- Facultad de Ciencias
Universidad de Chile
Las Palmeras 3425
Edificio Biología-Milenio - +56229787366
Julio Alcayaga
Universidad de Chile, Departamento de Biología, Faculty Member
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Emergent evidence indicates that the carotid body (CB) chemoreceptor may sense systemic inflammatory molecules and is an afferent arm of the anti-inflammatory reflex. Moreover, a proinflammatory milieu within the CB is involved in the... more
Emergent evidence indicates that the carotid body (CB) chemoreceptor may sense systemic inflammatory molecules and is an afferent arm of the anti-inflammatory reflex. Moreover, a proinflammatory milieu within the CB is involved in the enhanced CB chemosensory responsiveness to oxygen following sustained and intermittent hypoxia. In this review, we focus on the physiopathological participation of CBs in inflammatory diseases, such as sepsis and intermittent hypoxia.
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The carotid body (CB) is the main peripheral chemoreceptor for arterial respiratory gases O2 and CO2 and pH, eliciting reflex ventilatory, cardiovascular, and humoral responses to maintain homeostasis. This review examines the fundamental... more
The carotid body (CB) is the main peripheral chemoreceptor for arterial respiratory gases O2 and CO2 and pH, eliciting reflex ventilatory, cardiovascular, and humoral responses to maintain homeostasis. This review examines the fundamental biology underlying CB chemoreceptor function, its contribution to integrated physiological responses, and its role in maintaining health and potentiating disease. Emphasis is placed on 1) transduction mechanisms in chemoreceptor (type I) cells, highlighting the role played by the hypoxic inhibition of O2-dependent K+ channels and mitochondrial oxidative metabolism, and their modification by intracellular molecules and other ion channels; 2) synaptic mechanisms linking type I cells and petrosal nerve terminals, focusing on the role played by the main proposed transmitters and modulatory gases, and the participation of glial cells in regulation of the chemosensory process; 3) integrated reflex responses to CB activation, emphasizing that the responses differ dramatically depending on the nature of the physiological, pathological, or environmental challenges, and the interactions of the chemoreceptor reflex with other reflexes in optimizing oxygen delivery to the tissues; and 4) the contribution of enhanced CB chemosensory discharge to autonomic and cardiorespiratory pathophysiology in obstructive sleep apnea, congestive heart failure, resistant hypertension, and metabolic diseases and how modulation of enhanced CB reactivity in disease conditions may attenuate pathophysiology.
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Activation of the sympathetic nervous system is a hallmark of heart failure (HF) and is positively correlated with disease progression. Catecholaminergic (C1) neurons located in the rostral ventrolateral medulla (RVLM) are known to... more
Activation of the sympathetic nervous system is a hallmark of heart failure (HF) and is positively correlated with disease progression. Catecholaminergic (C1) neurons located in the rostral ventrolateral medulla (RVLM) are known to modulate sympathetic outflow and are hyperactivated in volume overload HF. However, there is no conclusive evidence showing a contribution of RVLM-C1 neurons to the development of cardiac dysfunction in the setting of HF. Therefore, the aim of this study was to determine the role of RVLM-C1 neurons in cardiac autonomic control and deterioration of cardiac function in HF rats. A surgical arteriovenous shunt was created in adult male Sprague-Dawley rats to induce HF. RVLM-C1 neurons were selectively ablated using cell-specific immunotoxin (dopamine-β hydroxylase saporin [DβH-SAP]) and measures of cardiac autonomic tone, function, and arrhythmia incidence were evaluated. Cardiac autonomic imbalance, arrhythmogenesis and cardiac dysfunction were present in HF...
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The carotid bodies (CBs) of the cat are excited by occlusions of the common carotids (1), resulting in reflex hyperventilation (2). The CBs are also responsive to systemic hypotension, although less than the aortic bodies are (3). When... more
The carotid bodies (CBs) of the cat are excited by occlusions of the common carotids (1), resulting in reflex hyperventilation (2). The CBs are also responsive to systemic hypotension, although less than the aortic bodies are (3). When perfused in situ with either blood or saline, the CBs are excited rapidly by flow arrest, a phenomenon reversed shortly after flow restoration (4). Single or few fiber recordings of carotid (sinus) nerve activity show that all chemosensory units respond transiently to changes in perfusion pressure in the opposite direction to the pressure change (5,6), while nearly one-third of them also respond to steady levels of perfusion pressure (5,7). Because of the high blood flow through the CB (8) and its dependence on systemic arterial pressure (9), it has been suggested that these chemosensory responses may be mediated, at least in part, by reduced flow to the CB parenchyma.
