Browsing by Author "ZAPATA, P"

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    ACUTE CHANGES IN VENTILATION AND BLOOD-PRESSURE INDUCED BY INHALATION OF TOBACCO-SMOKE
    (1976) ZAPATA, P; ZUAZO, A; LLADOS, F
    Inhalation of cigarette smoke through a tracheal cannula was induced in cats anesthetized with pentobarbital. Smoking of tobacco cigarettes produced increased ventilation and systemic hypertension, which were found to be due to their nicotine content. Respiratory stimulation and the increase in diastolic pressure were abolished by acute section of buffer nerves, but the mediation of carotid nerves was more important than that of the vagi for evoking reflex hyperventilation. Tobacco smoking induced a marked increase in the frequency of chemosensory impulses recorded from the carotid nerves, an effect due to its nicotine content.
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    ANTAGONISM OF DOPAMINE-INDUCED CHEMOSENSORY INHIBITION BY ERGOT ALKALOIDS
    (1978) ZAPATA, P; LARRAIN, C
    Intracarotid and i.v. injections of ergometrine, methylergometrine, ergotamine, dihydroergotamine, dihydroergotoxine and 2-Br-.alpha.-ergocryptine depressed the frequency of chemosensory impulses, recorded from the carotid nerve of anesthetized cats. After administration of ergot alkaloids, dopamine-induced inhibition of chemosensory activity was blocked; this effect was not associated with blocking of .alpha.-adrenoceptors for ergometrine, methylergometrine, ergotamine and 2-Br-.alpha.-ergocryptine, but it coincided with .alpha.-adrenergic antagonism for dihydroergotamine and dihydroergotoxine. Ergot alkaloids can act on carotid body chemoreceptors as dopamine analogs and antagonists.
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    BLOCKADE OF DOPAMINE-INDUCED CHEMOSENSORY INHIBITION BY DOMPERIDONE
    (1984) ZAPATA, P; TORREALBA, F
    The sensory discharges from the carotid body chemoreceptors of the cat are transiently inhibited by dopamine (DA) injections. This chemosensory inhibition was effectively blocked by domperidone, a selective antagonist of D2 dopaminoceptors. The basal frequency of spontaneous chemosensory impulses was immediately and sustainly increased after domperidone, suggesting the withdrawal of a tonic inhibition of chemosensory discharges by endogenous DA released from glomus cells. The peripheral dopaminergic modulation of chemoreflexes may be separately blocked by domperidone, a drug unable to cross the blood-brain barrier.
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    CARDIOVASCULAR-RESPONSES TO HYPOXIA IN THE SPONTANEOUSLY BREATHING CAT - REFLEXES ORIGINATING FROM CAROTID AND AORTIC BODIES
    (1983) SERANI, A; LAVADOS, M; ZAPATA, P
    The heart rate (fH) and systemic arterial pressure (Pa) responses to transient anoxemic and cytotoxic hypoxia were studied in 18 pentobarbitone-anesthetized, spontaneously breathing cats, by applying N2 tests and i.v. injections of NaCN. Hyperventilation was accompanied by short-latency increases in Pa and fH; they persisted after bilateral vagotomy, sparing the aortic nerves. Acute section of carotid or aortic nerves in different sequences reduced both fH and Pa responses, the contribution of both pairs of nerves being similar. The recording of carotid chemosensory discharges showed transient stimulus-dependent increases in their frequency, to which the ensuing fH and Pa rises were correlated. After sectioning the 4 buffer nerves, hypoxia provoked long-lasting hypotension and bradycardia. Tachycardia was also observed in response to hypoxia in 4 out of 6 chloralose-anesthetized spontaneously breathing cats, the other 2 presenting bradycardia. The direction of these cyanide-induced changes in fH was not modified by bilateral vagotomy. Tachycardia and hypertension in response to hypoxia are not vagally-mediated consequences of hyperventilation.
