Dopaminergic modulation of oscillatory network inhibition in the rat basolateral amygdala depends on initial activity state.

The amygdala receives dopaminergic innervation, and dopamine (DA) enhances various activities in cognitive and emotional behaviors. Periodic bursts of spontaneous inhibitory postsynaptic currents (IPSCs) with a low (<1 Hz) inter-event frequency have been observed in projection neurons of the basolateral nucleus of the amygdala (BL). Blockade of ionotropic glutamate receptors or GABA(A) receptors abolishes these oscillatory IPSC bursts in the BL, suggesting that the activity has a network origin. Here, we investigated dopaminergic modulation of the oscillatory network inhibition in rat brain slices. We evaluated the effects of DA receptor agonists and antagonists on the network inhibition; the resultant changes were quantified by integrated power spectral density (0.1-3.0 Hz). DA enhanced the power when its initial activity was low, but reduced it when the activity was initially robust. These changes in the power were accompanied by changes in burst IPSC amplitude. D1-like receptor agonist SKF 38393, or DA together with the D2-like receptor antagonist sulpiride, reproduced DA's facilitatory actions. D2-like receptor agonist quinpirole did not change the periodic IPSC burst activity of the high baseline power, though D(4) receptor agonist PD 168077, or DA together with the D1-like receptor antagonist SCH 23390, reduced its activity. These results suggest that: 1) dopaminergic modulation of the oscillatory network inhibition depends on its initial activity; and 2) facilitatory and suppressing effects of DA in the BL are mediated by D1-like receptors and D(4) receptors, respectively.