cAMP/PKA and β-adrenergic signaling pathways upstream of TrkB are dysregulated in I/R and diabetic I/R group. (A) ADRB2 mRNA expression in MI and MI + DM rats based on online microarray profile (GSE12639). (B) ADRB2 mRNA expression in rat hearts (n=5) from Sham, DM, I/R, or I/R + DM group determined by real-time PCR. (C) The concentration of cAMP in rat hearts from Sham, DM, I/R, or I/R +DM group determined by ELISA. (D, E) The protein levels of ADRB2, p-PKA, and PKA in rat hearts from Sham, DM. I/R, or I/R + DM group determined by Immunoblotting, n=3. **P<0.01, compared to sham group; #P<0.05, ##P<0.01, compared to DM group; && P<0.01, compared to I/R group.