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    CAROTID-BODY CHEMORECEPTOR EXCITATION PRODUCED BY CAROTID OCCLUSION
    (1986) ALCAYAGA, J; ITURRIAGA, R; ZAPATA, P
    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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    COMPARISON OF THE SUBCELLULAR-DISTRIBUTION OF ALVEOLAR SURFACTANT IN 2 MAMMALIAN-SPECIES OF SIMILAR BODY-WEIGHT - CAT AND RABBIT
    (1992) OYARZUN, MJ; MORGADO, E; DUSSAUBAT, N; LATHROP, ME; ITURRIAGA, R; LARRAIN, C; ZAPATA, P
    1. We studied the total amount and subcellular distribution of alveolar surfactant, extracted through bronchoalveolar lavage of anesthetized cats and rabbits. This was correlated to several morphometric and ventilatory variables of these animals.
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    CONFREG - A BASIC PROGRAM FOR CALCULATING AND PLOTTING CONFIDENCE-REGIONS BASED ON CORRELATIONAL ANALYSES
    (1989) ITURRIAGA, R; ALCAYAGA, J; ZAPATA, P
    Many observations encountered in biological and medical research are randomly distributed in bivariate scales, and thus not susceptible to simple regression analyses. Since such data are depicted by ellipses in scatter diagrams, a computer program to calculate the confidence regions for the means or the total data of bivariate samples was written in BASIC for correlational analyses. The program, based on the principal axes algorithm, plots the calculated confidence regions as an elliptic area, using the fitted equations for its major and minor axes. The program displays the sample parameters required to perform comparisons between different groups of experimental conditions.
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    CORRELATIVE CONTRIBUTION OF CAROTID AND AORTIC AFFERENCES TO THE VENTILATORY CHEMOSENSORY DRIVE IN STEADY-STATE NORMOXIA AND TO THE VENTILATORY CHEMOREFLEXES INDUCED BY TRANSIENT HYPOXIA
    (1989) EUGENIN, J; LARRAIN, C; ZAPATA, P
    The contributions of the peripheral arterial chemoreceptors to the tonic and phasic reflex ventilatory regulation were studied in spontaneously breathing pentobarbitone anesthetized adult cats. The chemosensory drive during eucapnic normoxia was inferred from the transient ventilatory effects induced by anesthetic blockade of the buffer nerves. Aortic nerves block did not modify ventilation. Carotid nerves block provoked transient ventilatory depression, decreasing VT by 46% and fR by 26%, followed by recovery to steady-state values in VT, fR and PETCO2. Changes in PETCO2 were correlated with those in VT, but not with those in fR. The ventilatory effects of blocking a given carotid nerve were more intense when the contralateral carotid nerve was already blocked. This effect may be an expression of hypoadditive interactions between carotid nerves inputs with respect to chemosensory drive of ventilation. Analysis of the dose-response curves for the ventilatory reflexes evoked by NaCN i.v., before and after blockade of the buffer nerves, revealed major contributions of the carotid nerves, with small contributions of the aortic nerves to the responses to high doses of NaCN. The contributions of each carotid nerve to the tonic chemosensory drive and to the phasic ventilatory chemoreflexes were highly correlated (rs = 0.90; p < 0.01). We propose that a family of modulatory functions may describe the effects exerted by the peripheral arterial chemoreceptors upon the tonic ventilatory drive in normoxia and the phasic reflex responses evoked by hypoxia. While the carotid nerves mediated modulation is evident in normoxia, that provided by both aortic nerves is only expressed during pronounced hypoxia.
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    DOPAMINE-BETA-HYDROXYLASE ACTIVITY IN NORMAL AND SYMPATHECTOMIZED CAROTID-BODIES
    (1976) MORGADO, E; LLADOS, F; ZAPATA, P
    Normal carotid bodies excised from cats showed DBH [dopamine-.beta.-hydroxylase] values of 5.04 .+-. 0.53 nmol [3H]octopamine formed/h per 100 mg tissue (.hivin.x .+-. S.E.). Values from sympathectomized carotid bodies were not significantly different. While the ganglio-glomerular nerves, providing the sympathetic innervation of the carotid bifurcation, had a high DBH level, this was low in the carotid sinus nerve, providing its sensory innervation. Glomeral DBH may be contained in a special type of noradrenergic glomus cells, distinct from the most common dopaminergic glomus cells.
