The effect of administration of SM 21 on memory processes was evaluated in
the mouse passive avoidance and in the rat social learning tests. SM 21 (10
-20 mg kg(-1) i.p.) prevented amnesia induced by scopolamine and dicyclomin
e as tested by the mouse passive avoidance test and prevented memory disrup
tion by AF-64A and benehexol ascertained by the rat passive avoidance test.
Both SM 21 enantiomers were able to abolish dicyclomine-induced amnesia in
mice. SM 21, starting from the dose of 10 mg kg(-1) i.p., antagonized the
memory impairment produced by mecamylamine, baclofen, and diphenhydramine i
n mice, as well as amnesia induced by diazepam in rats. SM 21, at doses ran
ging between 10 and 30 mg kg(-1) i.p., prevented memo reduction in mice by
hypoxia in the passive avoidance test. In the social learning test, SM 21 (
10 mg kg p.) injected in adult rats reduced the duration of active explorat
ion of a familiar partner in the second session of the test. SM 21 prevente
d amnesia in both mice and rats comparable to that of the cholinesterase in
hibitor physostigmine (0.2 mg kg(-1) i.p.), the M-1 selective agonist AF-10
2B (10 mg kg(-1) i.p.), and the nootropic drug piracetam (30 mg kg(-1) i.p.
). These results demonstrated the ability of SM 21 to modulate memory funct
ions and suggests that SM 21 could be useful in the treatment of cognitive
deficits. (C) 1999 Wiley-Liss, Inc.