AIM:

To examine the antagonism of tacrine on the amnesic effects of scopolamine (Sco), anisodine (AT3), atropine (Atr), and anisodamine (Ani).

METHODS:

Cognitive functions and locomotor activities were determined using two sessions of step-through and open-field tests, respectively. Mice were injected with one of the belladonna alkaloids (0.05-50 mumol.kg-1, i.p.) and tacrine (50 mumol.kg-1, s.c.) 30 min before the first session.

RESULTS:

Tacrine completely blocked the avoidance-learning deficit caused by Sco 0.5 mumol.kg-1, AT3 and Atr 5 mumol.kg-1, or Ani 50 mumol.kg-1. But tacrine partly antagonized the learning deficit induced by Sco 5-50 mumol.kg-1 or Atr and AT3 50 mumol.kg-1. The avoidance-memory deficit caused by Sco 0.05-5 mumol.kg-1 or Atr 5 mumol.kg-1 was completely or partly attenuated by tacrine, which did not antagonize the memory deficit elicited by Sco and Atr 50 mumol.kg-1, AT3 5 and 50 mumol.kg-1, and Ani 50 mumol.kg-1. During the acquisition, the locomotor activity of the mice was inhibited by tacrine. This reduction was completely antagonized by Sco 0.5-50 mumol.kg-1, AT3 5-50 mumol.kg-1, Atr 5-50 mumol.kg-1, and only partly antagonized by AT3 and Atr 0.5 mumol.kg-1 or Ani 50 mumol.kg-1.

CONCLUSION:

Compared with the avoidance-memory deficit, the avoidance-learning deficit caused by belladonna alkaloids is more preferentially attenuated by tacrine.