Figure 4.

Treatment with a D1/D5 agonist in the presence of a novel holeboard elicits slow-onset depression. Learning-facilitated LTD is unaffected. (A) SC-CA1 synaptic strength was not significantly altered following holeboard exploration in the absence of test-pulse stimulation. In contrast, holeboard exploration in the absence of test-pulse stimulation but in the presence of a selective D1/D5 agonist (42 μg of chloro-PB), resulted in slow-onset depression lasting >4 h. Insets: Analog traces represent SC-CA1 field potentials during baseline, 15 min, and 4 h after holeboard exploration. Calibration: vertical bar, 1 mV; horizontal bar, 3 ms. (B) LFS of SCs (LFS, 1 Hz, 600 pulses) resulted in STD that lasted for approximately 2 h. When LFS was given concurrently with novel exploration of the object-containing holeboard, STD was facilitated into LTD that lasted for over 24 h. Application of the D1/D5 agonist (chloro-PB, 42 μg, n = 8) had no effect on the profile of learning-facilitated LTD elicited.