The possible involvement of brain microtubules in memory fixation.

Goldfish were trained to discriminate between two coloured lights. When colchicine was administered intracranially immediately after training it produced complete retrograde amnesia 2 days later, but the fish displayed considerable retention if instead the injection was given 1-25 h after training. If colchicine was administered 1-25 h before training the fish were able to learn as readily as control fish but then showed retrograde amnesia when tested 2 days later. It is suggested that colchicine may affect memory fixation by interfering with the fast transport of material needed to bring about a structural modification at certain synapses.