The activity of acetylcholinesterase (AChE), adenylate cyclase (AC), 5'-nucleotidase (NT), Na+, K(+)-ATPase, as well as the contents of phospholipids (PL) and gangliosides (G) per mg of protein in homogenate, crude membrane (P2) fraction, and synaptosomes from the sensorimotor cortex of the right and left hemispheres of rat brain were analyzed under normal and hypoxic conditions. The authors found that under normal physiological conditions there are no significant differences of the studied parameters in homogenates of sensorimotor cortex from the right and left hemispheres. In P2 fractions, and especially in preparations of synaptosomes from the right and left cortex, differences in the activity of 5'-NT and AC were found. Hypoxia (pO2 = 7.8%) was shown to alter studied parameters (AChE, AC, Na+, K(+)-ATPase activity, and PL content) mainly in the right hemisphere.