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doi: 10.3389/fncel.2014.00158 Opening of pannexin- and connexin-based channels increases the excitability of nodose ganglion sensory neurons
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Monitoring soil water content together with plant-monitoring techniques have proved to be very good management tools for making irrigation decisions in avocado orchards. There are many well-tested devices for monitoring soil moisture... more
Monitoring soil water content together with plant-monitoring techniques have proved to be very good management tools for making irrigation decisions in avocado orchards. There are many well-tested devices for monitoring soil moisture content in orchards, but options for measuring plant water status are limited. The objective of this study was to determine if measuring variations in electrical voltage differences between roots and leaves can be used as a plant-monitoring technique related to soil water content. Root and shoot voltages differences were monitored in two-year-old ‘Hass ’ avocado trees grafted onto Duke 7 rootstocks in a laboratory. Root and shoot voltages differences were initially measured for about 2 hours in unaltered trees to determine steady state (control) conditions. Plants were then exposed to cycles of soil (root) drying and re-watering. The extracellular electrical potential difference between the base of the trunk and the leaf petiole was continuously monitor...
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In spontaneously breathing, pentobarbitone anesthetized cats, we recorded simultaneously the impulses in the chemosensory fibers of both carotid (sinus) nerves, to analyze the correlations between the frequencies of chemosensory... more
In spontaneously breathing, pentobarbitone anesthetized cats, we recorded simultaneously the impulses in the chemosensory fibers of both carotid (sinus) nerves, to analyze the correlations between the frequencies of chemosensory discharges (f chi) and their activation (¿df chi/dt¿a) and deactivation (¿df chi/dt¿d) rates. We studied the chemosensory responses to brief exposures to hypoxia (100% N2; 5-s and 10-s) and hyperoxia (100% O2; 30-s), and intravenous injections of excitatory (NaCN 0.2-100 micrograms/kg) and inhibitory (dopamine hydrochloride 0.02-20 micrograms/kg) chemoreceptor agents. Hypoxia increased f chi, with a high temporal correlation between frequency levels in both nerves. Prolonging hypoxic stimulation increased ¿df chi/dt¿d, with preservation of ¿df chi/dt¿a. Hyperoxic exposure produced highly correlated decreases in f chi in both nerves, but reduced correlation in df chi/dt. Increasing doses of NaCN produced analogous increments in f chi, df chi/dt and their corr...
Research Interests: Medicine, Cats, Biological Sciences, Anoxia, Animals, and 6 moreMale, Biological, Carotid Sinus, Time Factors, Carotid Body, and Hyperoxia
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The carotid body (CB) is the main arterial chemoreceptor involved in oxygen sensing. Upon hypoxic stimulation, CB chemoreceptor cells release neurotransmitters, which increase the frequency of action potentials in sensory nerve fibers of... more
The carotid body (CB) is the main arterial chemoreceptor involved in oxygen sensing. Upon hypoxic stimulation, CB chemoreceptor cells release neurotransmitters, which increase the frequency of action potentials in sensory nerve fibers of the carotid sinus nerve. The identity of the molecular entity responsible for oxygen sensing is still a matter of debate; however several ion channels have been shown to be involved in this process. Connexin-based ion channels are expressed in the CB; however a definitive role for these channels in mediating CB oxygen sensitivity has not been established. To address the role of these channels, we studied the effect of blockers of connexin-based ion channels on oxygen sensitivity of the CB. A connexin43 (Cx43) hemichannel blocking agent (CHBa) was applied topically to the CB and the CB-mediated hypoxic ventilatory response (FO 21, 15, 10 and 5%) was measured in adult male Sprague-Dawley rats (~250 g). In normoxic conditions, CHBa had no effect on tid...
