Selective impairments to memory consolidation in chicks produced by 5'-iodo-2'-deoxyuridine.

The aim of the present work was to study the role of DNA synthesis in the formation of different types of memory in neonatal chicks. The nucleotide analogs 5'-iodo-2'-deoxyuridine (IdU) and 5'-bromo-2'-deoxyuridine (BrdU) were used; these are incorporated into DNA, impairing its function, and have amnestic actions in defined models of learning in mice. We studied the effects of 5'-iodo-2'-deoxyuridine of the formation of long-term memory in chicks during training in different models: passive avoidance, imprinting, taste aversion, and spatial learning in a maze. In the taste aversion model, i.p. administration of IdU (10 mg/kg 5 min before or 50 min after training) had an amnestic effect on testing 1-2 days after training. IdU-induced amnesia developed more than 6 h after training, while administration of IdU 2 h after training had no amnestic effect. 5'-Bromo-2'-deoxyuridine also had a similar amnestic action in the taste aversion model. In the passive avoidance, imprinting, and spatial maze learning models, administration of IdU at the same dose before and after training did not induce amnesia. These data lead to the suggestion that DNA synthesis in the brain may play a critical role in the mechanisms of memory consolidation in chicks in types of learning such as taste aversion.