THE DORSAL NORADRENERGIC BUNDLE MODULATES DNA REMODELING IN THE RAT-BRAIN UPON EXPOSURE TO A SPATIAL NOVELTY

A series of experiments were designed to study the role of the dorsal noradrenergic bundle (DNB) in the modulation of genomic remodeling in the mammalian brain. A series of experiments were designed to study th e role of the dorsal noradrenergic system in relation to nonassociativ e tasks. Adult male Sprague-Dawley rats were either bilaterally lesion ed in the DNB by intrabundle microinjection of B-hydroxydopamine or we re sham lesioned. All rats were given 50 mu Ci [H-3-methyl]-thymidine and were sacrificed 0.5 h later. After the injection of the tracer, ra ts were either left undisturbed in the home cage or were exposed to a Lat-maze for 15 min after 15 min had passed from the time of injection , During the exposure to the maze, corner crossings and rearings were monitored. The rate of DNA synthesis was determined in several brain r egions by measuring the amount of tracer incorporated into the DNA ove r a 0.5-h duration pulse. Under baseline conditions DNB-lesioned rats showed an increase in DNA synthesis in the hippocampus, hypothalamus, and rest of the brain. On the other hand, following exposure to the La t-maze, sham-lesioned rats only showed an increase in DNA synthesis in the hippocampus, as compared to baseline conditions. Conversely, DNB- lesioned rats did not show an increase in hippocampal DNA synthesis as in the sham-lesioned rats. In contrast, DNA synthesis was increased i n the neocortex and rest of the brain. In conclusion, the data support a role for noradrenergic systems in modulating brain DNA synthesis, p robably of the unscheduled type, during information processing and sto rage.