THE DISTRIBUTION OF ACETYLCHOLINE IN BRAINS OF RATS OF DIFFERENT AGES

Abstract

Estimations of the acetylcholine (ACh) content of parts of the nervous system of adult albino rats gave the following avg. values in [gamma] of free ACh/g. wet tissue: cerebellum, 0.10; pallium, 0.20; brainstem, 0.58; medulla, 0.37; spinal cord, 1.0; and spinal nerves, 3.4. Young rats (21-26 days): cerebellum, 0.13; pallium, 0.20; brainstem, 0.7; and medulla, 0.8. Infant rats (under 24 hrs. old): cerebellum, 0.26; pallium, 0.16; brainstem, 0.28; and medulla, 0.60. Whole brains of rats gave the following ACh values: adults, 0.47/g., young rats, 0.27/g., and infants, 0.1[gamma]/g. In the discussion an attempt is made to relate the regional distribution of ACh in the mammalian nervous system to other known properties and functions of the parts of this system. Except for the pallium, the changes in ACh level of the parts of the brain, with age, are fairly closely paralleled by changes in respiration, glucose utilization and gly-cogen storage. A close correlation is shown between the distribution of ACh and that of cholinesterase. The parts of the nervous system which are most resistant to anoxia are highest in ACh, while those which are least resistant to anoxia and to hypoglycemia are lowest in ACh.