Two discharge patterns of carotid body chemoreceptors in the goat

1990 ◽  
Vol 69 (2) ◽  
pp. 734-739 ◽  
Author(s):  
W. Z. Niu ◽  
M. J. Engwall ◽  
G. E. Bisgard
Keyword(s):  
Carotid Body ◽  
Interspike Interval ◽  
Spike Trains ◽  
Discharge Pattern ◽  
The Difference ◽  
Discharge Patterns ◽  
Carotid Body Chemoreceptors ◽  
Arterial Po2 ◽  
Interval Distribution ◽  
Prominent Peak

Twenty-nine single carotid body chemoreceptor units recorded during normocapnic normoxia from 20 anesthetized goats were classified into two groups by discharge pattern. Thirteen fibers, which had interspike interval distributions with a prominent peak [24.0 +/- 9.8% (SD)] at 0- to 20-ms bin, were termed bursting fibers (BF). The 16 remaining fibers were termed nonbursting fibers (NBF); these had no notable peak in the interval distributions. During hypoxia and hypercapnia, the chemoreceptor fibers continued to discharge in their established patterns. The interval distribution of most NBF spike trains could be described with the Poisson process, but none of the BF could be. However, except for the intervals in the range of 0-20 ms, the interval distribution of the BF could be described as exponential. This study suggests that 1) there are two distinct populations of the goat chemoreceptor fiber, each with an inherent discharge pattern; 2) the chemoreceptor did not code information about arterial PO2 and PCO2 in different patterns; and 3) the basic chemotransduction mechanism is likely the same in BF and NBF, and the difference in discharge pattern is more likely to reflect processes downstream from the transducer.

Improvements to the Sensitivity of Gravitational Clustering for Multiple Neuron Recordings

2000 ◽  
Vol 12 (11) ◽  
pp. 2597-2620 ◽  
Author(s):  
Stuart N. Baker ◽  
George L. Gerstein
Keyword(s):  
Interspike Interval ◽  
Simulation Method ◽  
Spike Trains ◽  
The Novel ◽  
Limited Data ◽  
Neuronal Synchrony ◽  
Gravitational Clustering ◽  
Using Data ◽  
Interspike Interval Distribution ◽  
Interval Distribution

We outline two improvements to the technique of gravitational clustering for detection of neuronal synchrony, which are capable of improving the method's detection of weak synchrony with limited data. The advantages of the enhancements are illustrated using data with known levels of synchrony and different interspike interval distributions. The novel simulation method described can easily generate such test data. An important dependence of the sensitivity of gravitational clustering to the interspike interval distribution of the analysed spike trains is described.

The essential role of carotid body chemoreceptors in sleep apnea

2003 ◽  
Vol 81 (8) ◽  
pp. 774-779 ◽  
Author(s):  
Curtis A Smith ◽  
Hideaki Nakayama ◽  
Jerome A Dempsey
Keyword(s):  
Sleep Apnea ◽  
Carotid Body ◽  
Respiratory Acidosis ◽  
Periodic Breathing ◽  
Peripheral Chemoreceptors ◽  
Carotid Chemoreceptors ◽  
Ventilatory Responses ◽  
Carotid Bodies ◽  
The Difference ◽  
Carotid Body Chemoreceptors

Sleep apnea is attributable, in part, to an unstable ventilatory control system and specifically to a narrowed "CO2 reserve" (i.e., the difference in PaCO2 between eupnea and the apneic threshold). Findings from sleeping animal preparations with denervated carotid chemoreceptors or vascularly isolated, perfused carotid chemoreceptors demonstrate the critical importance of peripheral chemoreceptors to the ventilatory responses to dynamic changes in PaCO2. Specifically, (i) carotid body denervation prevented the apnea and periodic breathing that normally follow transient ventilatory overshoots; (ii) the CO2 reserve for peripheral chemoreceptors was about one half that for brain chemoreceptors; and (iii) hypocapnia isolated to the carotid chemoreceptors caused hypoventilation that persisted over time despite a concomitant, progressive brain respiratory acidosis. Observations in both humans and animals are cited to demonstrate the marked plasticity of the CO2 reserve and, therefore, the propensity for apneas and periodic breathing, in response to changing background ventilatory stimuli.Key words: sleep apnea, carotid bodies, hypocapnia, apneic threshold, periodic breathing.

