Activation of dopamine D1 receptors enhances long-term depression of synaptic transmission induced by low frequency stimulation in rat hippocampal CA1 neurons

The effects of both activation and blockade of dopamine (DA) D1 receptors on long-term depression (LTD) of synaptic transmission were examined in CA1 neurons of rat hippocampal slices. Low frequency stimulation (LFS) consisting of 450 pulses at 1 Hz induced LTD (−14.3%, mean, n = 10) in the slope of the field excitatory postsynaptic potential. SKF-38393 (3–10 μM), an agonist of DA D1 receptors, significantly enhanced LFS-induced LTD (−31.1%, n = 11). SCH-23390 (2 μM), an antagonist of DA D1 receptors, blocked the induction of LTD by LFS (2.5%, n = 6). These results indicate that DA D1 receptors play an important role in the modulation of LFS-induced LTD in rat hippocampal CA1 neurons.