Acetylcholine is known to increase the contractility of smooth muscle. And norepinephrine is known to decrease the contractility of smooth muscle. Oxytocin is a hormone that causes uterine contractions. Correct?

I did an experiment with a lab rat. We removed the ovaries and then injected the rat with oil and another rat with estrogen. After a week we removed the uterine horns and placed it on a force transducer to record its contractions with acetylcholine added to the uterine horn, then norepinephrine was added and then oxytocin was added. All the results make sense except I'm having trouble with the duration results. In my results ach has decreased, epi has increased and oxytocin has increased. (Which I expected so I have no problem with oxytocin) But why ach and epi? I thought ach would increase the contractions and it would increase over time. I thought epi would decrease because it was known to decrease muscle contractions. I'm really confused.

Can any one help?

Based on the information you provided, it seems that you had conflicting expectations compared to the actual results in your experiment with the lab rat. Let me explain the possible reasons behind these results:

1. Acetylcholine (ACh): You expected ACh to increase the contractions and assumed it would increase over time. However, it appears that ACh decreased in your results. There could be a couple of reasons for this discrepancy. Firstly, it is possible that ACh binds to receptors that may have become desensitized or down-regulated over time, leading to a decrease in the response. Additionally, other factors such as the level of intracellular calcium may influence the contractility of smooth muscle. It's also important to note that the response to ACh can vary depending on the tissue and experimental conditions.

2. Norepinephrine (Epi): You expected norepinephrine to decrease the contractions based on its known effect of decreasing smooth muscle contractility. However, in your results, it increased. This could possibly be due to multiple factors. It is important to consider that the mechanisms underlying the response to norepinephrine can be complex and multifactorial. For example, it is possible that norepinephrine acted on different receptors or signaling pathways that had opposing effects on contractility. Additionally, factors such as receptor density, affinity, and downstream signaling pathways could contribute to the observed response.

Remember that biological systems are intricate and can be influenced by various factors. Interpretation of experimental results requires considering multiple variables and potential interactions. If you're still uncertain about the specific reasons behind your experimental results, it may be beneficial to consult with a research advisor or expert in the field who can provide further insights and guidance.