Central action of drugs acting on the cholinergic muscarinic receptor. III. Influence of atropine and scopolamine injected intraventricularly on behavior and levels of biogenic amines in the rat brain.

Atropine (At) and scopolamine (Sc) in low doses intensify basic activity, increase amphetamine stereotypy, and suppress catalepsy induced by injection of haloperidol. High doses lower body temperature, antagonize amphetamine stereotypy, and intensify the hypnotic action of chloral hydrate. Doses of about 1/2 LD50 induce narcotic sleep. Both At and Sc in a wide range of dosage protect against the tonic phase of convulsions produced by electroshock. Sc depresses content of acetylcholine in the brain proportionally to its dosage; At had a similar effect only at the lower of the two doses that were used. Both compounds had no effect on levels of noradrenaline and dopamine in the brain. The results indicate that low doses of blockers of the cholinergic muscarinic receptor, injected intraventricularly, produce strong central stimulation, whereas high doses produce depression of the central nervous system.