Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Chemoreceptor”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMed1971

Abnormal chemoreceptor response to hypoxia in patients with tabes dorsalis.

Nine patients with tabes dorsalis and one patient with diabetic autonomic neuropathy were subjected to hypoxia to test the integrity of their carotid chemoreceptors. Ventilation and pulse rate changes were monitored and compared with those of a group of normal subjects of comparable age and sex. Four patients had a completely negative response to hypoxia, and the changes in ventilation in the group of patients as a whole were significantly less than in the control subjects. The results indicate that some patients with autonomic denervation are unable to adjust their respiratory system in response to hypoxia.

Aged↗
PubMed1987

Tachycardia of carotid chemoreceptors originates in apneic asphyxia in dogs.

Using various anesthetics, we investigated the heart rate changes resulting from apneic asphyxia in paralyzed artificially ventilated dogs with 1) low control heart rate (LCHR) and 2) high control heart rate (HCHR). We observed that apneic asphyxia produced by stopping the ventilation pump for 1 min evoked tachycardia in dogs with LCHR and bradycardia in dogs with HCHR. In dogs breathing 100% O2 in the preapneic period, the tachycardia response was almost wholly abolished, whereas the bradycardia response was attenuated. Intracarotid injection of sodium cyanide induced a tachycardia response in dogs with LCHR and a bradycardia response in dogs with HCHR. The results suggest that 1) apneic asphyxia evokes tachycardia or bradycardia response depending on whether the resting cardiac vagal tone is high or low, respectively, and 2) both types of heart rate responses are in part due to stimulation of carotid chemoreceptors.

Animals↗
PubMed1984

Dopaminergic efferent inhibition of carotid body chemoreceptors in chronically hypoxic cats.

The observations that the dopamine concentration of the carotid body and efferent inhibition of carotid chemoreceptors are increased during chronic hypoxia led to the hypothesis that the inhibition was due to the effect of an increased dopamine release by the activity of carotid sinus nerve (CSN) efferents. The hypothesis was tested by measuring the effect of dopamine receptor blockade on efferent inhibition of carotid chemosensory responses to graded levels of arterial O2 partial pressure in chronically hypoxic and normoxic cats. Chronically hypoxic cats were prepared by exposing the cats to 10% O2 at sea level for 30-34 days. Carotid chemosensory activity was first measured from a slip of an otherwise intact CSN. The measurements were then repeated after sectioning the remaining nerve trunk. The effect of sectioning the CSN provided the measure of efferent inhibition. In each group of cats the effects of sectioning the CSN with and without dopamine receptor blockade by haloperidol were also studied. CSN section augmented the chemosensory responses in the chronically hypoxic cats. Haloperidol, a dopamine antagonist, augmented the responses further, indicating that a part of the endogenous dopamine effect was independent of the CSN efferents. After haloperidol treatment CSN section did not influence the chemosensory responses. This study confirmed that the efferent inhibition significantly increased in the chronically hypoxic cats and demonstrated that haloperidol blocked the efferent inhibition, suggesting that the mechanism of the augmented inhibition is dopaminergic.

Animals↗
PubMed1981

Effect of carotid chemoreceptor denervation on breathing in utero and after birth.

The influence of the carotid bodies on fetal breathing activity in utero and on the establishment of postnatal breathing was studied. The electrocorticogram, the electromyogram of the lateral rectus and postural muscles, and tracheal and arterial pressures were monitored on chronically prepared intact and carotid sinus-denervated fetal lambs. The denervated fetuses required a longer time for recovery from the operation, but thereafter the sleeping and breathing behavior was similar to that of the control group. Four of the carotid sinus-denervated fetuses were allowed to be delivered spontaneously, and all established regular postnatal respiration despite conclusive evidence of nonfunctional carotid bodies. These experiments indicate that the fetal carotid chemoreceptors are not essential for the spontaneous intrauterine breathing activity during rapid-eye-movement sleep nor for the establishment of effective breathing at birth.

Animals↗
PubMed1982

Control of heart rate by carotid body chemoreceptors during diving in tufted ducks.

