RESUMO
It is a well-established fact that adenosine and its receptor subtypes [A 1 and A 2] are involved in changes of contractility, heart rate and coronary blood flow [CBF] under different circumstances. This study was conducted to evaluate the role of nitric oxide and prostaglandins in development of these changes. For this purpose, Nitro-L-Arginine methyl ester [L-NAME], and indomethacin as inhibitors of nitric oxide and prostaglandins synthesis were used respectively. In this respect, guinea pig isolated hearts were randomly divided into control [receiving adenosine] and groups II and III which received L-NAME [100 micro M] and indomethacin [50 nM] before adenosine application, respectively, using isolated heart setup. The results showed that adenosine increased CBF and decreased heart rate and contractility in control group. In the presence of L-NAME, adenosine was less effective in enhancing the CBF and decreasing cardiac contractility. Furthermore, no significant change was observed in the presence of indomethacin [regarding all of parameters]. It can be concluded that nitric oxide [and not prostaglandins] is essential for the effect of adenosine on CBF and cardiac contractility