Peripheral chemoreceptors in respiratory oscillations

1985 ◽  
Vol 58 (6) ◽  
pp. 1901-1908 ◽  
Author(s):  
S. Lahiri ◽  
C. Hsiao ◽  
R. Zhang ◽  
A. Mokashi ◽  
T. Nishino
Keyword(s):  
Carotid Body ◽  
Venous Return ◽  
Critical Role ◽  
Blood Gases ◽  
Experimental Conditions ◽  
Cardiorespiratory Control ◽  
Arterial Blood ◽  
Carotid Body Chemoreceptors ◽  
Peripheral Chemoreflex ◽  
Arterial Po2

The hypothesis that instability of cardiorespiratory control may depend on the response and sensitivity of carotid body chemoreceptors to arterial blood gases was studied in anesthetized cats under three different experimental conditions. 1) Following administration of the peripheral dopamine receptor blocker [domperidone (0.6–0.8 mg X kg-1, iv)], carotid chemoreceptor activity and its sensitivity to CO2 during hypoxia increased, leading to cardiorespiratory oscillations at low arterial PO2 in four of eight cats. Inhalation of 100% O2 promptly decreased chemoreceptor activity and eliminated the oscillations. Inhalation of CO2 stimulated the chemoreceptor activity and ventilation but did not eliminate the oscillations. Bilateral section of carotid sinus nerves abolished the cardiorespiratory oscillations. The implication is that the dopaminergic system in the carotid body keeps chemoreceptor responses to blood gas stimuli suppressed and hence cardiorespiratory oscillations damped. 2) Hypotension and circulatory delay induced by the partial occlusion of venous return led to cardiorespiratory oscillations at low but not at high arterial PO2. 3) A few cats developed cardiorespiratory oscillations without any particular experimental intervention. These oscillations were independent of arterial PO2 and chemoreceptor activity. Thus it is reasonable to conclude that the peripheral chemoreflex can play a critical role in developing cardiorespiratory oscillations in certain instances.

scholarly journals Responses of Inferior Colliculus Neurons to Double Harmonic Tones

2007 ◽  
Vol 98 (6) ◽  
pp. 3171-3184 ◽  
Author(s):  
Donal G. Sinex ◽  
Hongzhe Li
Keyword(s):  
Inferior Colliculus ◽  
Auditory System ◽  
Temporal Pattern ◽  
Second Harmonic ◽  
Neural Mechanisms ◽  
Acoustic Properties ◽  
Discharge Pattern ◽  
The Difference ◽  
Discharge Patterns ◽  
Simultaneous Sounds

The auditory system can segregate sounds that overlap in time and frequency, if the sounds differ in acoustic properties such as fundamental frequency (f0). However, the neural mechanisms that underlie this ability are poorly understood. Responses of neurons in the inferior colliculus (IC) of the anesthetized chinchilla were measured. The stimuli were harmonic tones, presented alone (single harmonic tones) and in the presence of a second harmonic tone with a different f0 (double harmonic tones). Responses to single harmonic tones exhibited no stimulus-related temporal pattern, or in some cases, a simple envelope modulated at f0. Responses to double harmonic tones exhibited complex slowly modulated discharge patterns. The discharge pattern varied with the difference in f0 and with characteristic frequency. The discharge pattern also varied with the relative levels of the two tones; complex temporal patterns were observed when levels were equal, but as the level difference increased, the discharge pattern reverted to that associated with single harmonic tones. The results indicated that IC neurons convey information about simultaneous sounds in their temporal discharge patterns and that the patterns are produced by interactions between adjacent components in the spectrum. The representation is “low-resolution,” in that it does not convey information about single resolved components from either individual sound.

Carotid chemoreceptor activity during acute and sustained hypoxia in goats

1988 ◽  
Vol 65 (4) ◽  
pp. 1796-1802 ◽  
Author(s):  
A. M. Nielsen ◽  
G. E. Bisgard ◽  
E. H. Vidruk
Keyword(s):  
Carotid Body ◽  
Discharge Frequency ◽  
Hypoxic Exposure ◽  
Arterial Pco2 ◽  
Afferent Discharge ◽  
Carotid Body Chemoreceptors ◽  
Arterial Po2 ◽  
Sustained Hypoxia ◽  
Related Increase

The role of carotid body chemoreceptors in ventilatory acclimatization to hypoxia, i.e., the progressive, time-dependent increase in ventilation during the first several hours or days of hypoxic exposure, is not well understood. The purpose of this investigation was to characterize the effects of acute and prolonged (up to 4 h) hypoxia on carotid body chemoreceptor discharge frequency in anesthetized goats. The goat was chosen for study because of its well-documented and rapid acclimatization to hypoxia. The response of the goat carotid body to acute progressive isocapnic hypoxia was similar to other species, i.e., a hyperbolic increase in discharge as arterial PO2 (PaO2) decreased. The response of 35 single chemoreceptor fibers to an isocapnic [arterial PCO2 (PaCO2) 38-40 Torr)] decrease in PaO2 of from 100 +/- 1.7 to 40.7 +/- 0.5 (SE) Torr was an increase in mean discharge frequency from 1.7 +/- 0.2 to 5.8 +/- 0.4 impulses. During sustained isocapnic steady-state hypoxia (PaO2 39.8 +/- 0.5 Torr, PaCO2, 38.4 +/- 0.4 Torr) chemoreceptor afferent discharge frequency remained constant for the first hour of hypoxic exposure. Thereafter, single-fiber chemoreceptor afferents exhibited a progressive, time-related increase in discharge (1.3 +/- 0.2 impulses.s-1.h-1, P less than 0.01) during sustained hypoxia of up to 4-h duration. These data suggest that increased carotid chemoreceptor activity contributes to ventilatory acclimatization to hypoxia.

