Tetanus toxin primarily affects which neurotransmitter release?

Tetanus toxin primarily affects the release of GABA, which is an inhibitory neurotransmitter in the central nervous system. When tetanus toxin enters the body, it retrogradely transports within motor neurons and inhibits the release of inhibitory neurotransmitters, particularly GABA and glycine. This disruption leads to increased muscle tone and spasms due to the unopposed action of excitatory neurotransmitters, resulting in the characteristic muscle stiffness and spasms seen in tetanus.

It is important to note that while the other neurotransmitters listed have significant roles in neuronal communication, they are not primarily affected by tetanus toxin. Acetylcholine, for instance, is critical in muscle contraction but does not play a direct role in the mechanism of action of tetanus toxin, which specifically targets inhibitory signaling. Understanding the role of GABA in regulating muscle relaxation highlights why the inhibition caused by tetanus toxin leads to severe clinical symptoms.