Acute Carotid Research Articles

Hyperventilation in ponies at the onset of and during steady-state exercise.

We studied blood gases in ponies to assess the relationship of alveolar ventilation (VA) to pulmonary CO2 delivery during moderate treadmill exercise. In normal ponies for 1.8, 3, or 6 mph, respectively, partial pressure of CO2 in arterial blood (PaCO2) decreased maximally by 3.1, 4.4, and 5.7 Torr at 30-90 s of exercise and remained below rest by 1.4, 2.3, and 4.5 Torr during steady-state (4-8 min) exercise (P less than 0.01). Partial pressure of O2 in arterial blood (PaO2) and arterial pH, (pHa) also reflected hyperventilation. Mixed venus CO2 partial pressure (PVCO2) decreased 2.3 and 2.9 Torr by 30 s for 3 and 6 mph, respectively (P less than 0.05). In work transitions either from 1.8 to 6 mph or from 6 mph to 1.8 mph, respectively, PaCO2 either decreased 3.8 Torr or increased 3.3 Torr by 45 s of the second work load (P less than 0.01). During exercise in acute (2-4 wk) carotid body denervated (CBD) ponies at 1.8, 3, or 6 mph, respectively, PaCO2 decreased maximally below rest by 9.0, 7.6, and 13.2 Torr at 30-45 s of exercise and remained below rest by 1.3, 2.3, and 7.8 Torr during steady-state (4-8 min) exercise (P less than 0.1). In the chronic (1-2 yr) CBD ponies, the hypocapnia was generally greater than normal but less than in the acute CBD ponies. We conclude that in the pony 1) VA is not tightly matched to pulmonary CO2 delivery during exercise, particularly during transitional states, 2) the exercise hyperpnea is not mediated by PaCO2 or PVCO2, and 3) during transitional states in the normal pony, the carotid bodies attenuate VA drive thereby reducing arterial hypocapnia.

Hyperpnea of exercise at various PIO2 in normal and carotid body-denervated ponies

We studied the effect of changes in inspired [O2] on partial pressure of CO2 in arterial blood (PaCO2) during treadmill exercise (3 mph, 3% grade) in normal, acute (+2-4 wk), and chronic (+1-2 yr) carotid body-denervated (CBD) ponies. In all studies, PaCO2 decreased (P less than 0.01) from rest during exercise, reaching a nadir usually between 15 and 30 s of exercise. During normoxia [partial pressure of O2 in arterial blood (PaO2) approximately 95 Torr], the PaCO2 nadir was 2.3 +/- 0.6 Torr below resting level in normal ponies, but the nadir was greater (P less than -0.01) in acute (delta = 6.4 +/- 0.8 Torr) and chronic (delta = -4.7 +/- 1.1 Torr) CBD ponies. Hyperoxia (PaO2 approximately 180 Torr) accentuated (P less than 0.01) the hypocapnia only in the normal ponies (delta = -6.3 +/- 1.0 Torr). In contrast, hypoxia (PaO2 48 Torr) attenuated (P less than 0.01) the exercise-induced hypocapnia by 3-5 Torr in all ponies. Usually PaCO2 gradually increased after 30 s of exercise, reaching a stable level 1-3 Torr below rest by about 2 min (P less than 0.05). Tidal volume (VT) increased from rest during the first 15 s of exercise only when there was a large decrease in PaCO2. Recovery of PaCO2 after 30 s of exercise was associated with a decrease in VT toward rest. We concluded the following. 1) The accentuated hypocapnia caused by eliminating (CBD) or reducing (hyperoxia) carotid chemoreceptor activity suggests that the chemoreceptors normally dampen alveolar ventilation (VA) at the onset of exercise. 2) Attenuation of the hypocapnia at the onset of exercise by hypoxia in CBD ponies suggests that a direct CNS effect of hypoxia dampens VA. 3) Mechanisms tending to minimize the hypocapnia during exercise appear to adjust VA by modulating VT.

Redistribution of intrarenal blood flow after carotid artery occlusion in the rat.

As indicated by changes in microsphere distribution in the rat, acute bilateral carotid artery occlusion (CAO) was found to cause a small but significant increase in outer cortical flow fraction. When renal perfusion pressure was kept constant, no redistribution occurred upon CAO. In denervated kidneys the redistribution induced by CAO did not differ from that observed in contralateral control kidneys. Animals pretreated with prostaglandin inhibitors showed a significant redistribution in the 'unprotected' right kidney and a minor increase in outer cortical flow fraction in the normotensive kidney. It is concluded that: (1) the increase in outer cortical flow fraction induced by CAO in the rat is due to an increase in perfusion pressure, and (2) that this redistribution is independent of sympathetic vasoconstrictor stimuli, catecholamines and prostaglandins.