Carotid body excision significantly changes ventilatory control in awake rats

1988 ◽  
Vol 64 (2) ◽  
pp. 666-671 ◽  
Author(s):  
E. B. Olson ◽  
E. H. Vidruk ◽  
J. A. Dempsey
Keyword(s):  
Carotid Body ◽  
Chronic Hypoxia ◽  
Acute Hypoxia ◽  
Respiratory Acidosis ◽  
Co2 Production ◽  
Sham Operation ◽  
Ventilatory Responses ◽  
Carotid Body Chemoreceptors ◽  
Arterial Po2 ◽  
Intact Rats

We determined the effects of carotid body excision (CBX) on eupneic ventilation and the ventilatory responses to acute hypoxia, hyperoxia, and chronic hypoxia in unanesthetized rats. Arterial PCO2 (PaCO2) and calculated minute alveolar ventilation to minute metabolic CO2 production (VA/VCO2) ratio were used to determine the ventilatory responses. The effects of CBX and sham operation were compared with intact controls (PaCO2 = 40.0 +/- 0.1 Torr, mean +/- 95% confidence limits, and VA/VCO2 = 21.6 +/- 0.1). CBX rats showed 1) chronic hypoventilation with respiratory acidosis, which was maintained for at least 75 days after surgery (PaCO2 = 48.4 +/- 1.1 Torr and VA/VCO2 = 17.9 +/- 0.4), 2) hyperventilation in response to acute hyperoxia vs. hypoventilation in intact rats, 3) an attenuated increase in VA/VCO2 in acute hypoxemia (arterial PO2 approximately equal to 49 Torr), which was 31% of the 8.7 +/- 0.3 increase in VA/VCO2 observed in control rats, 4) no ventilatory acclimatization between 1 and 24 h hypoxia, whereas intact rats had a further 7.5 +/- 1.5 increase in VA/VCO2, 5) a decreased PaCO2 upon acute restoration of normoxia after 24 h hypoxia in contrast to an increased PaCO2 in controls. We conclude that in rats carotid body chemoreceptors are essential to maintain normal eupneic ventilation and to the process of ventilatory acclimatization to chronic hypoxia.

Presynaptic neurotransmitter and chemosensory responses to natural stimuli

1984 ◽  
Vol 56 (2) ◽  
pp. 447-453 ◽  
Author(s):  
M. Pokorski ◽  
S. Lahiri
Keyword(s):  
Carotid Body ◽  
Nerve Terminals ◽  
Cholinergic Mechanism ◽  
Natural Stimuli ◽  
Release Of Acetylcholine ◽  
Ventilatory Effects ◽  
Presynaptic Nerve Terminals ◽  
Carotid Body Chemoreceptors ◽  
Arterial Po2 ◽  
Stimulation Of

We investigated the hypothesis that release of acetylcholine from presynaptic nerve terminals in the carotid body may be responsible for the excitation of carotid body chemoreceptors by hypoxia and hypercapnia and central ventilatory stimulation by hypercapnia. 4-Aminopyridine, an agent known to release presynaptic transmitters including acetylcholine, was administered intravenously (1 mg X kg-1) or by close intra-arterial injection to the carotid body (200 micrograms) in anesthetized cats. 4-Aminopyridine did not change the carotid chemosensory responses to any arterial PO2 or PCO2 levels studied, whereas it stimulated ventilation at all arterial PO2 and PCO2 levels. Atropine blocked the ventilatory effects of 4-aminopyridine but not the responses to hypoxia and hypercapnia. The results add to the evidence, which shows that the presynaptic cholinergic mechanism is not germane to carotid body chemoreception. Also, acetylcholine does not seem to mediate the central hypercapnic stimulation of ventilation.

