Dual influence of temperature on compound nerve action potential

The permeability of the blood-brain barrier has been measured using a technique which is independent of blood flow and is sufficiently accurate to monitor the penetration of weakly permeant substances.The permeability of the blood-brain barrier to [¹⁴C]sucrose has been measured in rats anaesthetised with either urethane or pentobarbitone (Nembutal). The values obtained from urethane-anaesthetised untreated rats were slightly lower, thus demonstrating the suitability of urethane as an anaesthetic for blood-brain barrier experiments.The permeability of the barrier has been measured in rats which had been drinking 7.5% ethanol for 6 months, or had been administered an anaesthetic dose of ethanol, or both. No statistically significant difference was found between the permeability measurements in rats subjected to any of these treatments. Positive controls in which 0.3 ml of a 30% ethanol solution was injected into the internal carotid artery demonstrated the sensitivity of the employed technique. Thus it was found that the blood-brain barrier does not weaken with respect to sucrose when the blood ethanol concentration reaches an anaesthetic level.