Weight gain caused by antipsychotics is due to antagonism of :
**Core Concept**
Weight gain associated with antipsychotic medications is a complex phenomenon involving multiple factors, including alterations in appetite regulation, metabolism, and energy balance. The primary mechanism underlying this effect is related to the antagonism of specific receptors involved in the regulation of appetite and energy homeostasis.
**Why the Correct Answer is Right**
Antipsychotic-induced weight gain is primarily attributed to the blockade of **dopamine D2 receptors** in the hypothalamus, a key brain region regulating appetite and energy balance. This blockade disrupts the normal dopaminergic signaling, leading to an increase in appetite and food intake, thereby contributing to weight gain. Additionally, some antipsychotics also exhibit **serotonin receptor antagonism**, particularly at the 5-HT2C receptor, which can further modulate appetite and weight regulation.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specifically relate to the primary mechanism of antipsychotic-induced weight gain. While other receptors may be involved, the dopamine D2 receptor antagonism is the key factor.
**Option B:** This option is incorrect as it refers to a different class of medications, which are not directly associated with the weight gain effects of antipsychotics.
**Option C:** This option is incorrect as it is a partial explanation, but not the primary mechanism underlying antipsychotic-induced weight gain.
**Clinical Pearl / High-Yield Fact**
A mnemonic to remember the key receptors involved in antipsychotic-induced weight gain is "DAD": Dopamine D2 and Serotonin (5-HT2C) antagonism.
**Correct Answer:** C.