Effect of Sodium Pentobarbital on the Apparent Turnover of Acetylcholine in Different Brain Regions

Abstract

The turnover rate of acetylcholine (ACh) was measured in six different brain regions in the mouse following pulse injection of radioactive choline (Ch) and killing of the animals by microwave irradiation of the head (0.25 s, 5 kW). The time course of the change in ³H-ACh/³H-Ch ratio was linear 0–60 s in all brain regions after administration of ³H-Ch. Plots of the specific radioactivities (SA) of ACh and Ch versus time indicate a precursor-product relationship in all brain regions except the cerebellum both in control and sodium pentobarbital anesthesized animals. The turnover was highest in the striatum (55 nmol g^-1 min^-I), while in the cortex and hippocampus this value was approximately half (27 and 21 nmol-g^-1-min^-1). In the midbrain and medulla oblongata the turnover rates were only 11 and 10 nmol gr^-1 min^-1. Sodium pentobarbital anesthesia reduced specifically the turnover in the cortex and hippocampus to about 60 to 70 per cent.