Hemodynamic and renal functional changes after acute unilateral nephrectomy in the dog: role of carotid sinus baroreceptors.

We examined the role of the carotid sinus baroreceptors in the hemodynamic and renal functional changes initiated by acute unilateral nephrectomy (AUN). In 15 anesthetized dogs, AUN caused increases in sodium (UNaV) and potassium excretion (UKV) without significant changes in GFR, renal blood flow, or mean arterial pressure. Cardiac output (CO) was measured in five of these animals and decreased from 2.5 +/- 0.2 to 1.9 +/- 0.3 liter/min as total peripheral resistance (TPR) increased. In 11 dogs with bilateral acute surgical carotid sinus denervation, AUN failed to cause any change in renal hemodynamics, UNaV, or UKV that could be distinguished from sham-operated time controls. CO was measured in seven of these dogs and also did not change. AUN caused an immediate, transient elevation in blood pressure that returned to control levels 15 min after nephrectomy. When bilateral carotid occlusion (BCO) was carried out prior to AUN in animals with intact carotid sinus baroreceptors, AUN again caused an immediate increase in blood pressure but no changes in CO or electrolyte excretion. In separate studies, AUN increased UNaV and UKV significantly; when BCO was then carried out after AUN, cation excretion remained elevated. In seven dogs undergoing continuous perfusion of the carotid circulation bilaterally at constant pressure, AUN again failed to increase cation excretion despite a 30 mmHg rise in arterial blood pressure. These studies demonstrate that AUN fails to initiate hemodynamic or compensatory renal functional changes in dogs with bilateral carotid sinus denervation or in animals in which intact baroreceptors are shielded from the systemic circulation by BCO or perfusion at constant pressure, indicating the importance of these baroreceptors in the early changes after AUN.

Altered cerebral glucose utilization following blood-brain barrier opening by hypertonicity or hypertension

The blood-brain barrier (B-BB) in conscious rats was opened to Evans blue dye by carotid infusion of a 1.8 m arabinose solution or by acute unilateral carotid hypertension, following which [ 14C]2-deoxy- d-glucose was injected intravenously. Rats were killed 45 min later, and autoradiographs were made from frozen brain sections. Focal areas of increased optical density, or “hot spots,” were noted in brain regions when the B-BB was opened but were absent when B-BB integrity was unaffected. These hot spots, which represented accumulations of brain radioactivity, were not prevented by diet-induced hypokalemia or by systemic pretreatment with high doses of phenoxybenzamine or propranolol. Their cause remains unclear, but their induction by both hypertensive and osmotic B-BB opening suggests that B-BB damage, regardless of cause, can markedly disturb cerebral metabolism.

Vascular distensibility in the eye.

Distensibility of the intraocular vascular bed was studied in the living cat eye by measuring the alterations of ciliary artery blood pressure and intraocular pressure induced by varying degrees of acute common carotid artery occlusion. A semilogarithmic relationship was found between alterations in ciliary artery blood pressure and ocular volume changes. The slope of this relationship, termed the coefficient of vascular rigidity, was found to be approximately 1.5 times the ocular rigidity in all eyes tested. Similar values were obtained by direct perfusion of the ophthalmic artery in enucleated cat eyes when alterations in vascular perfusion pressure were induced from a baseline value of 50 mm Hg. The results indicate that measurements of intraocular volume changes after acute common carotid compression may offer a clinical method of determining vascular rigidity in the eye.

Nitrous oxide: an anesthetic for experiments in cats.

