False statement regarding Lithium is
**Core Concept**
Lithium is a mood stabilizer used in the management of bipolar disorder. It works by inhibiting the reuptake of serotonin and norepinephrine, thus increasing their availability in the synaptic cleft. Lithium also has a stabilizing effect on the neuronal membranes and inhibits the release of catecholamines.
**Why the Correct Answer is Right**
Lithium's mechanism of action is complex and involves multiple pathways. It inhibits the enzyme inositol monophosphatase, which is involved in the phosphatidylinositol signaling pathway. This leads to a decrease in the synthesis of inositol, a crucial component of phosphatidylinositol, and ultimately results in a decrease in the activity of the protein kinase C (PKC) enzyme. PKC is involved in the release of neurotransmitters, including serotonin and norepinephrine. By inhibiting PKC, lithium reduces the release of these neurotransmitters, leading to a decrease in mood swings and manic episodes.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because lithium does not primarily work by increasing the synthesis of serotonin and norepinephrine. While it does have some effect on these neurotransmitters, its primary mechanism of action is through the inhibition of inositol monophosphatase and subsequent decrease in PKC activity.
**Option B:** Incorrect because lithium does not primarily work by blocking the reuptake of serotonin and norepinephrine. While it does have some effect on these neurotransmitters, its primary mechanism of action is through the inhibition of inositol monophosphatase and subsequent decrease in PKC activity.
**Option C:** Incorrect because lithium does not primarily work by increasing the release of catecholamines. While it does have some effect on catecholamines, its primary mechanism of action is through the inhibition of inositol monophosphatase and subsequent decrease in PKC activity.
**Option D:** Incorrect because the statement is not entirely false. Lithium does have a stabilizing effect on the neuronal membranes, but this is not its primary mechanism of action.
**Clinical Pearl / High-Yield Fact**
Lithium has a narrow therapeutic index, and its levels must be closely monitored to avoid toxicity. The therapeutic range for lithium is typically between 0.6 and 1.2 mmol/L, and levels above 1.5 mmol/L can lead to toxicity.
**Correct Answer: C.**