Why did curare affect motor nerves but not sensory nerves in Claude Bernard’s experiments?

In his experiments, Claude Bernard demonstrated that curare causes paralysis by specifically blocking the transmission of impulses between motor nerves and muscles at the neuromuscular junction.12

Curare does not affect sensory nerves because its mechanism of action is limited to the site of chemical communication between nerve fibers and muscle cells. Specifically, the drug acts as a competitive antagonist that binds to acetylcholine receptors on the muscle fiber membrane. By competing with acetylcholine—the neurotransmitter responsible for stimulating muscle contraction—curare prevents the nerve impulse from successfully activating the skeletal muscle. Because sensory nerves do not rely on this specific neuromuscular junction mechanism to transmit signals, they remain unaffected by the drug. Bernard’s work was pivotal in distinguishing between neuromuscular transmission and primary muscular or nerve conduction mechanisms.321