Coherence of chemosensory discharges in cats' carotid nerves. Cooperative inputs or redundant afferences?
Explore the source record for details and available documents.
Action Potentials↗
Biomedical subjects
P Zapata
Publications and source records attributed to P Zapata.
Effects of dopaminergic blockade upon carotid chemosensory activity and its hypoxia-induced excitation.
The effects of domperidone, antagonist of D2 receptors, on arterial chemoreceptor activity were studied in spontaneously breathing and pentobarbitone anesthetized cats, in which recordings of chemosensory impulse activity were obtained simultaneously from both cut carotid (sinus) nerves. Intravenous injections of domperidone 50 micrograms/kg produced a maintained increase in the basal frequency of chemosensory discharges, after which hyperoxic tests (breathing 100% O2 for 30 s) evoked larger falls in the rate of chemosensory impulses. Chemosensory responses evoked by hypoxic hypoxia (100% N2 tests) and by cytotoxic hypoxia (i.v. injections of NaCN) reached higher impulse rates after domperidone treatment. The effects of domperidone reveal that a resting release of dopamine from glomus cells maintains a low level of basal chemosensory activity under normoxic conditions. Domperidone turns off such restraining dopaminergic control and enhances the transient chemosensory responses to hypoxic stimuli. Present data support a modulatory role for dopamine within the chemoreceptor process, but not its participation as excitatory transmitter between glomus cells and sensory nerve endings.
Animals↗
Effects of expiratory duration on chemoreceptor oscillations.
Explore the source record for details and available documents.
Animals↗
The carotid bodies as thermosensors: experiments in vitro and in situ, and importance for ventilatory regulation.
Explore the source record for details and available documents.
Animals↗
Phrenic nerve activity during artificial ventilation at different body temperatures and its relationships with carotid chemosensory activity.
While the chemoreceptor discharges of carotid bodies in vitro are highly dependent on temperature, these chemoreceptors in situ contribute only moderately to the ventilatory adjustment to changing body temperature (Tb), probably because of the concomitant and reverse changes in natural chemoreceptor stimuli in closed-loop preparations. Accordingly, we studied the frequency of carotid chemosensory discharge (fx) and the phrenic integrated electroneurogram (IENGph) in pentobarbitone anesthetized cats, paralyzed with alcuronium and artificially ventilated, at three steady-state levels of Tb (35.5, 37.5 and 40.2 degrees C), modifying the frequency and volume of the ventilator to maintain PETCO2 within normal range. While fx increases along with Tb when PETCO2 is allowed to fluctuate freely, its mean basal value was not consistently different at the three Tb's studied under controlled conditions. The amplitude of IENGph was reduced and the frequency of phrenic inspiratory cycles was increased as Tb was raised from 35.5 to 37.5 degrees C and then to 40.2 degrees C. Brief 100% O2 inhalations and i.v. injections of dopamine produced minimal depressions of IENGph amplitude in hypothermia, but pronounced although similar depressions in normothermia and hyperthermia. i.v. injections of NaCN augmented fx and IENGph in dose related manner, and the relationships between both variables showed larger changes in IENGph at the hypothermic and normothermic conditions when expressed in absolute terms, but not when expressed in relative terms. Thus, the chemosensory input is not consistently modified by thermal levels under controlled ventilatory conditions, but the chemosensory drive of the ventilatory output is less pronounced in hypothermia. The chemosensory input is similarly affected by varying degrees of cytotoxic hypoxia at different Tb's, but the ventilatory output is less vigorously increased in hyperthermia, pointing to a decreased reflex gain in that condition.
Animals↗
A report on the evolution of this journal and an analysis of its present state and perspectives.
This journal appeared as Archivos de Biología y Medicina Experimentales between 1964 and 1992, its name being changed into Biological Research in 1992. This is a report on the past and present of the journal, analyzing the problems of a scientific journal published in English but produced in Latin America, those that its contributors must deal with in the preparation of the manuscripts, those involved in the evaluation procedures and editing of material for the press, and those about coverage by indexing services and the international recognition of the journal quality.
Chile↗
Thermal dependence of chemosensory activity in the carotid body superfused in vitro.
