Synaptic proteins of the temporal associative area of the neocortex of cats (field Ep) with normal and reduced cognitive capacities.

The upper, middle, and lower subfractions of the synaptic membranes and subfractions of the total synaptoplasm were isolated from fractions of light and heavy synaptosomes of the Ep fields of the cat brain. The content of protein and protein sulfhydryl (SH-) groups was determined spectrophotometrically in the subsynaptic fractions. The maximal content of the reactive SH-groups was detected in the upper membrane subfractions; this characterizes the structure of the membranes of cholinergic synapses that are primarily concentrated in them, and the minimal content was detected in the lower subfractions, primarily noncholinergic. The brain of cats with well-developed and low capacities for the solution of problems involving generalization, gnosis, and abstraction was compared. A substantially lower content of protein in the upper and middle subfractions of the light synaptosomes and an increased reactivity of SH-groups in the membrane-bound proteins of the upper and middle subfractions of the light and heavy synaptosomes were found in animals with well-developed cognitive capacities. The hypothesis that the synaptic architectonics of the Ep fields in cats with strong cognitive capacities are distinguished by an increased relative proportion of the cholinergic structures is discussed.