Serotonergic mechanisms on breathing modulation in the rat locus coeruleus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

5-HT1A, but not 5-HT2 and 5-HT7, receptors in the nucleus raphe magnus modulate hypoxia-induced hyperpnoea

Aim: In the present study, we assessed the role of 5-hydroxytryptamine (5-HT) receptors (5-HT1A, 5-HT2 and 5-HT7) in the nucleus raphe magnus (NRM) on the ventilatory and thermoregulatory responses to hypoxia.Methods: To this end, pulmonary ventilation (V-E) and body temperature (T-b) of male Wistar rats were measured in conscious rats, before and after a 0.1 mu L microinjection of WAY-100635 (5-HT1A receptor antagonist, 3 mu g 0.1 mu L-1, 56 mM), ketanserin (5-HT2 receptor antagonist, 2 mu g 0.1 mu L-1, 36 mM) and SB269970 (5-HT7 receptor antagonist, 4 mu g 0.1 mu L-1, 103 mM) into the NRM, followed by 60 min of severe hypoxia exposure (7% O-2).Results: Intra-NMR microinjection of vehicle (control rats) or 5-HT antagonists did not affect V-E or T-b during normoxic conditions. Exposure of rats to 7% O-2 evoked a typical hypoxia-induced anapyrexia after vehicle microinjections, which was not affected by microinjection of WAY-100635, SB269970 or ketanserin. The hypoxia-induced hyperpnoea was not affected by SB269970 and ketanserin intra-NMR. However, the treatment with WAY-100635 intra-NRM attenuated the hypoxia-induced hyperpnoea.Conclusion: These data suggest that 5-HT acting on 5-HT1A receptors in the NRM increases the hypoxic ventilatory response.

Respiratory chemoreceptor function in vertebrates - Comparative and evolutionary aspects

The sensing of blood gas tensions and/or pH is an evolutionarily conserved, homeostatic mechanism, observable in almost all species studied from invertebrates to man. In vertebrates, a shift from the peripheral O2-oriented sensing in fish, to the central CO2/pH sensing in most tetrapods reflects the specific behavioral requirements of these two groups whereby, in teleost fish, a highly O2-oriented control of breathing matches the ever-changing and low oxygen levels in water, whilst the transition to air-breathing increased the importance of acid-base regulation and O2-related drive, although retained, became relatively less important. The South American lungfish and tetrapods are probably sister groups, a conclusion backed up by many similar features of respiratory control. For example, the relative roles of peripheral and central chemoreceptors are present both in the lungfish and in land vertebrates. In both groups, the central CO2/pH receptors dominate the ventilatory response to hypercarbia (60-80), while the peripheral CO2/pH receptors account for 20-30. Some basic components of respiratory control have changed little during evolution. This review presents studies that reflect the current trends in the field of chemoreceptor function, and several laboratories are involved. An exhaustive review on the previous literature, however, is beyond the intended scope of the article. Rather, we present examples of current trends in respiratory function in vertebrates, ranging from fish to humans, and focus on both O2 sensing and CO2 sensing. As well, we consider the impact of chronic levels of hypoxia - a physiological condition in fish and in land vertebrates resident at high elevations or suffering from one of the many cardiorespiratory disease states that predispose an animal to impaired ventilation or cardiac output. This provides a basis for a comparative physiology that is informative about the evolution of respiratory functions in vertebrates and about human disease. Currently, most detail is known for mammals, for which molecular biology and respiratory physiology have combined in the discovery of the mechanisms underlying the responses of respiratory chemoreceptors. Our review includes new data on nonmammalian vertebrates, which stresses that some chemoreceptor sites are of ancient origin.

Respostas respiratórias à hipóxia e hipercapnia de frangos de corte provenientes de ovos incubados em diferentes temperaturas

Pós-graduação em Zootecnia - FCAV

Cardiorespiratory effects of gap junction blockade in the locus coeruleus in unanesthetized adult rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Age and gender influence the cardiorespiratory function and metabolic rate of broiler chicks during normocapnia and hypercapnia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Alterações metabólicas e morfométricas induzidas por hipóxia em Gallus gallus

Pós-graduação em Zootecnia - FCAV

Neurochemical and electrical modulation of the locus coeruleus: contribution to CO2drive to breathe

The locus coeruleus (LC) is a dorsal pontine region, situated bilaterally on the floor of the fourth ventricle. It is considered to be the major source of noradrenergic innervation in the brain. These neurons are highly sensitive to CO2/pH, and chemical lesions of LC neurons largely attenuate the hypercapnic ventilatory response in unanesthetized adult rats. Developmental dysfunctions in these neurons are linked to pathological conditions such as Rett and sudden infant death syndromes, which can impair the control of the cardio-respiratory system. LC is densely innervated by fibers that contain glutamate, serotonin, and adenosine triphosphate, and these neurotransmitters strongly affect LC activity, including central chemoreflexes. Aside from neurochemical modulation, LC neurons are also strongly electrically coupled, specifically through gap junctions, which play a role in the CO2 ventilatory response. This article reviews the available data on the role of chemical and electrical neuromodulation of the LC in the control of ventilation.

