Role of cerebral fluids in control of respiration as studied in unanesthetized goats

Abstract

Respiratory responses to inhaled CO2 were measured in unanesthetized goats during repeated perfusions of the ventriculocisternal system through chronically implanted cannulas. [HCO3–] and pH were measured in carotid loop blood and cisternal outflow. Average steady-state alveolar ventilation increased fourfold when cerebrospinal fluid (CSF)-[HCO3–] was reduced from 30 to 15 mm/liter at constant, normal CO2 pressure or threefold when CSF pH changed from 7.32 to 7.21 at constant, normal CSF-[HCO3–]. Sensitivity was two- to sevenfold greater than reported for anesthetized animals. At constant CSF pH the ventilatory response to inhaled CO2 was 60% of the isobicarbonate response. Pco2 in cisternal outflow was shown to approximate that in cerebral tissue. HCO3– flux was measured as a function of CSF-[HCO3–] and concentration profiles between CSF and capillary blood were considered. Alveolar ventilation is a single linear function of [H+] in tissue fluid located two-thirds to three-fourths of the distance along the functional concentration gradient of HCO3– between CSF and blood at all values of Pco2 and CSF-[HCO3–] which we investigated.

Central chemosensitivity and the reaction theory.

“…The blood flow in the choroid plexus is extremely high (Page, Funsch, Brennan & Hernandez, 1980) (Pappenheimer, Fencl, Heisey & Held, 1965; Carman, Severinghaus, Richardson, Singer & Shnider, 1965;Kronenberg & Cain, 1968;Fencl, 1971). In cats it was even less, for example, 20% (Ahmad et al 1976).…”

Inhibition of Monocarboxylate Transporter 2 in the Retrotrapezoid Nucleus in Rats: A Test of the Astrocyte–Neuron Lactate-Shuttle Hypothesis

“…The buffering power of the extracellular space is low (Pappenheimer et al, 1965), and changes in either lactate efflux or influx in astrocytes or neurons can result in significant reciprocal fluctuations in pH. Blood and brain tissue pH are maintained at constant levels by central respiratory chemoreceptors located primarily in the medulla.…”

The active transport of 5‐hydroxyindol‐3‐ylacetic acid and 3‐methoxy‐4‐hydroxyphenylacetic acid from a recirculatory perfusion system of the cerebral ventricles of the unanaesthetized dog

“…Leusen (1950Leusen ( , 1954a, and Bering & Sato (1963) in dogs ;Feldberg & Fleischhauer (1960 in cats; Cserr (1965), and Palaic,398 G. W. ASHCROFT, R. C. DOW AND A. T. B. MOIR Page & Khairallah (1967) in rats; and Bradbury & Davson (1964,1965 in rabbits. The only experiments utilizing this technique in conscious animals have been by Pappenheimer and his co-workers in conscious goats (Pappenheimer, Heisey & Jordan, 1961;Pappenheimer, Heisey, Jordan & Downer, 1962;Heisey, Held & Pappenheimer, 1962;Pappenheimer, Fencl, Heisey & Held, 1965) and by Manuilov (1958) in conscious dogs. There would, however, be advantages in a study of conscious animals by means of a recirculatory perfusion system.…”