Vladimir Fencl

Naloxone does not affect ventillatory responses to hypoxia and hypercapnia in rats

Ventilatory responses (tidal volume, respiratory frequency, and minute ventilation) to steady-state hypoxia and steady-state hypercapnia were measured plethysmographically in awake unrestrained adult rats, before and after subcutaneous injection of placebo (saline) naloxone in doses up to 5.0 mg/kg. Naloxone did not alter the ventilatory responses to hypoxia or hypercapnia.

Carbon Dioxide in Cerebral Extracellular Fluids

The extravascular extracellular compartment of the cerebral fluids consists of the cerebral interstitial fluid (cISF) and of the cerebrospinal fluid (CSF). Both these fluids are continuously formed from, and returned to, the blood plasma (DAVSON [1967]). The rate of formation and bulk absorption of CSF is slow, about 0.5% of its total volume per minute (HEISEY et al. [1962]). In cISF the turnover is probably faster (FENCL et al. [1966]). CSF in the ventricles is separated from cISF by the ependyma; on the outer surface of the brain the separation between CSF and cISF is formed by pia-glia. Both these boundaries permit exchange by free diffusion of even large molecules, between cISF and the CSF in large cerebral cavities (BRIGHTMAN et al. [1970]).