ARTICLESNitrous oxide: an anesthetic for experiments in catsJL Venes, WF Collins, and A TaubJL Venes, WF Collins, and A TaubPublished Online:01 Jun 1971https://doi.org/10.1152/ajplegacy.1971.220.6.2028MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByUltrasonic Neuromodulation Causes Widespread Cortical Activation via an Indirect Auditory MechanismNeuron, Vol. 98, No. 5On the use of isofluorane as an anaesthetic for visual neurophysiologyExperimental Brain Research, Vol. 88, No. 1Effects of nitrous oxide on the somatosensory evoked response in catsJournal of Anesthesia, Vol. 4, No. 1Harmonic basis functions for spatial coding in the cat striate cortex2 June 2009 | Visual Neuroscience, Vol. 3, No. 4Spatial organization of subfields in receptive fields of cells in cat striate cortexVision Research, Vol. 29, No. 7Heart rate response to atropine in humans anaesthetized with five different techniquesCanadian Journal of Anaesthesia, Vol. 35, No. 5The uncertainty principal in visionNeurophysiology, Vol. 18, No. 3Cerebrovascular reserve in the cat after acute bilateral carotid occlusion26 September 2008 | Archives Internationales de Physiologie et de Biochimie, Vol. 95, No. 3Cerebrovascular reserve in the cat after acute bilateral carotid occlusion26 September 2008 | Archives Internationales de Physiologie et de Biochimie, Vol. 95, No. 4Effect of diltiazem-induced hypotension on normal and increased intracranial pressure of catsCanadian Anaesthetists’ Society Journal, Vol. 33, No. 5Concentration-dependent suppression by β-adrenergic antagonists of the shift in ocular dominance following monocular deprivation in kitten visual cortexNeuroscience, Vol. 18, No. 4Cortical acetylcholine efflux with hypercapnia and nociceptive stimulationBrain Research, Vol. 338, No. 2Plasticity in cat visual cortex restored by electrical stimulation of the locus coeruleusNeuroscience Research, Vol. 2, No. 5Immobilization of rats modifies the response of striatal neurons to dexamphetaminePharmacology Biochemistry and Behavior, Vol. 21, No. 1Enhanced binocular interaction in the visual cortex of normal kittens subjected to intracortical norepinephrine perfusionBrain Research, Vol. 302, No. 1Functional recovery of cortical neurons as related to degree and duration of ischemiaAnnals of Neurology, Vol. 14, No. 3Long Term Effects of Spinal Cord Lesions on the Configuration of Somatosensory Evoked Potentials1 July 1983 | Clinical Electroencephalography, Vol. 14, No. 3Effect of Nitrous Oxide on Local Cerebral Glucose Utilization in Rats29 June 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 2, No. 4An Animal Model for Investigating the Clinical Utility of Somatosensory Evoked Potentials1 July 1982 | Clinical Electroencephalography, Vol. 13, No. 3Cerebral oxygen availability and blood flow during middle cerebral artery occlusion: effects of pentobarbital.Stroke, Vol. 12, No. 6Peripheral nerve fiber and spinal cord pathway contributions to the somatosensory evoked potentialExperimental Neurology, Vol. 73, No. 3Nitrous oxide alters oxidative metabolic activities of rat neocortex in situBrain Research, Vol. 213, No. 2Comparison between hydrogen clearance and microsphere technique for rCBF measurement.Stroke, Vol. 12, No. 2Nitrous oxide modifies visual responses in the cat retina, striate cortex and superior colliculusBrain Research, Vol. 193, No. 2Coupling between neuronal activity and focal blood flow in experimental seizuresElectroencephalography and Clinical Neurophysiology, Vol. 47, No. 4Preservation of binocularity after monocular deprivation in the striate cortex of kittens treated with 6-HydroxydopamineThe Journal of Comparative Neurology, Vol. 185, No. 1Inadequacy of nitrous oxide/oxygen mixtures for maintaining anaesthesia in cats: satisfactory alternativesPain, Vol. 5, No. 2Are field potentials an appropriate method for demonstrating connections in the brain?Experimental Neurology, Vol. 60, No. 3Spatial frequency selectivity of periodic complex cells in the visual cortex of the catVision Research, Vol. 18, No. 6Dorsal column stimulation: Its effect on medial bulboreticular unit activity evoked by noxious stimuliExperimental Neurology, Vol. 54, No. 2Effect of nitrous oxide anesthesia upon cerebral energy metabolismJournal of Neurochemistry, Vol. 28, No. 1Medial bulboreticular response to peripherally applied noxious stimuliExperimental Neurology, Vol. 42, No. 2Der Einflu� von Stickoxydul und Chloralose-Urethan auf den Kreislauf und die pr�ganglion�re Sympathicusaktivit�t der KatzeNaunyn-Schmiedeberg's Archives of Pharmacology, Vol. 284, No. 1Variation in the response latency of cat retinal ganglion cellsVision Research, Vol. 13, No. 4Evoked bulbar reticular unit activity following delta fiber stimulation of peripheral somatosensory nerve in catExperimental Neurology, Vol. 37, No. 3Evoked cerebral cortical activity from small peripheral nerve fibers in catElectroencephalography and Clinical Neurophysiology, Vol. 33, No. 2 More from this issue > Volume 220Issue 6June 1971Pages 2028-2031 Copyright & PermissionsCopyright © 1971 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1971.220.6.2028PubMed5087855History Published online 1 June 1971 Published in print 1 June 1971 Metrics

Graphic analysis of the ocular pulse in carotid occlusion.