Increased propensity for apnea via dopamine-induced carotid body inhibition in sleeping dogs

2005 ◽  
Vol 98 (5) ◽  
pp. 1732-1739 ◽  
Author(s):  
Bruno J. Chenuel ◽  
Curtis A. Smith ◽  
Kathleen S. Henderson ◽  
Jerome A. Dempsey
Keyword(s):  
Steady State ◽  
Carotid Body ◽  
Pressure Support Ventilation ◽  
Pressure Support ◽  
Ventilatory Response ◽  
Rapid Eye Movement Sleep ◽  
The Difference ◽  
End Tidal ◽  
Carotid Body Chemoreceptors

We determined the effects of specific carotid body chemoreceptor inhibition on the propensity for apnea during sleep. We reduced the responsiveness of the carotid body chemoreceptors using intravenous dopamine infusions during non-rapid eye movement sleep in six dogs. Then we quantified the difference in end-tidal Pco2 (PetCO2) between eupnea and the apneic threshold, the “CO2 reserve,” by gradually reducing PetCO2 transiently with pressure support ventilation at progressively increased tidal volume until apnea occurred. Dopamine infusions decreased steady-state eupneic ventilation by 15 ± 6%, causing a mean CO2 retention of 3.9 ± 1.9 mmHg and a brief period of ventilatory instability. The apneic threshold PetCO2 rose 5.1 ± 1.9 Torr; thus the CO2 reserve was narrowed from −3.9 ± 0.62 Torr in control to −2.7 ± 0.78 Torr with dopamine. This decrease in the CO2 reserve with dopamine resulted solely from the 20.5 ± 11.3% increase in plant gain; the slope of the ventilatory response to CO2 below eupnea was unchanged from normal. We conclude that specific carotid chemoreceptor inhibition with dopamine increases the propensity for apnea during sleep by narrowing the CO2 reserve below eupnea. This narrowing is due solely to an increase in plant gain as the slope of the ventilatory response to CO2 below eupnea was unchanged from normal control. These findings have implications for the role of chemoreceptor inhibition/stimulation in the genesis of apnea and breathing periodicity during sleep.

Interspike interval dependency from arterial chemoreceptors

1985 ◽  
Vol 59 (5) ◽  
pp. 1566-1570 ◽  
Author(s):  
D. F. Donnelly ◽  
W. F. Nolan ◽  
E. J. Smith ◽  
R. E. Dutton
Keyword(s):  
Carotid Body ◽  
Interspike Interval ◽  
Correlation Coefficients ◽  
Feedback System ◽  
Serial Dependence ◽  
Control Series ◽  
First Order ◽  
System Operating ◽  
Poisson Type

The carotid body impulse generator has been previously characterized as a Poisson-type random process. We examined the validity of this characterization by analyzing sinus nerve spike trains for interspike interval dependency. Fifteen single chemoreceptive afferents were recorded in vivo under hypoxic-hypercapnic conditions, and approximately 1,000 consecutive interspike intervals for each fiber were timed and analyzed for serial dependence. The same set of intervals placed in shuffled order served as a control series without serial dependence. The original spike interval trains showed significantly negative first-order serial correlation coefficients and less variability in joint interval distributions than did the shuffled interval trains. These results suggest that the chemoreceptor afferent train is not random and may reflect a negative feedback system operating within the carotid body that limits variation about a mean frequency.

Excitatory amino acid receptors in commissural nucleus of the NTS mediate carotid chemoreceptor responses

1993 ◽  
Vol 264 (1) ◽  
pp. R41-R50 ◽  
Author(s):  
A. Vardhan ◽  
A. Kachroo ◽  
H. N. Sapru
Keyword(s):  
Amino Acid ◽  
Carotid Body ◽  
Excitatory Amino Acid ◽  
Minute Ventilation ◽  
Neuronal Cell ◽  
Excitatory Amino Acid Receptors ◽  
Amino Acid Receptors ◽  
Neuronal Cell Bodies ◽  
Carotid Body Chemoreceptors ◽  
Stimulation Of

Stimulation of carotid body chemoreceptors by saline saturated with 100% CO2 elicited an increase in mean arterial pressure, respiratory rate, tidal volume, and minute ventilation (VE). Microinjections of L-glutamate into a midline area 0.5-0.75 mm caudal and 0.3-0.5 mm deep with respect to the calamus scriptorius increased VE. Histological examination showed that the site was located in the commissural nucleus of the nucleus tractus solitarii (NTS). The presence of excitatory amino acid receptors [N-methyl-D-aspartic acid (NMDA); kainate, quisqualate/alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) and trans 1-amino-cyclopentane-trans-1,3-dicarboxylic acid (ACPD)] in this area was demonstrated by microinjections of appropriate agonists. Simultaneous blockade of NMDA and non-NMDA receptors by combined injections of DL-2-aminophosphonoheptanoate (AP-7; 1 nmol) and 6,7-dinitro-quinoxaline-2,3-dione (DNQX; 1 nmol) abolished the responses to stimulation of carotid body on either side. Combined injections of AP-7 and DNQX did not produce a nonspecific depression of neurons because the responses to another agonist, carbachol, remained unaltered. Inhibition of the neurons in the aforementioned area with microinjections of muscimol (which hyperpolarizes neuronal cell bodies but not fibers of passage) also abolished the responses to subsequent carotid body stimulation on either side.(ABSTRACT TRUNCATED AT 250 WORDS)

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