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The carotid body (CB) chemoreceptors sense changes in arterial blood gases. Upon stimulation CB chemoreceptors cells release one or more transmitters to excite sensory nerve fibers of the carotid sinus nerve. While several... more
The carotid body (CB) chemoreceptors sense changes in arterial blood gases. Upon stimulation CB chemoreceptors cells release one or more transmitters to excite sensory nerve fibers of the carotid sinus nerve. While several neurotransmitters have been described to contribute to the CB chemosensory process less is known about modulatory molecules. Recent data suggest that erythropoietin (Epo) is involved in the control of ventilation, and it has been shown that Epo receptor is constitutively expressed in the CB chemoreceptors, suggesting a possible role for Epo in regulation of CB function. Therefore, in the present study we aimed to determine whether exogenous applications of Epo modulate the hypoxic and hypercapnic CB chemosensory responses. Carotid sinus nerve discharge was recorded in-situ from anesthetized adult male and female Sprague Dawley rats (350 g, n = 8) before and after systemic administration of Epo (2000 UI/kg). CB-chemosensitivity to hypoxia and hypercapnia was calcul...
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In this review article, we summarize the current insight on the role of Connexin- and Pannexin-based channels as modulators of sensory neurons. The somas of sensory neurons are located in sensory ganglia (i.e., trigeminal and nodose... more
In this review article, we summarize the current insight on the role of Connexin- and Pannexin-based channels as modulators of sensory neurons. The somas of sensory neurons are located in sensory ganglia (i.e., trigeminal and nodose ganglia). It is well known that within sensory ganglia, sensory neurons do not form neither electrical nor chemical synapses. One of the reasons for this is that each soma is surrounded by glial cells, known as satellite glial cells (SGCs). Recent evidence shows that connexin43 (Cx43) hemichannels and probably pannexons located at SGCs have an important role in paracrine communication between glial cells and sensory neurons. This communication may be exerted via the release of bioactive molecules from SGCs and their subsequent action on receptors located at the soma of sensory neurons. The glio-neuronal communication seems to be relevant for the establishment of chronic pain, hyperalgesia and pathologies associated with tissue inflammation. Based on the ...
Neurons from many brain regions display intrinsic subthreshold theta-resonance, responding preferentially to theta-frequency oscillatory stimuli. Resonance may contribute to selective communication among neurons and to orchestrate brain... more
Neurons from many brain regions display intrinsic subthreshold theta-resonance, responding preferentially to theta-frequency oscillatory stimuli. Resonance may contribute to selective communication among neurons and to orchestrate brain rhythms. CA1 pyramidal neurons receive theta activity, generating place fields. In these neurons the expression of perithreshold frequency preference is controversial, particularly in the spiking regime, with evidence favoring either non-resonant (integrator-like) or resonant behavior. Perithreshold dynamics depends on the persistent Na(+) current INaP developing above -70 mV and the muscarine-sensitive K(+) current IM activating above -60 mV. We conducted current and voltage clamp experiments in slices to investigate perithreshold excitability of CA1 neurons under oscillatory stimulation. Around 20% of neurons displayed perithreshold resonance that is expressed in spiking. The remaining neurons (~80%) acted as low-pass filters lacking frequency pref...
To test the effect of combined intermittent hypoxia (IH) and body weight-supported treadmill training (BWSTT) on standing and dynamic balance in persons with incomplete spinal cord injury (iSCI). Randomized, triple-blind,... more
To test the effect of combined intermittent hypoxia (IH) and body weight-supported treadmill training (BWSTT) on standing and dynamic balance in persons with incomplete spinal cord injury (iSCI). Randomized, triple-blind, placebo-controlled study. Rehabilitation medical centers. Study participants (N=35) with chronic iSCI with American Spinal Injury Association grades C and D (>1y postinjury) were randomly assigned to either IH plus BWSTT (n=18) or continued normoxia (placebo) plus BWSTT protocol (n=17). Participants received either IH (alternating 1.5min 9% inspired O2 with 1.5min 21% inspired O2, 15 cycles per day) or continued normoxia (21% O2) combined with 45 minutes of BWSTT for 5 consecutive days, followed by 3 times per week IH or normoxia plus BWSTT, for 3 additional weeks. Standing balance (normalized jerk and root-mean-square [RMS]) and dynamic balance (turning duration, cadence in a turn, and turn-to-sit duration) were assessed before and after IH and normoxia protocol by means of instrumented sway and instrumented timed Up and Go test. There was no significant difference in standing balance between interventions for both normalized jerk and RMS instrumented sway components (both P>.05). There was a significantly faster cadence (P<.001), turning duration (P<.001), and turn-to-sit duration (P=.001) in subjects receiving IH plus BWSTT, compared with placebo. A 4-week protocol of IH combined with locomotor training improves dynamic, but not standing, balance in persons with iSCI.
