Effect of Acetylcholine on Intestinal Smooth Muscle Contraction
A segment of isolated rabbit ileum was suspended in an organ bath of tyrodes solution and connected to a kymograph. Rhythmic phasic contractions were recorded.
Acetylcholine was added to the organ bath and caused an immediate very large increase in tone. Following this the amplitude of contractions was approx. 90% smaller than amplitude observed prior to ACh addition – tone gradually started to decrease with time. Contraction amplitude gradually started to increase.
Is the initial large increase in tone caused by a sudden large increse in intracellular calcium levels (caused by extra ACH)
Why is amplitude of contractions so small to begin with and why does tone remain so high (rate seems to be unaffected)? – I don’t fully understand why amplitude of contractions is so small initially and also why the rate of contraction isn’t affected.
Thanks for your help