Adenosine is a neuromodulator that controls neurotransmitter release through inhibitory A₁ and facilitatory A_2A receptors. Although both adenosine receptor-mediated inhibition and facilitation of glutamate release have been observed, it is not clear whether both A₁ and A_2A receptors are located in the same glutamatergic nerve terminal or whether they are located on different populations of these terminals. Thus, we have tested if single pyramidal glutamatergic neurons from the hippocampus simultaneously expressed A₁ and A_2A receptor mRNA and if A₁ and A_2A receptors were co-localized in hippocampal glutamatergic nerve terminals. Single cell PCR analysis of visually identified pyramidal neurons revealed the simultaneous presence of A₁ and A_2A receptor mRNA in four out 16 pyramidal cells possessing glutamatergic markers but not GABAergic or astrocytic markers. Also, A₁ and A_2A receptor immunoreactivities were co-localized in 26±4% of nerve terminals labeled with antibodies against vesicular glutamate transporters type 1 or 2, i.e. glutamatergic nerve terminals. This indicates that glutamatergic neurons in the hippocampus co-express A₁ and A_2A receptors and that these two receptors are co-localized in a subset of glutamatergic nerve terminals.