<prompt> Dantrolene acts on ?Raynodine receptorCannabinoid receptorBoth of the aboveNone of the above  <response>: 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 Ca2 - 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. 