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Ventilation is peripherally controlled by afferent activity arising from the peripheral chemoreceptors. In the rat, chemosensory activity is conveyed to the central nervous system through axons of neurons located in the... more
Ventilation is peripherally controlled by afferent activity arising from the peripheral chemoreceptors. In the rat, chemosensory activity is conveyed to the central nervous system through axons of neurons located in the nodose-petrosal-jugular-complex. These neurons have distinct electrophysiological properties, including a persistent Na(+) current. Acute blockade of this current with phenytoin and other anti-epileptic drugs reduces normoxic chemosensory activity and responses to acute hypoxia. However, because anti-epileptic therapy is prolonged and there is no information on the effects of chronic phenytoin treatment on peripheral chemosensory activity, we studied the effects of long-lasting phenytoin treatment (~25 days) on afferent chemosensory activity, on a wide range of oxygen inspiratory fractions. Osmotic pumps containing dissolved phenytoin (166mg/mL) or vehicle (daily flow: 60μL) were implanted subcutaneously in male adult Sprague Dawley rats. At the end of the treatment,...
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The carotid body (CB) is the main peripheral chemoreceptor. The present model of CB chemoreception states that glomus (type I) cells are the primary receptors, which are synaptically connected to the nerve terminals of the petrosal... more
The carotid body (CB) is the main peripheral chemoreceptor. The present model of CB chemoreception states that glomus (type I) cells are the primary receptors, which are synaptically connected to the nerve terminals of the petrosal ganglion neurons. In response to hypoxia, hypercapnia and acidosis, glomus cells release one (or more) transmitter(s) which, acting on the nerve terminals of chemosensory neurons, increases the afferent discharge. Among several molecules present in glomus cells, dopamine, acetylcholine and 5'-adenosine-triphosphate have been proposed to be the excitatory transmitters in the CB. Beside these putative excitatory transmitters, other molecules modulate the chemosensory process through direct actions on glomus cells and/or by producing tonic effects on CB blood vessels. In this review, we focus on the role played by dopamine in the CB chemoreception, with emphasis on the open question if the reported differences on its actions on the generation of afferent chemosensory activity reflect true species differences. The available data suggest that dopamine may play a modulatory role within the cat CB, while in the rabbit CB, dopamine is an excitatory transmitter. Therefore, the reported differences on the actions of exogenously applied dopamine and its participation on the generation of afferent chemosensory activity appear to reflect true species differences.
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Incomplete spinal cord injuries (iSCI) leave spared synaptic pathways below the level of injury. Intermittent hypoxia (IH) elicits plasticity in the spinal cord and strengthens spared synaptic pathways, expressed as respiratory and... more
Incomplete spinal cord injuries (iSCI) leave spared synaptic pathways below the level of injury. Intermittent hypoxia (IH) elicits plasticity in the spinal cord and strengthens spared synaptic pathways, expressed as respiratory and somatic functional recovery in experimental animals and humans with iSCI. This study corresponds to a randomized, triple-blind, two-arm parallel clinical trial performed in Santiago, Chile. We compared the effects of a 4-week protocol of IH combined with body weight-supported treadmill training (BWSTT), with continuous normoxia (Nx) and BWSTT on 10-meter walk test (10MWT), 6-minute walk test (6MWT), and timed up and go (TUG) test in ASIA C and D individuals with iSCI. Subjects received daily IH (cycling 9%/21% O2 every 1.5 min, 15 cycles/day) or continuous Nx (21% O2) combined with 45 minutes BWSTT for 5 consecutive days, followed by IH/Nx 3x per week (3xwIH/Nx) for 3 additional weeks. Subjects were assessed at day 5, weekly from weeks 2-4, and at a 2-week follow-up. Daily IH plus BWSTT enhanced walking speed, expressed as decreased 10MWT time at day 5 versus baseline (IH:-10.2±3.0 vs. Nx:-1.7±1.7 s, P=0.006), and walking endurance expressed as increased 6MWT distance at day 5 versus baseline (IH: 43.0±10.7 vs. Nx: 6.1±3.4 m, P=0.012), but not TUG time. Further, 3xwIH maintained the daily IH-induced walking speed, and enhanced the daily IH-induced walking endurance, which is maintained up to the 2-week follow-up. We conclude that daily IH enhances walking recovery in subjects with iSCI, confirming prior findings. Moreover, 3xwIH prolonged or enhanced daily IH-induced walking speed and endurance improvements, respectively, up to 5 weeks post daily IH. Repetitive IH may be a safe and effective therapeutic alternative for individuals with iSCI.
