A dopamine receptor agonist such as bromocriptine (Parlodel) relieves muscle rigidity caused by antipsychotic medication by:

Correct Answer: D. Activating dopamine receptors in the CNS

Extrapyramidal effects and the muscle rigidity induced by antipsychotic medications are caused by a low level of dopamine. In groups of patients with Parkinson’s disease where levodopa is no longer as effective, co-administration with dopamine agonists such as bromocriptine historically was a successful option. Further, bromocriptine is also used as an early treatment for PD to delay the onset of the use of levodopa, ultimately delaying the likely dyskinesia and motor fluctuations that occur with chronic use.

• Option A: Dopamine receptor agonists stimulate dopamine receptors and thereby reduce rigidity. Bromocriptine is a dopamine receptor agonist that has selective agonist activity on D2 dopamine receptors while simultaneously acting as a partial antagonist for D1 dopamine receptors.[12] Dopamine agonism has variable effects depending on the target tissue. In Parkinson disease, bromocriptine binds directly to striatal dopamine D2 receptors, stimulating locomotion and attenuating the bradykinetic symptoms caused by the degeneration of dopaminergic nigrostriatal neurons.
• Option B: Parkinson disease (PD) is a progressive neurological disorder characterized by resting tremor, rigidity, akinesia or bradykinesia, and postural instability due to the loss of dopaminergic neurons in the substantia nigra. Although levodopa is an effective treatment of PD, with chronic use, there is a decline in efficacy and motor complications.
• Option C: They don’t affect norepinephrine or acetylcholine. Bromocriptine is a medication currently used in the management and treatment of Type II diabetes mellitus. It is an ergot alkaloid derivative in the dopamine D2 agonist class of drugs. This discussion reviews the indications, contraindications, and mechanism of action for bromocriptine as a valuable agent in the management for Type II diabetes mellitus, as well as its more traditional uses in Parkinson’s disease, acromegaly, and pituitary prolactinomas.