Principle of d-Tubocurarine
d-Tubocurarine is a non-depolarizing neuromuscular blocker that prevents acetylcholine from activating nicotinic receptors at the neuromuscular junction.
The bioassay measures loss of muscle contraction (e.g., twitch response) in response to nerve stimulation.
Methods
Frog Rectus Abdominis or Chick Biventer Cervicis Assay (In Vitro)
Procedure:
Mount the muscle in an organ bath, stimulate it electrically.
Record the twitch height with standard d-tubocurarine added at increasing doses, then wash and repeat with test sample.
Potency Determination: Compare the concentration needed to reduce the twitch by 50% (EC50) for standard vs. test.
Mammalian (e.g., Rat) Nerve-Muscle Preparation (In Vivo)
Procedure:
Anesthetize rat, stimulate the sciatic nerve, measure the twitch response of the gastrocnemius muscle.
Administer standard and test preparations of d-tubocurarine in incremental doses, noting the blockade of muscle twitch.
Potency Determination: Compare dose-response blockade curves.