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    DOPAMINE-INDUCED VENTILATORY DEPRESSION IN THE RAT, MEDIATED BY CAROTID NERVE AFFERENTS
    (1981) CARDENAS, H; ZAPATA, P
    In pentobarbitone-anesthetized rats, i.v. injections of dopamine (DA) at 10-8-10-5 g/kg led to transient ventilatory depression, usually not associated with changes in systemic arterial pressure. DA-induced ventilatory depression consisted of decreases in tidal volume and respiratory frequency in 12 rats and in bradypnea without changes in tidal volume in 5 rats. After bilateral section of the carotid nerves, ventilatory responses to DA were abolished or greatly diminished. DA evidently inhibits carotid body chemosensory discharges in the rat. Chemosensory activity may directly affect respiratory frequency.
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    DUAL EFFECTS OF DOPAMINE UPON CHEMOSENSORY RESPONSES TO CYANIDE
    (1980) CARDENAS, H; ZAPATA, P
    Changes in chemosensory responses to i.v. NaCN during i.v. infusions of dopamine (DA) were studied in pentobarbitone-anesthetized cats. After sectioning both carotid nerves, 1 of them was prepared for electrophysiological recordings of its chemosensory impulses. Basal chemosensory activity was maintained at a reduced level during DA infusions at a rate of 10 .mu.g/kg per min. While sensitivity to NaCN was not modified, reactivity to this agent was reduced for low doses, but enhanced for high doses. Chemoreceptor responses to histotoxic hypoxia are evidently rectified by DA. This is discussed in terms of a modulatory role of endogenous DA in the generation of carotid body sensory impulses.
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    EFFECTS OF 6-HYDROXY-DOPAMINE ON CAROTID-BODY CHEMO-SENSORY ACTIVITY
    (1978) ZUAZO, A; ZAPATA, P
    6-OH-DA [6-hydroxy-dopamine] HBr (5-25 mg) injected into 1 common carotid artery of pentobarbitone-anesthetized cats, induced a transient inhibition of chemosensory discharges recorded from the ipsilateral carotid nerve, but did not change chemosensory frequency during spontaneous ventilation, periodic deep breaths and asphyxia. Chemosensory activities recorded simultaneously from both carotid nerves showed no differences in their inhibitory responses to dopamine and their excitatory responses to NaCN, up to 48 h after the injections of 6-OH-DA. Apparently 6-OH-DA acts initially as a dopamine analog, and does not impair subsequent carotid body chemoreception or dopamine-induced inhibition, as doses producing abolition of noradrenergic transmission.
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    EFFECTS OF BODY-TEMPERATURE ON CHEMOSENSORY ACTIVITY OF THE CAT CAROTID-BODY INSITU
    (1991) LOYOLA, H; FADIC, R; CARDENAS, H; LARRAIN, C; ZAPATA, P
    The effects of changes in body core temperature (T(B)) upon the frequency of chemosensory discharges (f(x)) from one carotid nerve were studied in pentobarbitone anesthetized cats. Raising T(B) from 35 to 40-degrees-C increased f(x) in some cats, an effect more commonly seen after contralateral carotid neurotomy. In other animals, the simultaneously increased alveolar ventilation counteracted the above effect. A multiple correlation analysis of global data showed predicted increases in f(x) in response to raising T(B) at different CO2 levels.
