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Previous reports have described increases in the size and number of cholinergic neurons in the basal forebrain in p75 neurotrophin receptor (p75^NTR) knockout mice. In an earlier study, we also found improved spatial memory in these mice, raising the possibility that p75^NTR regulates hippocampal function by its effects on the cholinergic basal forebrain. We therefore investigated hippocampal long‐term potentiation in p75^NTR knockout mice that shared the same genetic background as control 129/Sv mice. We also investigated heterozygous mice, carrying just one functional p75^NTR allele. The p75^NTR knockout mice had enhanced long‐term potentiation in the Schafer collateral fiber synapses of the hippocampus. Heterozygous mice had an intermediate level, greater than controls but less than knockout mice. Hippocampal choline acetyltransferase activity was also markedly elevated in p75^NTR knockout …