[Effect of arecoline on the structure of rest and active wakefulness in the catfish Ictalurus nebulosus].

The investigation demonstrated, that in the representative of the Osteichthyes--Ictalurus nebulosus, the hematoencephalic barrier for quaternary ammonium compounds is strongly pronounced. The difference in ability of tertiary and quaternary cholinergic substances to penetrate from the blood into the brain of this fish can be used for study of the presence and functional role of cholinoreceptive brain neurons. The pharmacological analysis showed the presence of cholinoreceptive neurons in the fish brain, participating in the activity of the functional systems which generate the "swimming automatism"--rhythmic movements of the tail, that are not accompanied by progression of the body. Apparently, this "swimming automatism" is the element of the future paradoxical sleep, which appears in its complete form in birds and mammals.