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Suggestions on experiments?

daemon at net.bio.net daemon at net.bio.net
Wed Apr 14 15:46:26 EST 1999

Dear Colleagues:

I'm doing experiments about relaxing effects of carbon monoxide (CO) on
the guinea pig ileal longitudinal muscle.  Our hypothesis is that one of
the action mechanisms of CO is an inhibition of voltage dependent Ca
channel (we previously confirmed this inhibition through voltage clamp
technique).  We are now going to do the experiment about CO's effect on
the tension of the guinea pig ileal longitudinal muscle.

To clarify the Ca channel involvement in this relaxing action, the
blocking effects of some Ca channel antagonists on the CO's relaxing
action would be necessary.  So we tried to do that experiment (as

First of all, we applied carbachol (or acetylcholine) or high K (40mM,
or 25mM) solution and recorded the initial transient and subsequent
tonic contraction, and could observe that CO inhibited this tonic
contraction significantly.  Then we tried to test the effects of some
organic Ca channel antagonists (verapamil) on the CO's relaxing action. 
However, when we applied Ca channel antagonists (not so high dose)
during the tonic contraction, the contraction was almost completely
suppressed, therefore, we could not evoke further relaxation with CO
solution (as you know, I think ... , in that experimental condition,
definite demonstration" or "expression" of the Ca channel involvement
would be impossible .... I think, to demonstrate the Ca channel
involvement in CO's relaxing action, some measurable portion of the
contraction should be maintained [or preserved] even after applying the
Ca channel antagonists).

Eventually, "I'd like to demonstrate the involvement of Ca channel in
CO's relaxing action by using of a tension measurement."  

Regarding my dilemma above mentioned, can anyone give me some tips or
more useful experimental protocols for demonstrating the Ca channel
involvement using a tension measurement?  Any suggestion would be
greatly appreciated.

Thanks in advance.

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