Previous work has shown that during forcible submersion of domestic ducks there is a gradual reduction in heart rate to 10-20% of its predive value after 45-60 s. Bilateral denervation of the carotid body chemoreceptors abolishes most of this bradycardia. By use of implanted radio transmitters it has been shown that in free-swimming tufted ducks, Aythya fuligula, there is an immediate reduction in heart rate, on spontaneous diving, from an elevated predive level. It then increases for a few seconds before it stabilizes at a level similar to that recorded when the duck is swimming fairly vigorously. The present study has shown that, following bilateral denervation of the carotid bodies, there is a significant increase in mean dive duration but no effect on the immediate reduction in heart rate on submersion. Heart rate is, however, significantly higher toward the end of spontaneous dives after carotid body denervation. Unlike the situation in mallards and their domesticated varieties, carotid body denervation has no effect on heart rate in tufted ducks during the first 40 s of forced dives. The carotid bodies therefore do not play the dominant role in cardiac control during submersion of diving ducks that has been suggested by work involving the forcible submersion of the mallard duck and its domesticated varieties.

Animals↗
PubMed1983

Carotid chemoreceptor regulation of expiratory duration.

We studied the effect of an experimentally augmented breath on the duration of expiration (TE) to test the hypothesis that within-breath reductions in alveolar partial pressure of CO2 (PACO2) delay the onset of the subsequent inspiration through a carotid chemoreceptor mechanism. Studies were performed in five carotid body intact (CBI) and three carotid body denervated (CBD) dogs during quiet wakefulness and nonrapid-eye-movement sleep. The vagus nerves were blocked in order to abolish vagal mechanisms capable of modulating TE. In CBI dogs, mechanically augmented breaths [mean tidal volume (VT), 149% of control] induced a mean decrease in PACO2 of 3.3 Torr and prolonged TE by 2.21 s to 127% of control (P less than 0.001). In contrast, in CBD dogs augmented breaths of comparable magnitude failed to change TE. Spontaneous sighs in fully intact dogs (mean VT, 369% of control) produced marked prolongation of TE (to 429% of control). In CBI dogs, there was a direct relationship between VT and the resulting TE across all experimental conditions (control, vagal blockade, augmented breaths, spontaneous sighs), whereas in CBD dogs, changes in VT failed to alter TE. The results indicate that the carotid bodies are able to induce within-breath alterations in TE and that such a mechanism can account for the prolongation of TE by vagal blockade and by spontaneous sighs.

Animals↗
PubMed1985

Interspike interval dependency from arterial chemoreceptors.

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.

Action Potentials↗
PubMed1983

The effect of intravenously administered almitrine, a peripheral chemoreceptor agonist, on patients with chronic air-flow obstruction.

Almitrine, a peripheral chemoreceptor agonist, was given intravenously in a dose of 0.5 mg/kg/h for 2 h in a randomized double-blind manner with placebo, to 11 patients with severe chronic air-flow obstruction and hypoxemia (SaO2 less than 90%). There was no significant placebo effect. Maximal respiratory effect occurred at the end of the almitrine infusion with an increase in ventilation from 8.2 + 0.9 to 11.6 + 1.5 L/min (mean +/- SEM), and improvements in SaO2 from 83 +/- 3 to 90 +/- 2%, in PaO2 from 48 +/- 2 to 55 +/- 3 mmHg, and in PaCO2 from 54 + 3 to 47 +/- 4 mmHg. Venous admixture was reduced from 38 +/- 4% to 22 +/- 3%. In 4 patients, blood gas values substantially improved, but there was no change in total ventilation for ventilatory pattern. This study of acute effects showed that almitrine improved arterial PO2 and PCO2 in patients with chronic air-flow obstruction both by increasing ventilation and by improving ventilation-perfusion relationships.

Almitrine↗
PubMed1997

Developmental changes in chemoreceptive control of gill ventilation in larval bullfrogs (Rana catesbeiana). II. Sites of O2-sensitive chemoreceptors

The time course of reflex changes in gill ventilation variables caused by a step-wise change in PO2 of inspired water and by the introduction of NaCN into inspired water was measured in two populations of unanesthetized larval bullfrogs (Rana catesbeiana) ­ one with intact gill arches and a second with bilateral ablation of the first gill arch. Developmental stages TK V­VII, IX­XI and XVII­XIX were examined. Inspiring hypoxic water or a pulse of NaCN significantly increased gill ventilation within 7 s in control larvae. Ablation of the first gill arches in larval R. catesbeiana eliminated the initial, quick response of gill ventilation to changes in the PO2 of inspired water and to the presence of NaCN in all three developmental groups. These data suggest that O2-sensitive chemoreceptors are located on the first gill arch and are responsible for the initial rapid ventilatory response. However, a slow response (>15 s) to changes in PO2 of inspired water persisted even after removal of the first gill arch. This response is far slower than the minimum blood circulation time (approximately 5­8 s as measured in all three groups), indicating that a second population of receptors is not directly monitoring arterial or venous blood. Instead, this second population of receptors is likely to be located 'behind' a significant diffusion barrier, possibly monitoring cerebrospinal fluid.

