A relatively small proportion of synapses are potentiated in individual CA1 pyramidal neurones following conventional long-term potentiation (LTP) stimulating protocols. This makes it difficult to detect changes in the amplitudes of mEPSCs which would indicate that changes in synaptic efficacy are mediated, in part, by alterations in the numbers of AMPA receptors. Thus, to mimic the LTP-like postsynaptic calcium concentration change that occurs following NMDA receptor activation, we have used a depolarising voltage pulse (VP) stimulating protocol to increase intracellular calcium levels via L-type calcium channels. Neonatal rats (postnatal day 7-10) were killed by decapitation, with Home Office authority, and hippocampal slices were prepared for organotypic cell culture. In whole-cell patch-clamp recordings from CA1 neurones in slices cultured for 7-14 days we observed that mean mEPSC amplitudes increased from 21.2 ± 1.6 pA to 45.1 ± 2.2 pA, following VP stimulation (n = 25; mean ± SEM; P0.05). To assess whether the increase in amplitude of mEPSCs requires the insertion of AMPA receptors into postsynaptic sites we inhibited the actions of several proteins involved in intracellular membrane fusion events. In all experiments, inhibitors were included in the patch-pipette to restrict their actions to the postsynaptic cell. We observed that both N-ethylmaleimide (5 mM, n=6) and botulinum toxin A (10 ng/ml, n=7) blocked the induction of VP potentiation while interleaved control experiments showed typical potentiation. Pep2m (50 μM), a peptide that blocks the NSF binding site on the C-terminus of the GluR2 AMPA receptor subunit (Nishimune et al. 1998), similarly blocked VP potentiation, while a scrambled version of this peptide, Pep4c (50 μM), failed to block potentiation (control mEPSC amplitude 22.9 ± 1.6 pA, n=5; Pep2m 24.2 ± 1.6 pA, n=8; Pep4c 48.3 ± 4.5 pA, n=8). Next we examined the effects of Pep-AVKI (50 μM) to explore the possible involvement of PICK-1 in VP potentiation. This peptide also blocked potentiation (control 17.1 ± 1.2 pA; Pep-AVKI 19.5 ± 2.4 pA, n=8). None of the peptides examined altered mean mEPSC amplitude (or frequency) in recordings where they were included in the patch-pipette but no voltage-pulses were applied. We conclude that VP potentiation shares common expression mechanisms with NMDA receptor-dependent LTP. The VP protocol provides a valuable method for studying biochemical changes in individual neurones following changes in synaptic strength.