We have previously found that the induction of long-term potentiation in the synaptic pathway from the basolateral amygdala to the dentate gyrus (BLA-DG LTP) is regulated by L-type Ca(2+) channels, dopamine D(2) receptors and GABAergic inhibition. In the present study, we investigated possible relations among the three mechanisms by using anesthetized rats. Blockade of GABAergic inhibition with picrotoxin abolished both the inhibitory effect of the dopamine D(2) receptor antagonist chlorpromazine and the promoting effect of the dopamine D(2) receptor agonist quinpirole on the induction of BLA-DG LTP. However, the inhibitory effect of the L-type Ca(2+) channel blocker verapamil on BLA-DG LTP was not affected by picrotoxin. These results suggest that the role of dopamine D(2) receptors in the induction of BLA-DG LTP is modulatory and depends on GABAergic inhibition, whereas the role of L-type Ca(2+) channels is fundamental.