Zx. Chen et al., ROLES OF DOPAMINE-RECEPTORS IN LONG-TERM DEPRESSION - ENHANCEMENT VIAD1 RECEPTORS AND INHIBITION VIA D2 RECEPTORS, Receptors & channels, 4(1), 1996, pp. 1-8
The effects of both the activation and the blockade of D1 or D2 dopami
ne receptors on long-term depression (LTD) of synaptic transmission, a
nd the involvement of NMDA and GABA receptors in LTD, were investigate
d in CA1 neurons of rat hippocampal slices. Low-frequency stimulation
(LFS, 450 pulses at 1 Hz) produced LTD of the slope of field EPSPs (-1
4.3%, mean, n = 10). The induction of LTD was blocked by the NMDA rece
ptor antagonist, AP5 (1.4%, n = 7), by the D1 receptor antagonist, SCH
-23390 (3.5%, n = 8), or by the D2 receptor agonist, LY-171555 (4.4%,
n = 8). Either the activation of D1 receptors by SKF-38393 or the bloc
kade of D2 receptors by sulpiride produced significantly larger LTD th
an the control LTD (-31.1%, n = 11; -30.6%, n = 9, respectively). Alth
ough LTD was blocked by picrotoxin, a GABA(A) receptor/Cl- channel ant
agonist (4.9%, n = 8), LTD was produced by LFS in the medium containin
g both SKF-38393 and picrotoxin (-27.3%, n = 7). These results indicat
e that: (1) the induction of LTD by LFS in hippocampal CA1 neurons is
under the influence of both NMDA and GABA receptors; (2) both D1 and D
2 receptors are involved in the modulation of LTD in that the activati
on of D1 receptors enhances LTD, while that of D2 receptors inhibits L
TD, and (3) while the induction of LTD is blocked by picrotoxin, this
effect is superseded by SKF-38393.