ABSTRACT
This chapter aims to summarize the effects of narcotic analgesics, psychotomimetics, barbiturates, and stimulants on isolated enzymes and enzyme systems. The first demonstrable effects of a narcotic analgesic directly on an enzyme or enzyme system were reported by F. Bernheim and M. L. C. Bernheim in 1936. These investigators found that the addition of morphine to crude brain homogenates containing cholinesterase inhibited the hydrolysis of acetylcholine to choline and acetic acid. Even though the buildup of acetylcholine at the synapse has been interpreted as resulting from the inhibition of transmitter release, other mechanisms may be equally possible. Barbiturates like phenobarbital also increase the acetylcholine level in cerebral tissue. Much attention has been paid to the inhibition of various cholinesterases by lysergic acid dethylamide (LSD). A few investigators have reported an activating effect of LSD on the cholinesterases derived from human serum and rat brain.