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Research Interests: Psychology, Cognitive Science, Nonparametric Statistics, Hypoxia, Exercise therapy, and 14 moreHumans, Female, Male, Young Adult, Aged, Middle Aged, Adult, Memory Disorders, Spinal Cord Injuries, Neurosciences, Verbal Learning, Neuropsychological Tests, Recovery of Function, and Outcome assessment (Health care)
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The effects of common carotid artery occlusions on the afferent activity recorded from the carotid (sinus) nerve were studied in 20 pentobarbitone anesthetized cats. Ipsilateral occlusions lowered intrasinusal pressure down to 15-100... more
The effects of common carotid artery occlusions on the afferent activity recorded from the carotid (sinus) nerve were studied in 20 pentobarbitone anesthetized cats. Ipsilateral occlusions lowered intrasinusal pressure down to 15-100 torr, depending on previous pressures, and resulted in silencing of carotid barosensory impulses. For cats breathing room air and with mean systemic arterial pressure below 125 torr, chemosensory excitation was induced whenever these occlusions lasted 5 sec or longer and it persisted during 10 min occlusions. The chemosensory excitation had a delay of about 4 sec and the maximal frequency of discharges was attained at nearly 30 sec, followed by a maintained submaximal level of about 80-90% of the peak frequency. For ipsilateral occlusions performed under 100% O2 inhalation, the delay of the excitation was increased to ca. 20 sec and the maximal frequency attained only 30-40% of that obtained for the same animal when breathing room air. Bilateral occlusions caused deeper falls in intrasinusal pressure and stronger chemoreceptor excitation. When arterial pressure was above 130 torr, ipsilateral occlusions only produced transient increases in chemosensory discharges or suppression of their ventilatory fluctuations. Chemical stimuli further increased chemosensory frequency during occlusions, indicating that blood flow through carotid body was not arrested. It is concluded that occlusions of the common carotid may induce an increased frequency of carotid chemosensory discharges. This increment is dependent on systemic arterial pressure, ventilatory conditions and duration of the occlusion. It is suggested that the increased carotid chemosensory activity may interact with the withdrawal of barosensory discharges to elicit the reflex changes observed during carotid occlusions.
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The effects evoked by 1 min occlusions of the common carotids were studied in 16 spontaneously breathing pentobarbitone anesthetized cats. Unilateral occlusions induced increases in systemic arterial pressure (to 111.5% of basal), but no... more
The effects evoked by 1 min occlusions of the common carotids were studied in 16 spontaneously breathing pentobarbitone anesthetized cats. Unilateral occlusions induced increases in systemic arterial pressure (to 111.5% of basal), but no changes in ventilation. Bilateral occlusions provoked larger increases in systemic arterial pressure (to 137.5% of basal) and mild tachycardia, associated with pulmonary and alveolar hyperventilation. Breath-by-breath minute volume augmented (to an averaged maximum of 144.7% of basal), the increase in tidal volume being more important than that of respiratory frequency. The maximal changes occurred shortly after occlusion and they were inversely but not linearly related to the minimal levels of intrasinusal pressure attained. Changes were subsequently attenuated during each occlusion, depending on the partial restoration of intrasinusal pressure. After barosensory denervation of the carotid sinuses, the cardiovascular responses to bilateral occlusions were reduced, but the respiratory ones were not affected. During 100% O2 breathing in cats with intact innervation or carotid barodenervation, the respiratory responses to bilateral occlusions were much reduced and delayed, or even absent. That the above circulatory and respiratory effects of carotid occlusions were of reflex nature was demonstrated by their elimination after bilateral section of the carotid (sinus) nerves. Results indicate that while barosensory withdrawal during carotid occlusion is mostly responsible for reflex hypertension and bradycardia, chemosensory excitation induced by this maneuver is the major cause of reflex hyperventilation.