Journal Article↗
PubMed1975

Chemoreceptor reflexes in preterm infants: I. The effect of gestational and postnatal age on the ventilatory response to inhalation of 100% and 15% oxygen.

We studied 16 "healthy" preterm infants (birthweight, 1,000 to 2,000 gm) 94 times during postnatal life to define the effect of gestational and postnatal age on the ventilatory response to 100% and 15% oxygen. They were given air, then 100% oxygen for two and five minutes respectively (No.=63) or 21%, 15% and then 21% oxygen for five minutes each (No.=31). We measured respiratory minute and tidal volumes, frequency, heart rate, and alveolar PCO2 and PO2. We used the magnitude of the immediate change in ventilation during during 100% and 15% oxygen breathing to test peripheral chemoreceptor function. The immediate decrease in ventilation with 100% oxygen and the immediate increase in ventilation with 15% oxygen were statistically similar at different gestational and postnatal ages. The late increase in ventilation (five minutes) with 100% oxygen was also similar at different ages. However, the late decrease in ventilation with 15% oxygen was not present at 18 days of age. These findings suggest that: (1) the peripheral chemo-receptors are active at least from 28 weeks of gestation and are probably not important in triggering periodic breathing or apnea in preterm infants, and (2) the preterm infant matures his response to hypoxia and is able to sustain hyperventilation with low oxygen by 18 days of age.

Age Factors↗
PubMed1987

Purification and characterization of the S-adenosylmethionine:glutamyl methyltransferase that modifies membrane chemoreceptor proteins in bacteria.

The enzyme (EC 2.1.1.24) from Salmonella typhimurium that catalyzes the S-adenosylmethionine-dependent methyl esterification of glutamyl residues in membrane chemoreceptor proteins has been purified to homogeneity, and the nucleotide sequence of the gene coding for this protein, cheR, has been determined. The molecular weight, amino acid composition, and N-terminal amino acid sequence of the purified protein correspond to the values predicted from the sequence of the gene. The pure protein is a 33-kDa monomer. Kinetic studies indicate that, at levels of receptor and S-adenosylmethionine present in wild type cells, the transferase is nearly saturated. The enzyme has a relatively low turnover number, approximately 10 mol of methylester formed per mol of enzyme per min; and there appear to be only approximately 200 methyltransferase monomers per wild type cell.

Amino Acid Sequence↗
PubMed1986

Carotid body chemoreceptor excitation produced by carotid occlusion.

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.

Animals↗
PubMed1983

[Effects of colchicine, cyclic nucleotides and biogenic amines on the chemoreceptor apparatus of the tongue].

Colchycine considerably decreased sensitivity of the Rana temporaria tongue's chemoreceptors to adequate stimulation. The effect is reversible and can be abolished by administration of drugs initiating setting of the cells' microtubular apparatus: 3',5'-cAMP, theophylline, adrenaline as well as by activation of the sympathetic system. The restoring effect of these agents is specific since 2',3'-cAMP, 5'-AMP, serotonin, inosine, acetylcholine and 3,'5'-cGMP prove ineffective in restoring the reactions after colchycine administration although they do alter the activity of the receptors in normal conditions. The revealed colchycine-sensitive, 3',5'-cAMP-dependent process seems to be associated with the microtubular apparatus of the receptor cell. Its role in the receptor structures is discussed.

Adenosine Monophosphate↗
PubMedDate not supplied

Reduced blood pressure response to carotid body chemoreceptor stimulation in spontaneously hypertensive rats.

In nine 20-24-week-old spontaneously hypertensive rats (SHR) and twelve age-matched normotensive control rats (NCR) carotid body chemoreceptors were stimulated by acid saline injected into the common carotid artery. The animals were paralyzed and atropinized. The reflex blood pressure rise in NCR (27 +/- 2 mm Hg) was significantly greater than in SHR (4 +/- 2 mm Hg). We conclude that the sensitivity of the vascular-sympathetic component of the arterial chemoreflex is decreased in adult SHR.

Animals↗