“…In addition, the adenosine A 1 receptor selective antagonist DPCPX, blocked the inhibitory effect of a NO donor and zaprinast on hippocampal synaptic transmission (Broome et al, 1994), suggesting an involvement of adenosine A 1 receptor. Later, it was shown that both NO donor and zaprinast increase the release of adenosine -an effect not mediated by cGMP -a finding explaining the adenosine A 1 receptor-dependent inhibitory action of NO donors and zaprinast on neurotransmission (Arrigoni and Rosenberg, 2006). An indirect evidence of adenosine A 1 receptor action on cGMP levels at the nervous system came from a recent study, where the inhibitory effect of peripheral adenosine A 1 receptor on inflammatory hypernociception was blocked by sGC and PKG inhibitors, suggesting a cGMP-mediated effect of the adenosine A 1 receptor (Lima et al, 2010); however a direct effect of adenosine A 1 receptor on cGMP levels was not evaluated.…”