Metoclopramide gives anti-emetic effect through:
- A- Peripheral action.
- B- Dopaminergic receptor.
- C- Muscarinic receptors.
- D- All of the above.
Metoclopramide's anti-emetic effect is primarily attributed to its B. Dopaminergic receptor action. However, it's not entirely accurate to say it works solely through this mechanism. A more complete answer would be:
C. A combination of Dopaminergic receptor and Muscarinic receptors.
Here's a breakdown of each mechanism:
- Dopaminergic receptors:
Metoclopramide acts as an antagonist at D2 dopamine receptors, particularly in the chemoreceptor trigger zone (CTZ) located in the brain. By blocking these receptors, it inhibits the vomiting reflex triggered by various stimuli. This is the main mechanism of its anti-emetic effect.
- Muscarinic receptors:
Metoclopramide also has weak agonist activity at M1 and M3 muscarinic receptors, which can contribute to its anti-emetic effect by:
- Increasing gastrointestinal motility, which helps move food through the digestive system and prevent nausea and vomiting.
- Stimulating the release of acetylcholine, another neurotransmitter involved in gut motility.
Therefore, while the dopaminergic receptor antagonism plays the primary role, the muscarinic receptor action, though less significant, also contributes to Metoclopramide's anti-emetic effect.
So, the most accurate answer is C. A combination of Dopaminergic receptor and Muscarinic receptors.
