Pro-cognitive activity induced in the rat by low doses of R-(+)-hyoscyamine.

In the passive-avoidance test R-q.-hyoscyamine 10]100 mg kgy1 i.p.. prevented amnesia induced by antimuscarinic treatment with AF-64A and benzhexol. The antiamnesic effect of R-q.-hyoscyamine was comparable to that exerted by the cholinesterase inhibitor physostigmine 0.2 mg kgy1 i.p. and the M1 selective agonist AF-102B 10 mg kgy1 i.p... In the social learning test, R-q.-hyoscyamine 10]100 mg kgy1 i.p.. in adults rats, reduced the duration of active exploration of the familiar partner in the second session of the test similar to the nootropic drug piracetam 30 mg kgy1 i.p... These results demonstrated the ability of R-q.-hyoscyamine to modulate memory functions and suggest that R-q.-hyoscyamine could be useful in the treatment of cognitive deficits