Dopaminergic D1/D5-receptor blokade within the nucleus accumbens and its effect on hipocampal long-term potentation in the dentate gyrus of freely mooving animals
Hippocampal long-term potentiation (LTP) is considered to be a cellular model of learning and memory. It has been shown that stimulation of modulatory brain regions can infl uence hippocampal LTP. Quite little is known of the role played by the nucleus accumbens (NAc) on hippocampal LTP. The NAc is the central component of the basal ganglia positioned to integrate signals arising from corticolimbic areas and to translate them into motor behavior. Electrical stimulation of the NAc core and shell region has been shown to modulate LTP in the dentate gyrus. We were now interested to study if the dopaminergic system within the NAc affects LTP in the dentate gyrus in freely moving animals. Thus, we have applied a specifi c dopaminergic D1/D5-receptor blocker, SCH23390, into the NAc and studied its possible effect on control potentials as well as on LTP in the dentate gyrus in freely moving rats. Interstingly, treated animals show a depression in baseline responses recorded in the dentate gyrus, just by D1/D5-blockade within the NAc. Furthermore, these animals were characterized by a reduced LTP after weak tetanic stimulation of the perforant path when compared with controls. As there is no direct dopaminergic connection between NAc and dentate gyrus, the effects must involve indirect mechanisms, such as glutamatergic and/or GABAergic pathways.