[Studies on the effect of urapidil on the central nervous system and various organ functions in animal experiments (author's transl)].

Compared to the changes in spontaneous behaviour of mice and rats, 6-(3-[4-(o-methoxyphenyl)-1-piperazinyl]-propyl-amino)-1,3-dimethyluracil (urapidil, Ebrantil) in doses from 10 mg/kg p.o. has a central sedative action, for which it is typical that it can be interrupted by external stimuli after doses of up to approx. 100 mg/kg. By this action urapidil differs from other central-acting drugs, e.g. chlor-promazine, diazepam and clonidine. It can be assumed that urapidil has no central dopamine blocking qualities because it does neither influence the conditioned avoidance response nor the amphetamine-induced gnawing of the rat. Urapidil is also different from diazepam bacause it does not hinder spinal polysynaptic motor reflexes of the decerebrated cat. Up to 80 mg/kg p.o. of urapidil, there was no hypotensive effect in the rat to be seen and, therefore, it can be concluded that changes in spontaneous and reactive behaviour are not due to acute changes in cardiovascular functions. The antihistamine effect of urapidil in the isolated ileum of the guinea pig is approx. 15 times weaker than that of chlorpromazine, furthermore urapidil has no anticholinergic quality.