The ocular pulse was recorded from the surface of rabbit eyes by the suction cup method. Graphic analytical techniques utilized in plethysmographic studies of peripheral pulses were applied to the ocular pulse, and the effects of acute and chronic unilateral common carotid occlusion and stenosis were noted. Acute common carotid ligation caused a marked reduction in the amplitude of the homolateral ocular pulse, disappearance of the dicrotic notch, delay in crest time, and a reduction in the steepness of the anacrotic and catacrotic slopes. Unilateral stenotic lesions had similar but less marked effects. The degree of reduction of pulse amplitude was related directly to the amount of carotid stenosis. The amplitude of the ocular pulse spontaneously returns to normal within five months of acute common carotid ligation.

Ophthalmodynamometry and ocular pulse studies in carotid occlusion.

Ophthalmodynamometry and ocular pulse studies were performed on rabbits with surgically induced acute and chronic unilateral common carotid occlusion. Ocular pulses were recorded by the suction cup technique at intraocular pressures between 8 and 140 mm Hg and were correlated with choroidal and retinal diastolic and systolic pressures. Choroidal systole and diastole were found to be approximately 14 mm Hg less than corresponding retinal values. Peak ocular pulse amplitudes were obtained at intraocular pressures approximately one-half retinal diastolic values. The ocular pulse amplitude was more sensitive than ophthalmodynamometry in detecting both acute and chronic carotid occlusions.

Oculosphygmography in acute and chronic carotid insufficiency.

CRANIAL arterial insufficiency is well known to affect the circulation to the eye, as demonstrated by measurements of retinal arterial pressure, 1 fluorescein circulation time, 2,3 and ocular tonography. 4 Although first recorded in 1928, 5 ocular pulsations have not been studied extensively, and the observation that carotid insufficiency dampened their amplitude was reported only in 1964. 6 A series of patients is described in this report from which some judgment can be made about the value of oculosphygmography in diagnosing carotid insufficiency and also in predicting the adequacy of collateral circulation when carotid ligation is planned. Materials and Methods At the time of initial examination, 25 patients had no stenosis of the extracranial carotid arteries as great as 50%; in 12, the lumen of one carotid artery was narrowed 50% or greater; in 9 patients, one carotid artery was completely obstructed; in 5, one artery was stenotic and

Chronic effects of carotid sinus denervation, cervical vagotomy and aortic depressor nerve section on aldosterone and sodium excretion.

Carotid sinus denervation in dogs and aortic depressor nerve section in rabbits were without effect on urinary aldosterone and sodium (Na) excretion. Also, adrenal vein aldosterone output following both acute and chronic carotid sinus denervation was unaltered. Constriction of the thoracic inferior vena cava in dogs with carotid sinus denervation resulted in hyperaldosteronuria, marked Na retention and ascites, a response in no way different from that occurring in intact dogs. Subsequent unilateral cervical vagotomy had no detectable influence on the hyperaldosteronism and Na retention. Section of the remaining vagus resulted in a slight increase in Na excretion, but Na balance remained positive and ascites continued to accumulate. Since the increase in Na excretion was meager and the continued high rate of aldosterone output occurred in two of three dogs, it seems unlikely that the vagus constitutes an appreciable part of an afferent nervous limb. The data offer no support for the concept that receptors concerned with the control of aldosterone secretion or Na excretion are located in the aortic arch or carotid sinus.

Effects of unilateral and bilateral carotid arterial occlusions in monkeys.

ConclusionsIt is concluded that acute permanent unilateral complete carotid (common, internal and external) or bilateral common carotid occlusions are well tolerated by monkeys. However, bilateral acute permanent complete carotid (common, internal and external) occlusions are only occasionally well tolerated. Bilateral complete carotid occlusions are more likely to be well tolerated if right and left sides are ligated separatel with a prolonged interval (over 6 weeks) between the 2-sided occlusions to permit establishment of adequate collateral circulation.