Adenosine A1 receptor is highly expressed in hippocampus where it inhibits neurotransmitter release and has neuroprotective activity. Similar actions are obtained by increasing cGMP concentration, but a clear link between adenosine A1 receptor and cGMP levels remains to be established. The present work aims to investigate if cGMP formation is modulated by adenosine A1 receptors at the hippocampus and if this effect is gender dependent. cGMP accumulation, induced by phosphodiesterases inhibitors Zaprinast (100μM) and Bay 60-7550 (10μM), and cAMP accumulation, induced by Forskolin (20μM) and Rolipram (50μM), were quantified in rat hippocampal slices using specific enzymatic immunoassays. N6-cyclopentyladenosine (CPA, 100nM) alone failed to modify basal cGMP accumulation. However, the presence of adenosine deaminase (ADA, 2U/ml) unmasked a CPA (0.03–300nM) stimulatory effect on basal cGMP accumulation (EC50: 4.2±1.4nM; Emax: 17±0.9%). ADA influence on CPA activity was specific for cGMP, since inhibition of cAMP accumulation by CPA was not affected by the presence of ADA, though ADA inhibited cAMP accumulation in the absence of CPA. Increasing cGMP accumulation, by about four-fold, with sodium nitroprusside (SNP, 100μM) abolished the CPA (100nM) effect on cGMP accumulation in males but did not modify the effect of CPA in female rats. This effect was reversed by 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX, 100nM), indicating an adenosine A1 receptor mediated effect on cGMP accumulation. In conclusion, adenosine A1 receptors increase intracellular cGMP formation at hippocampus both in males and females under basal conditions, but only in females when cGMP levels are increased by SNP.