Which of the following is the mechanism of action of tetanospasmin –
**Core Concept**
Tetanospasmin is the neurotoxin responsible for the clinical manifestations of tetanus. It is a potent inhibitor of inhibitory neurotransmission, specifically targeting glycine and GABA receptors in the central nervous system.
**Why the Correct Answer is Right**
Tetanospasmin binds to the glycine receptor, a chloride channel, and blocks its activity, leading to an increase in excitatory neurotransmission. This results in muscle rigidity, spasms, and hyperreflexia. The toxin also affects the GABA receptor, further contributing to the development of tetanic spasms. The mechanism of action of tetanospasmin is closely related to its potent effect on the glycine receptor.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as tetanospasmin does not act by increasing the release of acetylcholine, which is involved in the transmission of nerve impulses at the neuromuscular junction.
**Option B:** This option is incorrect as tetanospasmin does not act by stimulating the release of dopamine, which is a neurotransmitter involved in the regulation of movement and reward.
**Option C:** This option is incorrect as tetanospasmin does not act by inhibiting the enzyme acetylcholinesterase, which is responsible for the breakdown of acetylcholine in the synaptic cleft.
**Clinical Pearl / High-Yield Fact**
Tetanus is a clinical condition characterized by muscle rigidity, spasms, and hyperreflexia, which can be life-threatening if not treated promptly. The tetanus toxin is highly potent and requires only a small dose to produce severe clinical manifestations.
**Correct Answer: C. Inhibition of glycine receptor.**