. A 27-year-old woman experiences reduced visual acuity and color vision in her left eye. This is
accompanied by general facial weakness, numbness, and dysarthria. The symptoms resolve fully
within 24 hours. Three months later she begins experiencing muscle spasticity, balance problems,
and the urge to run to the bathroom. She undergoes an MRI which reveals white matter lesions in
her brain and spinal cord. An agent with which of the following mechanisms of action might be
effective in treating her spasticity?
- A) Muscarinic agonist
- B) Muscarinic antagonist
- C) Nicotinic agonist
- D) Nicotinic antagonist
- E) GABA-A agonist
- F) GABA-A antagonist
- G) GABA-B agonist
- H) GABA-B antagonist
- I) Glutamate agonist
- J) Glutamate antagonist
- K) Mu-opioid agonist
- L) Kappa-opioid agonist
0 voters
The answer is G.
This patient has relapsing-remitting multiple sclerosis.
Optic neuritis and urge incontinence, as seen in this patient, are common presenting features.1
MRI is the gold standard for diagnosis.2 CNS white matter lesions are characterized by multifocal
areas of myelin sheath destruction, oligodendrocyte death, axonal and neuronal damage, and
activation of glial cells.3
NKG2C-expressing CD4 T cells are present in white matter lesions and kill human
oligodendrocytes.4
Baclofen, a GABAB receptor agonist, is used to treat spasticity in multiple sclerosis.5, 6
This drug might sound weird and low-yield, but the USMLE really likes it. And they want you to
know that it agonizes, not antagonizes, GABA B, not A