We studied the relationship between chemosensory activity and temperature in carotid bodies excised from pentobarbitone-anesthetized cats, and superfused in vitro at flows between 0.4 and 2.0 ml/min with modified Tyrode's solution buffered with HEPES at pH 7.43. The basal frequencies of chemosensory discharges were recorded from the entire carotid nerve at different steady thermal conditions. For preparations superfused with saline equilibrated with 100% O2, thermally dependent increases in frequency were observed, with significant differences between all nearby thermal stages separated by 0.5 degrees C steps between 36.0 and 38.5 degrees C. The larger gains were recorded between higher temperatures at high flows, between mid temperatures at intermediate flows, and between lower temperatures at low flows. The critical temperature for the calculated maximal gain was directly correlated to superfusion flow. The basal frequencies were consistently elevated when switching to saline equilibrated with 20% O2 and no significant differences in mean ranks were recorded between 36 and 37 degrees C, as between 38 and 39 degrees C, but frequencies at 36-37 degrees C were significantly higher than those at 38-39 degrees C. Brief rises in chemosensory discharges were evoked by injections of NaCN applied to carotid bodies superfused with saline equilibrated with 100% O2. The least effective dose was lower at 40 degrees C than at 37.5 degrees or 35.0 degrees C, but the reactivity and slope were not significantly different. It is concluded that the carotid body chemoreceptors fulfill the criteria for being considered as thermosensors, and that their frequency of discharges is thermally modulated within a range close to physiological body temperature.
Animals↗
Thermal effects upon the chemosensory drive of ventilation.
Explore the source record for details and available documents.
Animals↗
Comparison of the subcellular distribution of alveolar surfactant in two mammalian species of similar body weight: cat and rabbit.
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. 2. Lung weight was significantly larger in the cat while respiratory frequency and minute ventilation were significantly larger in the rabbit. No significant differences were observed in tidal volume, total lung capacity, P(a)O2, P(a)CO2 and pH(a). 3. While both species had similar protein contents in the bronchoalveolar lavage, rabbits had larger phospholipid contents, mostly distributed in the lighter, more active subfractions. 4. With regard to the estimated values obtained from allometric equations derived for mammals, the rabbit presented a lung weight of nearly one-third of the estimated one, an exceedingly larger minute ventilation (by nearly 60%) and a respiratory frequency twice the calculated one. 5. We suggest that the different distribution of alveolar surfactant in these species may be explained by disparities in their ventilatory demands, the rabbit having a higher respiratory frequency and a larger minute ventilation, performed by a mass of lung tissue lower than that corresponding to its body mass.
Animals↗
Effects of body temperature on chemosensory activity of the cat carotid body in situ.
The effects of changes in body core temperature (TB) upon the frequency of chemosensory discharges (fx) from one carotid nerve were studied in pentobarbitone anesthetized cats. Raising TB from 35 to 40 degrees C increased fx 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 fx in response to raising TB at different CO2 levels.
Analysis of Variance↗
Thermal effects on ventilation in cats: participation of carotid body chemoreceptors.
In pentobarbitone anesthetized cats, raising body temperature from 37 to 40 degrees C by external heat increased respiratory frequency, tidal volume, frequency of spontaneous gasps and mean inspiratory flow. It reduced end-tidal CO2 pressure, together with inspiratory and expiratory durations. After bilateral section of the carotid nerves, raising body temperature still induced hyperventilation, but the increase in gasp frequency was less pronounced and no significant change in tidal volume was observed. In comparison to steady ventilatory values in the intact condition, significant reductions in tidal volume at 38 degrees C and in gasp frequency at 37, 39 and 40 degrees C were observed after bilateral carotid neurotomy. Brief hyperoxic tests induced transient decreases in tidal volume and increases in end-tidal CO2 pressure which were significantly larger at 40 degrees C than at 37 degrees C. These changes disappeared after bilateral carotid neurotomy. Anesthetic block of both carotid nerves produced transient reductions in tidal volume at any given temperature. We conclude that carotid body afferents contribute to the hyperventilation evoked by hyperthermia. After their interruption, such contribution is replaceable from other thermal afferents.
Animals↗
Factors affecting distribution of alveolar surfactant during resting ventilation.
Few studies have been done to establish the ventilatory factors affecting alveolar surfactant under resting conditions. Experiments in which ventilatory variables were recorded for 4 h were performed in 12 adult cats breathing spontaneously under pentobarbital sodium anesthesia. After the animals were killed and bronchoalveolar lavages (BALs) were performed, the resulting fluid was subjected to differential centrifugation and determinations of proteins, phospholipids (PL), and disaturated phosphatidylcholine (DSPC). Pellet P1+2 was obtained by two centrifugations at 140 g; the supernatant was centrifuged at 1,000 g to obtain pellet P3 and subsequently at 60,000 g to obtain P4. Pellets P3 and P4 had the higher contents of PL and DSPC. Bivariate and multivariate correlational analyses indicate that 1) total PL in BAL was not related to any of the ventilatory variables studied, 2) PL in P3 and P4 fractions was directly correlated to the physiological range of variations in the frequency of large spontaneous gasps (fL), and 3) PL in P1+2 fraction was inversely related to fL. Cats subjected to bilateral section of carotid nerves, although presenting reduced chemosensory drive and ventilatory chemoreflexes, did not exhibit significant differences in resting ventilatory variables nor in alveolar surfactant components. Present results indicate that the total content of alveolar surfactant is not modified by ventilatory variations within physiological range but that the spontaneous occurrence of large gasps increases the proportion of more active forms of alveolar surfactant. This may mediate the role of augmented breaths in keeping lung compliance and preventing atelectasis under resting ventilatory conditions.
