Vasomotor reversal of Dale is due to:
**Core Concept**
Vasomotor reversal of Dale refers to the phenomenon where a drug that initially causes vasoconstriction (narrowing of blood vessels) eventually leads to vasodilation (widening of blood vessels). This reversal occurs due to the depletion of the neurotransmitter or hormone responsible for the initial vasoconstrictive response.
**Why the Correct Answer is Right**
The correct answer is related to the depletion of a neurotransmitter that causes vasoconstriction. Dale's vasomotor reversal is a classic example of the depletion of a neurotransmitter leading to a paradoxical effect. In this case, the neurotransmitter is likely to be norepinephrine (noradrenaline), which is released from the nerve terminals and causes vasoconstriction. However, the continuous release of norepinephrine leads to its depletion, resulting in the release of vasodilatory substances, such as acetylcholine, which causes vasodilation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not provide a clear explanation for the vasomotor reversal phenomenon.
* **Option B:** This option is incorrect because it does not mention the depletion of a neurotransmitter, which is the key factor in Dale's vasomotor reversal.
* **Option C:** This option is incorrect because it is too vague and does not provide a clear explanation for the phenomenon.
**Clinical Pearl / High-Yield Fact**
Dale's vasomotor reversal is a classic example of the biphasic response of the body to a stimulus, where an initial response is followed by a paradoxical response due to the depletion of the neurotransmitter responsible for the initial response.
**Correct Answer: C.