Dopaminergic D1/D5-receptor-mediated processes are important for certain forms of memory and its cellular model, i.e. hippocampal long-term potentiation (LTP) in CA1. D1/D5-receptor function is required for the induction of the protein synthesis-dependent maintenance of CA1-LTP (late-LTP) by activating the cAMP/PKA-pathway. In earlier studies we had reported a synergistic interaction of D1/D5-receptor function and N-methyl-D-aspartate (NMDA)-receptors (Frey, 2001, Long-lasting hippocampal plasticity: cellular model for memory consolidation? In: Richter, D. (Ed.), Cell Polarity and Subcellular RNA Localization. Springer-Verlag, Berlin-Heidelberg, pp. 27-40). Interestingly, the short-term application of D1/D5-receptor agonists (SKF38393 or 6-bromo-APB, 50 microM) can induce a slow-onset potentiation. This D1/D5-agonist-induced delayed-onset potentiation (D1/D5-LTP) resembles late-LTP, i.e. it is dependent on protein synthesis in the CA1 of rat hippocampal slices in vitro. The question arises as to whether D1/D5-LTP also requires glutamatergic stimulation, i.e. NMDA-receptor activation. We provide first evidence that a synergistic role of D1/D5- as well as NMDA-receptor-function is required in mediating processes relevant for the maintenance of this protein synthesis-dependent potentiation.