Neuroglia and their roles in central respiratory control; an overview

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ventilatory responses to skin extract in catfish

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Caution for using ventilatory frequency as an indicator of stress in fish

This study tested the use of ventilatory frequency (VF) as an indicator of stress in the Nile tilapia, Oreochromis niloticus (L.). Firstly, we tested the relationship between VF and plasma cortisol after confinement. Confined fish showed higher VF and plasma cortisol levels, but the latter continued to increase significantly for longer time than VF. Secondly, we conducted another experiment to test the use of VF as indicator of fish stress. In four out of six treatment, we confined the fish for different intervals (30 s, 5, 15 or 30 min). The others were used as control. In one, no handling was imposed. The other control consisted of introducing the partition (the same used to perform the confinement) into the aquarium for less than 4 s, without confinement and immediately removing the partition (partition control). Ventilatory frequency was increased for the partition control as much as for the longer duration of confinement. This clearly indicates that VF is a very sensitivity response to disturbance, but of limited use because this parameter does not reflect the severity of the stimulus. Thus, although VF is a non-invasive technique that does not require sophisticated recording equipment, its usefulness is limited. (C) 2004 Elsevier B.V. All rights reserved.

Ventilatory compensation of the alkaline tide during digestion in the snake Boa constrictor

The increased metabolic rate during digestion is associated with changes in arterial acid-base parameters that are caused by gastric acid secretion (the 'alkaline tide'). Net transfer of HCl to the stomach lumen causes an increase in plasma HCO3- levels, but arterial pH does not change because of a ventilatory compensation that counters the metabolic alkalosis. It seems, therefore, that ventilation is controlled to preserve pH and not P-CO2, during the postprandial period. To investigate this possibility, we determined arterial acid-base parameters and the metabolic response to digestion in the snake Boa constrictor, where gastric acid secretion was inhibited pharmacologically by oral administration of omeprazole. The increase in oxygen consumption of omeprazole-treated snakes after ingestion of 30% of their own body mass was quantitatively similar to the response in untreated snakes, although the peak of the metabolic response occurred later (36 h versus 24 h). Untreated control animals exhibited a large increase in arterial plasma HCO3- concentration of approximately 12 mmol 1(-1), but arterial pH only increased by 0.12 pH units because of a simultaneous increase in arterial P-CO2 by about 10 mmHg. Omeprazole virtually abolished the changes in arterial pH and plasma HCO3- concentration during digestion and there was no increase in arterial P-CO2. The increased arterial P-CO2 during digestion is not caused, therefore, by the increased metabolism during digestion or a lower ventilatory responsiveness to ventilatory stimuli during a presumably relaxed state in digestion. Furthermore, the constant arterial P-CO2, in the absence of an alkaline tide, of omeprazole-treated snakes strongly suggests that pH rather than P-CO2 normally affects chemoreceptor activity and ventilatory drive.

Ventilatory frequency of Nile tilapia subjected to different stressors

Ventilatory frequency (VF) was investigated in the fish Nile tilapia, Oreochromis niloticus, subjected to confinement, electroshock or social stressor. Fish were allowed to acclimatize to tank conditions for 10 days (1 fish/aquarium). VF baseline was determined 5 days after adjustment had been started. At the 10th day of isolation, stressor effects on VF were assessed. The stressors were imposed during 60 min: pairing with a larger resident animal (social stressor), or gentle electroshock (AC, 20 V, 15 mA, 100 Hz for 1 min every 4 min), or space restriction (confinement). VF was quantified immediately after the end of the stressor imposition. Baseline of VF was not statistically different among groups. Social stressor clearly induced VF to increase, while an increased or decreased VF can be observed for both confinement and electroshock. However, fish tend to increase their VF in response to confinement and decrease in the case of electroshock. These results suggest that VF is a sensitive behavioural indicator for distinguishing stress responses in the fish Nile tilapia among different stressors. © 2006 Elsevier GmbH. All rights reserved.

Environmental light color affects the stress response of Nile tilapia

We investigated the effects of environmental light colors (blue, yellow and white) on the stress responses (measured by changes in ventilatory frequency - VF) of Nile tilapia to confinement. After 7 days of light treatment, the VF was similar for fish in each color. On the 8th day, fish were confined for 15. min. After release, the post-confinement VF was measured six times (first period: 0, 2 and 4. min; second period: 6, 8 and 10. min). Irrespective of the light color treatment, confinement increased the VF to higher levels during the first post-confinement period than during the second one. When color was analyzed, irrespective of time, fish under white light increased their VF post-confinement, and blue light prevented this effect. We conclude that blue light is the preferred color for Nile tilapia in terms of reducing stress. This finding is in contrast to previous choice test studies that indicated that yellow is their preferred color. © 2012 Elsevier GmbH.

Branchial O2 chemoreceptors in Nile tilapia Oreochromis niloticus: Control of cardiorespiratory function in response to hypoxia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)