MS-2292

A 35-year-old woman arrives at the emergency department with lock-jaw and muscle spasms throughout her body, particularly in the abdomen and back. She reports cutting her hand on a rusty knife covered in soil while gardening a week ago.

During the examination, the patient displays trismus, an arched back, and visible distress. The palm of her hand shows a four-inch cut with redness, warmth, and pus.

Which neurotransmitter is involved in the pathophysiology of the probable diagnosis?