Research Interests: Cats, Blood Pressure, Female, Animals, Male, and 5 moreHeart rate, Respiration, Reflex, Carotid Body, and Carotid Arteries
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In spontaneously breathing, pentobarbitone anesthetized cats, we recorded simultaneously the impulses in the chemosensory fibers of both carotid (sinus) nerves, to analyze the correlations between the frequencies of chemosensory... more
In spontaneously breathing, pentobarbitone anesthetized cats, we recorded simultaneously the impulses in the chemosensory fibers of both carotid (sinus) nerves, to analyze the correlations between the frequencies of chemosensory discharges (f chi) and their activation (¿df chi/dt¿a) and deactivation (¿df chi/dt¿d) rates. We studied the chemosensory responses to brief exposures to hypoxia (100% N2; 5-s and 10-s) and hyperoxia (100% O2; 30-s), and intravenous injections of excitatory (NaCN 0.2-100 micrograms/kg) and inhibitory (dopamine hydrochloride 0.02-20 micrograms/kg) chemoreceptor agents. Hypoxia increased f chi, with a high temporal correlation between frequency levels in both nerves. Prolonging hypoxic stimulation increased ¿df chi/dt¿d, with preservation of ¿df chi/dt¿a. Hyperoxic exposure produced highly correlated decreases in f chi in both nerves, but reduced correlation in df chi/dt. Increasing doses of NaCN produced analogous increments in f chi, df chi/dt and their correlations, the ¿df chi/dt¿a/¿df chi/dt¿d ratio remaining constant along all the experimental range, except in one animal in which the ratio increased in both nerves alike. Dopamine reduced f chi bilaterally, with chemosensory silencing being reached with doses of about 0.2-0.5 microgram/kg, the correlations between f chi's of both nerves remaining constant within the range analyzed. Maximal ¿df chi/dt¿d was not affected along the range of dopamine doses, except in one animal in which it increased in both nerves. It is concluded that both carotid nerves convey similar quantitative information to the brain stem. Thus, the carotid nerves constitute either cooperative inputs or redundant afferences contributing to a high safety factor.
Research Interests: Cats, Biological Sciences, Anoxia, Animals, Male, and 5 moreBiological, Carotid Sinus, Time Factors, Carotid Body, and Hyperoxia
PM Gil1, 2, LA Gurovich3, B. Schaffer4, J. Alcayaga5 and R. Iturriaga6 1Instituto de Investigaciones Agropecuarias (INIA), La Cruz, Chile 2Centro Regional de Estudios en Alimentos Saludables, Valparaíso, Chile 3Departamento de... more
PM Gil1, 2, LA Gurovich3, B. Schaffer4, J. Alcayaga5 and R. Iturriaga6 1Instituto de Investigaciones Agropecuarias (INIA), La Cruz, Chile 2Centro Regional de Estudios en Alimentos Saludables, Valparaíso, Chile 3Departamento de Fruticultura y Enología, Facultad de ...
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In spontaneously breathing, pentobarbitone anesthetized cats, we recorded simultaneously the impulses in the chemosensory fibers of both carotid (sinus) nerves, to analyze the correlations between the frequencies of chemosensory... more
In spontaneously breathing, pentobarbitone anesthetized cats, we recorded simultaneously the impulses in the chemosensory fibers of both carotid (sinus) nerves, to analyze the correlations between the frequencies of chemosensory discharges (f chi) and their activation (¿df chi/dt¿a) and deactivation (¿df chi/dt¿d) rates. We studied the chemosensory responses to brief exposures to hypoxia (100% N2; 5-s and 10-s) and hyperoxia (100% O2; 30-s), and intravenous injections of excitatory (NaCN 0.2-100 micrograms/kg) and inhibitory (dopamine hydrochloride 0.02-20 micrograms/kg) chemoreceptor agents. Hypoxia increased f chi, with a high temporal correlation between frequency levels in both nerves. Prolonging hypoxic stimulation increased ¿df chi/dt¿d, with preservation of ¿df chi/dt¿a. Hyperoxic exposure produced highly correlated decreases in f chi in both nerves, but reduced correlation in df chi/dt. Increasing doses of NaCN produced analogous increments in f chi, df chi/dt and their corr...
