension in humans. In this review, we will analyze and discuss new evidence supporting an important role for the CB chemoreceptor in the progression of autonomic and cardiorespiratory alterations induced by heart failure, obstructive sleep apnea, chronic obstructive pulmonary disease and metabolic syndrome.

Carotid body Thermoreceptors, sympathetic neural activation, and cardiometabolic disease

The carotid body (CB) is the main peripheral chemoreceptor that senses the arterial PO2, PCO2 and pH. In response to hypoxemia, hypercapnia and acidosis, carotid chemosensory discharge elicits reflex respiratory, autonomic and cardiovascular adjustments. The classical construct considers the CB as the main peripheral oxygen sensor, triggering reflex physiological responses to acute hypoxemia and facilitating the ventilatory acclimation to chronic hypoxemia at high altitude. However, a growing body of experimental evidence supports the novel concept that an abnormally enhanced CB chemosensory input to the brainstem contributes to overactivation of the sympathetic nervous system, and consequent pathology. Indeed, the CB has been implicated in several diseases associated with increases in central sympathetic outflow. These include hypertension, heart failure, sleep apnea, chronic obstructive pulmonary disease and metabolic syndrome. Indeed, ablation of the CB has been proposed for the treatment of severe and resistant hypertension in humans. In this review, we will analyze and discuss new evidence supporting an important role for the CB chemoreceptor in the progression of autonomic and cardiorespiratory alterations induced by heart failure, obstructive sleep apnea, chronic obstructive pulmonary disease and metabolic syndrome.

Estudio comparativo con doppler triplex y scion image® del sistema carotideo extracraneal / Comparative study with doppler triplex and scion image® of the carotid extracranial system

Comparar Doppler Triplex y Scion Image® para obtener un análisis computarizado de la ecogenicidadque caracteriza cualitativamente a los tejidos estudiados en las imágenes médicas adquiridas. Se examinó la región cervical bilateralmente a una muestra de individuos adultos jóvenes de ambos sexos. Se procedió a realizar un histograma computarizado en una región de interés seleccionada al azar de la arteria carótida común y del músculo esternocleidomastoideo, analizando los datos obtenidos con el método estadístico HOMALS. Se observó que la mediana para los valores altos y bajos en la escala de gris de la arteria carótida común y del músculo esternocleidomastoideo, tiene similitud con la de los valores altos y bajos de la velocidad pico sistólica de la arteria carótida común. Asimismo, la mediana de las variables categóricas correspondientes a la escala de gris de la arteria carótida común y del músculo esternocleidomastoideo, también tiene similitud con la de los valores de la velocidad al final de la diástole de la arteria carótida común. La comparación de Doppler Triplex con Scion Image® es factible, resultando estadísticamente discriminante para el estudio del sistema carotídeo extracraneal.

To compare Doppler Triplex and Scion Image® to obtain a computed analysis of the echogenicity that qualitatively characterizes to the tissues studied in the acquired medical images. It was examined the cervical region bilaterally to a sample of young mature individuals of both sexes. It was proceeded to carry out an computed histogram in a region of interest selected at random of the common carotid artery and the sternomastoid muscle, analyzing the obtained data with the statistical method HOMALS. It was observed that the median for the upper and under values in the grayscale of the common carotid artery and of the sternomastoid muscle, this has similarity with that of the upper and under values of the peak systolic velocity of the common carotid artery. Also, it could be appreciated that the median of the values of the categorical variables corresponding to the grayscale of the common carotid artery and of the sternomastoid muscle, this also has similarity with that of the peak end diastolic velocity of the common carotid artery. The comparison of Doppler Triplex with Scion Image® is feasible, being statistically discriminant for the study of the extracranial carotid system.

Glutamate in the glomus cells of the cat carotid body: immunocytochemistry and in vitro release.

The identity of the postulated excitatory transmitter released by glomus cells is not known. Since our preliminary work on paraffin sections of the cat carotid body indicated that most glomus cells were intensely immunoreactive to glutamate, we decided to investigate whether glutamate might be such a transmitter, using two approaches. One approach was to make a quantitative immunogold analysis of ultrathin sections to assess the level of glutamate immunoreactivity of glomus cells relative to glia and to afferent axon terminals. The other approach was to measure the potassium-induced release of glutamate from carotid bodies superfused in vitro. We consistently found that glomus cell profiles had 50% more immunogold particles per unit of area than glial cell or axonal profiles. However, the levels of glutamate immunoreactivity of glomus cells were lower than those expected for glutamatergic terminals. We also found that glutamate was not released from in vitro carotid bodies stimulated with high concentrations of potassium. These findings indicate that the oxygen-sensitive glomus cells have a high concentration of glutamate, which is not released by superfusion with high potassium. Thus, glutamate is not the excitatory transmitter released by glomus cells. We speculate that the high concentrations of glutamate might instead be related to the known dependence of the "in vitro" chemosensory activity on metabolic substrates.