Peripheral neural transmission: NANC transmission

Question 1

Caffeine

Answer 1

A1 receptor antagonist
Waking action most potent after prolonged wakefulness

Non-selective, also inhibits PDE - therefore potentiates cAMP mediated signalling, increases rate & force of cardiac contraction

Question 2

Dypyridamole

Answer 2

Blocks transport of Adenosine into cells (thus blocks inactivation of adenosine)
Potentiates responses mediated by endogenous adenosine.

Question 3

Glyceryl trinitrate

Answer 3

Nitrovasodilator, aka nitric oxide donor

Produces vasodilatation & relaxation of smooth muscle

Question 4

Isosorbide dinitrate

Answer 4

Nitrovasodilator, aka nitric oxide donor

Produces vasodilatation & relaxation of smooth muscle

Question 5

7-NI

Answer 5

Selectively inhibits NOS in neurones (appears to act selectively on the cell type rather than the isoenzyme)
Does not affect eNOS or iNOS in their cells.

Question 6

L-NIO

Answer 6

Potent & reversible inhibitor of iNOS in activated macrophages

Question 7

Asymmetric dimethylarginine (ADMA)

Answer 7

Endogenous inhibitor of NOS
Approximately equipotent with the synthetic L-NMMA
Synthesized during post-translational protein methylation.

• [ ] increased in hypercholesteraemia- could contribute to endothelial dysfunction in CVD.
• Plasma AMDA elevated in renal failure. Clinical trials in patients with chronic kidney disease show that [AMDA] is a marker of the severity of the disease & a predictor of the progression of renal dysfunction.

NB inhibition of NOS might not be the basis of this correlation- raised levels of the symmetric isomer SDMA (not a NOS inhibitor) also negatively correlate with survival rates.