Oswaldo Ubriaco Lopes

Infusions of hyperosmotic NaCl (2,400 mosmol/l; 4 ml/kg) were given to dogs in severe hemorrhagic... more Infusions of hyperosmotic NaCl (2,400 mosmol/l; 4 ml/kg) were given to dogs in severe hemorrhagic hypotension by intravenous injection (72 expts) or intra-aortic injection (25 expts). In 46 experiments intravenous infusions were given during bilateral blockage of the cervical vagal trunks (local anesthesia or cooling). Intravenous infusions (without vagal blockade) restore arterial pressure, cardiac output, and acid-base equilibrium to normal and cause mesenteric flow to overshoot prehemorrhage levels by 50%. These effects are stable, and indefinite survival was observed in every case. Intra-aortic infusions of hyperosmotic NaCl produce only a transient recovery of arterial pressure and cardiac output but no long-term survival. Intravenous infusions with vagal blockage produce only a transient recovery of cardiac output, with non long-term survival. Measurement of pulmonary artery blood osmolarity during and after the infusions shows that a different pattern is observed in each of t...

Mechanism of Hypothalamic Control of Cardiac Component of Sinus Nerve Reflex

Quarterly Journal of Experimental Physiology and Cognate Medical Sciences, 1978

The modulatory influence of hypothalamic structures on sinus nerve induced bradycardia was invest... more The modulatory influence of hypothalamic structures on sinus nerve induced bradycardia was investigated in anaesthetized cats. Stimulation of the hypothalamic defence area inhibits the bradycardia produced by sinus nerve stimulation both in intact animals and also in animals with the spinal cord sectioned at C1 or C6. This inhibition was accompanied in the normal animal by an increased sympathetic discharge and by a sustained inspiration or tachypnoea. The same respiratory effects were noted in a spontaneously breathing C6 spinal animal, while an artificially ventilated C1 spinal animal still displayed a powerful central inspiratory drive in its recurrent laryngeal electroneurogram. The presence of central inspiratory activity was found to be an absolute impediment to the development of bradycardia. If this activity was eliminated by simultaneous stimulation of the superior laryngeal nerve, it was possible to obtain bradycardia during combined sinus nerve and hypothalamic defence area stimulation, though this bradycardia was modified by the presence of sympathetic discharge. The level of sympathetic neural discharge affects the magnitude of the bradycardia produced by sinus nerve stimulation. The bradycardia was less with normal or augmented level of sympathetic activity and was greater if this activity was reduced or absent. A lesion just caudal to the mammillary bodies disclosed a tonic hypothalamic influence both on respiration and on sympathetic discharge; stimulation of the sinus nerve produced a much more powerful bradycardia after the lesion. The existence of a respiratory &quot;gate&quot; through which afferent stimuli pass on their way to the nucleus ambiguus, and which can be operated by the hypothalamic defence and depressor areas, is postulated and discussed.

Cardio-Respiratory Responses During Baroreceptor Stimulation in Neuronal Nitric Oxide Synthase Deficient Mice

Journal of Hypertension, 2004

Respiratory effects of kynurenic acid microinjected into the ventromedullary surface of the rat

Brazilian Journal of Medical and Biological Research, 1998

Several studies demonstrate that, within the ventral medullary surface (VMS), excitatory amino ac... more Several studies demonstrate that, within the ventral medullary surface (VMS), excitatory amino acids are necessary components of the neural circuits involved in the tonic and reflex control of respiration and circulation. In the present study we investigated the cardiorespiratory effects of unilateral microinjections of the broad spectrum glutamate antagonist kynurenic acid (2 nmol/200 nl) along the VMS of urethaneanesthetized rats. Within the VMS only one region was responsive to this drug. This area includes most of the intermediate respiratory area, partially overlapping the rostral ventrolateral medulla (IA/RVL). When microinjected into the IA/RVL, kynurenic acid produced a respiratory depression, without changes in mean arterial pressure or heart rate. The respiratory depression observed was characterized by a decrease in ventilation, tidal volume and mean inspiratory flow and an increase in respiratory frequency. Therefore, the observed respiratory depression was entirely due to a reduction in the inspiratory drive. Microinjections of vehicle (200 nl of saline) into this area produced no significant changes in breathing pattern, blood pressure or heart rate. Respiratory depression in response to the blockade of glutamatergic receptors inside the rostral VMS suggests that neurons at this site have an endogenous glutamatergic input controlling the respiratory cycle duration and the inspiratory drive transmission.

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Efeito hipotensor dos inibidores da enzima de conversao: bradicinina ou prostaglandinas ?

Role of ventrolateral medulla in the maintenance of arterial blood pressure in awake animals

UNIFESP,ESCOLA PAULISTA MED,DEPT PHYSIOL,BR-04023062 SAO PAULO,BRAZILUNIFESP,ESCOLA PAULISTA MED,... more

Cardiovascular responses evoked from the nicotine-sensitive area on the ventral surface of the medulla oblongata in the cat

The Journal of Physiology, 1984

1. Experiments were carried out in cats anaesthetized with chloralose, (a) to examine the effect ... more 1. Experiments were carried out in cats anaesthetized with chloralose, (a) to examine the effect on blood pressure, heart rate and respiratory frequency produced by topical application of leptazol, nicotine and sodium pentobarbitone to the ventral surface of the medulla at an area around the rootlets of the XII cranial nerve, and (b) to study the role of this area in some cardiovascular reflexes. 2. Leptazol applied unior bilaterally to this area produced hypotension, bradycardia and bradypnoea. 3. The area from which leptazol produced these effects was localized 3-6 mm lateral to the mid line and 5-9 mm caudal to the lower border of the trapezoid bodies. 4. When comparing the effects of leptazol and nicotine applied to this area it was found that in concentrations that produced similar falls in arterial blood pressure and heart rate leptazol produced a much stronger bradypnoea than nicotine. 5. The hypotension produced by leptazol was mainly due to inhibition of sympathetic vasomotor tone since it was little affected by section of the vagi and by atropine given intravenously. 6. Bilateral application of sodium pentobarbitone produced a small hypertension, tachycardia and pronounced tachypnoea. Unilateral application of sodium pentobarbitone had no effect by itself but inhibited the effects of leptazol applied to the same site. 7. Cardiovascular reflexes produced by sinus nerve stimulation, by increased sinus pressure or by injections of veratridine into a vein or into the left ventricle of the heart were potentiated by topical application of leptazol to the ventral surface and depressed by the topical application of sodium pentobarbitone. 8. The chemoreceptor reflex, produced by retrograde injections of lobeline into the lingual artery, was partially affected by topical application ofsodium pentobarbitone: the evoked bradyeardia was attenuated but the tachypnoea and hypertension were not affected. 9. These results suggest that this medullary area on the ventral surface of the medulla plays an important role in normal cardiovascular regulation.

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Efeito da indometacina, ibuprofeno e aspirina sobre o crescimento tumoral e caquexia de ratos portadores do tumor de Walker 256

Resumos, 1989