Research Interests: Cats, Biological Sciences, Anoxia, Animals, Male, and 5 moreBiological, Carotid Sinus, Time Factors, Carotid Body, and Hyperoxia
Using a chronoamperometric technique with carbon-fiber microelectrodes and neural recordings, we simultaneously measured the effects of the following procedures on catecholamine efflux (delta CA) and frequency of chemosensory discharges... more
Using a chronoamperometric technique with carbon-fiber microelectrodes and neural recordings, we simultaneously measured the effects of the following procedures on catecholamine efflux (delta CA) and frequency of chemosensory discharges (fx) from superfused cat carotid body: 1) the addition of CO2-HCO3- to Tyrode solution previously buffered with N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid, maintaining pH at 7.40; 2) hypercapnia (10% CO2, pH 7.10); 3) hypoxia (PO2 h approximately 40 Torr) with and without CO2-HCO3-; and 4) the impact of several boluses of dopamine (DA; 10-100 micrograms) on hypoxic and hypercapnic challenges. With CO2-HCO3-, hypoxia increased fx which preceded delta CA increases, whereas hypercapnia raised fx but did not consistently increase delta CA. Repeated stimuli induced similar fx increases, but attenuated delta CA. After DA, hypoxia produced larger delta CA, which preceded chemosensory responses. Without CO2-HCO3-, hypoxia produced a similar pat...
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The petrosal ganglion contains most of the perikarya of sensory neurons of the glossopharyngeal nerve. We studied the number and size of neuronal somata in 4 petrosal ganglia from adult cats. Ganglia were serially sectioned in length at 8... more
The petrosal ganglion contains most of the perikarya of sensory neurons of the glossopharyngeal nerve. We studied the number and size of neuronal somata in 4 petrosal ganglia from adult cats. Ganglia were serially sectioned in length at 8 microns, sections drawn through a projection microscope, and those neuronal profiles presenting nuclei and nucleoli on each section were counted and their areas measured. The number of neurons ranged from 2311 to 3429 (2908 +/- 271; mean +/- SEM). Neurons were symmetrically distributed around the longitudinal axes of most ganglia, with a skewed distribution in only one ganglion. The sectional area of most neurons (> 98%) ranged between 250 and 1725 microns 2, with median values of 667-963 microns 2. Area distributions were significantly different, but differences never exceeded 8.2% in related area bins. The ganglion presenting a skewed count distribution and the highest median area departed from the rest, with differences surpassing 25%. We con...
Research Interests: Cats, Biological Sciences, Humans, Female, Animals, and 5 moreMale, Biological, Adult, Basal ganglia, and Glossopharyngeal Nerve
The effects of common carotid artery occlusions on the afferent activity recorded from the carotid (sinus) nerve were studied in 20 pentobarbitone anesthetized cats. Ipsilateral occlusions lowered intrasinusal pressure down to 15-100... more
The effects of common carotid artery occlusions on the afferent activity recorded from the carotid (sinus) nerve were studied in 20 pentobarbitone anesthetized cats. Ipsilateral occlusions lowered intrasinusal pressure down to 15-100 torr, depending on previous pressures, and resulted in silencing of carotid barosensory impulses. For cats breathing room air and with mean systemic arterial pressure below 125 torr, chemosensory excitation was induced whenever these occlusions lasted 5 sec or longer and it persisted during 10 min occlusions. The chemosensory excitation had a delay of about 4 sec and the maximal frequency of discharges was attained at nearly 30 sec, followed by a maintained submaximal level of about 80-90% of the peak frequency. For ipsilateral occlusions performed under 100% O2 inhalation, the delay of the excitation was increased to ca. 20 sec and the maximal frequency attained only 30-40% of that obtained for the same animal when breathing room air. Bilateral occlusi...
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The effects evoked by 1 min occlusions of the common carotids were studied in 16 spontaneously breathing pentobarbitone anesthetized cats. Unilateral occlusions induced increases in systemic arterial pressure (to 111.5% of basal), but no... more
The effects evoked by 1 min occlusions of the common carotids were studied in 16 spontaneously breathing pentobarbitone anesthetized cats. Unilateral occlusions induced increases in systemic arterial pressure (to 111.5% of basal), but no changes in ventilation. Bilateral occlusions provoked larger increases in systemic arterial pressure (to 137.5% of basal) and mild tachycardia, associated with pulmonary and alveolar hyperventilation. Breath-by-breath minute volume augmented (to an averaged maximum of 144.7% of basal), the increase in tidal volume being more important than that of respiratory frequency. The maximal changes occurred shortly after occlusion and they were inversely but not linearly related to the minimal levels of intrasinusal pressure attained. Changes were subsequently attenuated during each occlusion, depending on the partial restoration of intrasinusal pressure. After barosensory denervation of the carotid sinuses, the cardiovascular responses to bilateral occlusio...