Abstract
The effects of carbachol and phenylephrine on circular and longitudinal muscle from the fundus of the rabbit stomach have been studied. Carbachol (2 × 10‐8 ‐ 5 × 10‐5 M) produced an increase in tone in all the strips. The maximum response in the circular strips was approximately 4 times greater than that in the longitudinal strips. The response to phenylephrine depended on the existing tone of the muscle when the drug was added: In inactive strips, phenylephrine (2 × 10‐7 ‐ 10‐4 M) always increased the tone. In moderately contracted (10‐7 M carbachol) longitudinal strips, the response was biphasic – a transient relaxation preceded a sustained contraction – while in the circular strips it was purely excitatory. In strongly contracted (5 × 10‐7 ‐ 2 × 10‐6 M carbachol) strips, phenylephrine caused a small transient relaxation, irrespective of whether the strips were cut circularly or longitudinally. The results emphasize the importance of defining the existing tone when responses to catecholamines are studied.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call