Dantrolene acts on ?
Raynodine receptor
Cannabinoid receptor
Both of the above
None of the above
Ans. is 'a' i.e., Raynodine receptor Dantrolene Dantrolene is a directly acting skeletal muscle relaxant. Mechanism of action Normally excitation (depolarization of end plate) is coupled with contraction by Ca" Excitation contraction coupling. Dantrolone acts on Ryanodine receptors (RyR) Calcium channels in sarcoplasmic reticulum of skeletal muscles and prevents their depolarization triggered opening - no release of intracellular Ca+2 - No excitation contraction coupling - No contraction. That means muscle contraction is uncoupled from depolarization of the membrane. Dantrolene is DOC for malignant hypehermia. It can also be used in Neuroleptic malignant syndrome. To reduce spasticity in UMN disorders, hemiplegia, paraplegia, cerebral palsy and multiple sclerosis. Muscular weakness is the dose limiting side effect. Other side effects are sedation, malaise, light headedness, troublesome diarrhoea and liver toxicity. Remember Quinine also acts as directly acting muscle relaxant. It increases refractory period and decreases excitability of motor end plates. It can be used in nocturnal leg cramp.