D1/D5 RECEPTOR AGONISTS INDUCE A PROTEIN SYNTHESIS-DEPENDENT LATE POTENTIATION IN THE CA1 REGION OF THE HIPPOCAMPUS

Agonists of the dopamine D1/D5 receptors that are positively coupled to adenylyl cyclase specifically induce a slowly developing long-lasting potentiation of the field excitatory postsynaptic potential in the CA1 region of the hippocampus that lasts for >6 hr. This potentiation is blocked by the specific D1/D5 receptor antagonist SCH 23390 and is occluded bg the potentiation induced by cAMP agonists. An agonist of the D2 receptor, which is negatively coupled to adenylyl cyclase through G(alpha i), did not induce potentiation, Although this slow D1/D5 agonist-induced potentiation is partially independent of N-methyl-D-aspartate receptors, it seems to share some steps with and is occluded by the late phase of long-term potentiation (LTP) produced by three repeated trains of nerve stimuli applied to the Schaffer collateral pathway. Similarly, the D1/D5 antagonist SCH 23390 attenuates the late phase of the LTP induced by repeated trains, and the D1/D5 agonist-induced potentiation is blocked by the protein synthesis inhibitor anisomycin. These results suggest that the D1/D5 receptor mag be involved in the late, protein synthesis-dependent component of LTP in the hippocampal CA1 region, either as an ancillary component or as a mediator directly contributing to the late phase,