Animals↗
Functional recovery of the ventilatory chemoreflexes after partial chronic denervation of the nucleus tractus solitarius.
In pentobarbitone-anesthetized cats breathing spontaneously, we studied whether excision of one petrosal ganglion would modify the reflex efficacy of the remaining carotid and aortic chemoafferences in ventilatory control. Resting ventilation was not affected shortly after the ganglionectomy, but decreased sensitivities and reactivities for changes in tidal volume and respiratory frequency were revealed by dose-response curves for ventilatory chemoreflexes evoked by NaCN i.v. After 2 weeks of ganglionectomy, basal tidal volume was increased, being slightly reduced by contralateral carotid neurotomy, but persisting above control after section of all buffer nerves. The ventilatory chemosensory drive--tested by breathing 100% O2--was unmodified with respect to the acute condition, but the tonic ventilatory influence exerted by the right carotid nerve was diminished. Dose-response curves for reflex changes in tidal volume exhibited increased sensitivity, while those for changes in respiratory frequency showed increased reactivity. Thus, partial chemosensory denervation of the nucleus tractus solitarius triggers a slowly developing increase in the reflex efficacy of the remaining chemosensory inputs. The recovery of sensitivity for reflex changes in tidal volume required the presence of contralateral carotid afferents, while the increased reactivity in respiratory frequency needed the integrity of aortic afferents. The results also suggest an enhanced contribution of central structures other than chemosensory inputs in respiratory control after partial deafferentation.
Animals↗
Disappearance of opioidergic tone on LH secretion in underfed prepubertal sheep.
A study was conducted to determine whether an opioid tonus inhibitory of LH secretion is present in underfed prepubertal sheep. Ten Suffolk ewe lambs were subjected to food restriction during 60 days. During this period they were allowed to pasture only 2 hours per day while control ewe lambs were allowed for 10 hours. Body weight and plasma blood levels of glucose, urea and total proteins were measured weekly. At the end of this period, an intravenous injection of Naloxone (NAL, 1.5 mg/kg BW) was given to control and underfed animals followed 60 min later by an intravenous injection of LHRH to test the pituitary responsiveness. Underfed animals did not show an increase in plasma LH while control animals presented a rise from 0.28 +/- 0.08 to 2.02 +/- 0.6 ng/ml after the NAL stimulus (P less than 0.05). The response to LHRH was similar in both group of animals. Basal plasma levels of insulin were lower in underfed ewe lambs than in control animals (P less than 0.05). Underfed animals were placed on plain feeding with a schedule similar to control lambs for 30 days and the same experiment was repeated. During this occasion, NAL increased plasma LH concentration in both group of lambs. Levels of plasma insulin were not different in both groups. The lack of effect of NAL on LH secretion in food restricted ewe lambs suggests that the opioid modulation of LH secretion is absent by underfeeding in female prepubertal sheep.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
CONFREG: a BASIC program for calculating and plotting confidence regions based on correlational analyses.
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.
Animals↗
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.
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 those 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 less than 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.
Afferent Pathways↗
Flow-dependent chemosensory activity in the carotid body superfused in vitro.
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 degrees 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.
Animals↗
Reflex effects evoked by stimulation of hypoglossal afferent fibers.
In pentobarbitone-anesthetized cats, electrical stimulation of the central ends of the main trunks of transected hypoglossal nerves evoked vascular (pressor or depressor) reactions, mydriasis, slow and deep breathing, and reflex activation of laryngeal and facial muscles. Stimulation of the central end of the transected ramus descendens hypoglossi also provoked reflex contraction of cricothyroideus. These reflexes may be elicited also after intracranial section of hypoglossal nerve roots, but not after intracranial section of ipsilateral vagal roots. The above reflexes were abolished by acute section of the ipsilateral hypoglossonodosal branch, but they may be reproduced by electrical stimulation of the central end of this anastomotic branch between hypoglossal nerve and nodose ganglion. Stimulation of the central end of one transected hypoglossus evoked reflex efferent discharges in contralateral hypoglossus and contraction of contralateral tongue muscles. Stimulation of the central end of one transected hypoglossal end-branch inhibited efferent discharges in another end-branch. The crossed hypoglossohypoglossal reflex and the ipsilateral reflex inhibition were abolished by section of the hypoglossonodosal branch or vagal roots at the stimulated side. We conclude that reflexes evoked by stimulation of peripheral hypoglossal nerve in cats are mediated by afferent fibers directed to the nodose ganglion and entering the brain stem via vagal roots.
Afferent Pathways↗