Strain Differences in Acetylcholine Concentration in the Brain of the Rat

Abstract

WE have recently published results indicating individual and strain differences in cortical and subcortical cholinesterase activity in two strains of rats regularly maintained in the Department of Psychology colony¹. These strains were developed from a heterogeneous foundation stock by Tryon² through selective breeding for maze brightness (the S ₁ strain) and for maze dullness (the S ₃ strain). The brain cholinesterase activity of the S ₁ strain was found to be consistently higher than that of the S ₃ strain. More recently, Roderick³ developed two additional sets of strains of rats differing in cortical and subcortical cholinesterase by a selective breeding programme using the cortical cholinesterase of the sire as the basis of selection. One set was derived from the Dempster and one from the Castle foundation stock of the University of California Genetics Laboratory. Within each set, one strain has a considerably higher brain cholinesterase activity than the other. These four sub-groups are therefore labelled as the RDH (Roderick Dempster High cholinesterase) and RDL, RCH, and RCL strains. We thus have three sets of animals, each deriving from a different foundation stock, and each set further subdivided by selective breeding into strains of high and low brain cholinesterase activity.