Does nitric oxide modulate transmitter release at the mammalian neuromuscular junction?

1. Application of the nitric oxide (NO) donor, sodium nitrite and the NO synthase substrate l-arginine had no effect on nerve-evoked transmitter release in the rat isolated phrenic nerve/hemidiaphragm preparation; however, when adenosine A(1) receptors were blocked with the adenosine A(1) receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) prior to application of sodium nitrate or l-arginine, a significant increase in transmitter release was observed. In addition, the NO donor s-nitroso-N-acetylpenicillamine (SNAP) significantly increased transmitter release in the presence of DPCPX.

Effect of theophylline and aminophylline on transmitter release at the mammalian neuromuscular junction is not mediated by cAMP.

1. Theophylline and aminophylline have been widely used as inhibitors of phosphodiesterase when examining the role of cAMP in regulating cell function. In reality, however, these phosphodiesterase inhibitors may have additional sites of action that could complicate the interpretation of the results.