Basolateral amygdala D1- and D2-dopaminergic system promotes the formation of long-term potentiation in the dentate gyrus of anesthetized rats

We have previously found that the induction of hippocampal long-term potentiation (LTP) is modulated by neuron activities in the basolateral amygdala (BLA). However, little is known about what neurotransmitter system in the BLA contributes to modulation of hippocampal LTP. In the present study, we investigated possible involvement of BLA dopaminergic system in the induction of LTP at the perforant path (PP)–dentate gyrus (DG) granule cell synapses of anesthetized rats. The induction of PP–DG LTP was significantly attenuated by intra-BLA injection of the D1 receptor antagonist SCH23390 (2 or 6 nmol) or the D2 receptor antagonists, chlorpromazine (30 or 100 nmol) or haloperidol (4.4 or 13.3 nmol). The effects of SCH23390 and haloperidol were abolished by concomitant intra-BLA injection of the D1 receptor agonist SKF38393 (17 nmol) and the D2 receptor agonist quinpirole (3 nmol), respectively. Furthermore, lesioning with 6-hydroxydopamine of the ventral tegmental area, the origin of the dopaminergic system projecting to the BLA, resulted in attenuated PP–DG LTP, which was restored by intra-BLA injection of SKF38393 or quipirole. These results suggest that the induction of PP–DG LTP is promoted by the BLA dopaminergic system via both D1 and D2 receptors.