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    FLOW-DEPENDENT CHEMOSENSORY ACTIVITY IN THE CAROTID-BODY SUPERFUSED INVITRO
    (1988) ALCAYAGA, J; ITURRIAGA, R; ZAPATA, P
    The relationship between carotid body chemoreceptor activity and flow was studied in preparations superfused in vitro. The carotid bodies were excised from pentobarbitone-anesthetized cats and superfused with modified Tyrode''s solution, buffered with HEPES-NaOH to pH 7.41. The bath temperature was kept constant at 37.7.degree. C. The frequency of chemosensory discharges from the entire carotid nerve was determined during steady-state superfusion with 100% or 20% O2-equilibrated saline at flow rates between 0.15 and 2.95 ml/min, and during 5 min flow interruptions. The peak frequency evoked by flow interruptions was maximal and independent of previous superfusion flows, but the half-excitation time of chemosensory responses to flow interruption was minimal when preceded by superfusion with 100% O2-equilibrated saline at 0.7 ml/min. In steady-state conditions, mean chemosensory activity was higher at lower rates of flow, and, at constant flow, higher under 20% O2 than under 100% O2. To allow comparisons of all data, basal frequencies at given basal flows were referred to their own maximal frequencies evoked by flow interruptions. The best fitting for the relation between basal chemosensory activity and superfusion flow was provided by inverse sigmoid (logistic decay) curves: r = -0.90 and -0.84, at 100% and 20% O2 levels, respectively. The maximal gains were at about 0.78 and 0.86 ml/min, respectively. It is concluded that the chemosensory discharge frequency recorded from carotid bodies superfused in vitro is determined by the superfusion flow, when all other natural chemoreceptor stimuli are held constant.
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    INHIBITION IN CAROTID-BODY CHEMORECEPTORS MEDIATED BY D-2 DOPAMINOCEPTORS - ANTAGONISM BY BENZAMIDES
    (1983) ZAPATA, P; SERANI, A; LAVADOS, M
    Inhibition of chemosensory nerve impulses in the cat is evoked by dopamine (DA) applied to carotid body chemoreceptors. Pharmacological characterization of the dopaminoceptors involved in this action was determined through their blockade with benzamides, selective antagonists of D-2 receptors. Both metoclopramide and sulpiride were effective blockers of DA-induced chemosensory inhibition. Both drugs induced an immmediate increase in the frequency of carotid nerve chemosensory impulses, suggesting the presence of previous tonic inhibition of chemoreceptor discharges by endogenous DA release from glomus cells.
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    REGIONAL SYMPATHECTOMY INDUCED BY INTRA-ARTERIAL 6-HYDROXY-DOPAMINE
    (1978) ZUAZO, A; ZAPATA, P
    Single intra-carotid injections of 5-15 mg of 6-OHDA [6-hydroxydopamine] HBr in adult cats reduced or abolished the responses of the ipsilateral nictitating membrane to electrical stimulation of post-ganglionic sympathetic nerves and intra-carotid injections of tyramine; the responses of the contralateral nictitating membrane to the same stimuli remained normal. One to five days after 6-OHDA, the ipsilateral nictitating membranes, unresponsive to sympathetic stimulation, were hypersensitive to i.v. injections of adrenaline [epinephrine] or noradrenaline [norepinephrine]. The advantages of regional over systemic chemical sympathectomy are discussed.
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    RELATIVE CONTRIBUTION OF CAROTID AND AORTIC BODIES TO CYANIDE-INDUCED VENTILATORY RESPONSES IN THE CAT
    (1981) SERANI, A; ZAPATA, P
    The participation of afferences from carotid and aortic bodies to the hyperventilation caused by cytotoxic hypoxia was assessed in pentobarbitone-anesthetized cats. Dose-response curves for the ventilatory effects induced by i.v. injections of NaCN were obtained before and after successive denervations of peripheral chemoreceptors, in different sequences. Bilateral aortic neurotomy (BAN) or unilateral carotid neurotomy (UCN) did not affect significantly the minimal sensitivity to the drug, although maximal reactivity was reduced in some cats. After bilateral carotid neurotomy (BCN), with preservation of aortic nerves, sensitivity was reduced, but hyperventilation was still provoked by large doses of CN. BAN + BCN abolished the ventilatory responses to the drug. In cats with BAN + UCN, ventilatory responses had a high degree of correlation with increases of carotid chemosensory discharges in the range between 200% of control and the gasping threshold. The aortic bodies of the cat play a significant role in the hyperventilation produced by cytotoxic hypoxia, although it is less marked than that induced through the carotid bodies.