Abolition of ventilatory response to inhaled CO₂ by neurological lesions

Abstract

Evidence is presented for the localization of central chemoreceptors. Respiratory minute volume was measured in rats after surgical procedures that removed known or presumed chemoreceptor areas in various combinations. In each case the control ventilation was measured during inhalation of 100% O2, and the test response was the steady state ventilation on breathing O2 with either 5% or 10% CO2 added. To test completeness of carotid chemoreceptor denervation, 6–8% O2 in N2 was employed. Our data show that ventilatory response to inhaled CO2 is abolished if three lesions are produced simultaneously. The lesions must destroy the carotid chemoreceptor, a region surrounding and including the area postrema in the medulla, and diencephalic tissue rostral to a line passing through the posterior commissure dorsally and just behind the optic chiasm ventrally. If any of the three remains intact the ventilatory response is indistinguishable from that of the anesthetized, unoperated control animal. Minute volume is not abnormally low in the CO2-insensitive animal, and superficially the respiratory pattern is of normal rate and depth. A speculative hypothesis regarding the mechanism of function of the non-neural tissue of the area postrema is proposed.

Morphine Depression and Tolerance of Nerve‐induced Parotid Secretion

“…Over a 10min period the mean expired volume measured in 19 animals was 145 + 4 ml/min. This figure is in agreement with previous reports by Guyton (1947), Masland & Yamamoto (1962) and Bartle4t, & Tenney (1970). The resting pulmonary minute volume of the control or naive rats was depressed substantially by morphine (1 to 2 mg/kg).…”

Ventilatory Depression in Naive and Tolerant Rats in Relation to Plasma Morphine Concentration

“…This figure is in agreement with previous reports by Guyton (1947), Masland & Yamamoto (1962) and Bartlett & Tenney (1963).…”

“…The action of morphine on the pulmonary minute volume (PMV) in naive animals The PMV was measured over a 10 min period in anaesthetized adult male rats maintained at a constant temperature of 37 + 1°C; the mean minute volume measured in 19 animals amounted to 145 + 4 ml/min BTPS. This figure is in agreement with previous reports by Guyton (1947), Masland & Yamamoto (1962) and Bartlett & Tenney (1963).…”

Respiratory responses to electrical and chemical stimulation of the area postrema in the rabbit.

“…A role in respiration for this most caudally placed circumventricular organ had been suggested in the early 1960s (Masland & Yamamoto, 1962) which was later refuted (Florez & Borison, 1967). However, a respiratory role for the AP is not surprising in view of its well-established emetic function (Borison & Wang, 1953; for review, see Borison, 1989).…”

“…In the early 1960s, it was reported that neurological lesions involving the AP caused an abolition of ventilatory response to inhaled CO2 (Masland & Yamamoto, 1962) but this was refuted in a later study (Florez & Borison, 1967). To our knowledge, there has been only one study which has demonstrated the effects on respiratory function evoked by chemical stimulation of the AP in the cat (Gatti, Souza, da Silva, Quest & Gillis, 1985).…”