Fig. 7. Central and systemic delivery of buprenorphine decreased brain adenosine concentrations. Microdialysis delivery of buprenorphine to the pontine reticular formation (PnO) oral part (n = 5 rats) or to the substantia innominata (SI) (n = 5 rats) decreased adenosine concentrations in the PnO or SI, respectively (A ). When administered systemically (n = 5), buprenorphine also decreased adenosine concentrations in the SI (B ). Asterisks (*) in A indicate a significant decrease in adenosine concentrations during microdialysis delivery of buprenorphine compared with Ringer's solution (control). Asterisk (*) in B indicates a significant decrease in adenosine concentrations in the SI caused by intravenous (IV) delivery of buprenorphine. Thus, SI adenosine concentrations were decreased by microdialysis delivery of buprenorphine to the SI and by IV buprenorphine (B ).