Modulatory role of dopamine D2 receptors and fundamental role of L-type Ca2+ channels in the induction of long-term potentiation in the basolateral amygdala-dentate gyrus pathway of anesthetized rats

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 Ca2+ channels, dopamine D2 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 D2 receptor antagonist chlorpromazine and the promoting effect of the dopamine D2 receptor agonist quinpirole on the induction of BLA-DG LTP. However, the inhibitory effect of the L-type Ca2+ channel blocker verapamil on BLA-DG LTP was not affected by picrotoxin. These results suggest that the role of dopamine D2 receptors in the induction of BLA-DG LTP is modulatory and depends on GABAergic inhibition, whereas the role of L-type Ca2+ channels is fundamental.