BIOASSAY OF d-TUBOCURARINE ::
Rabbit Head-drop Method : Principle ::
d-Tubocararine hydrochloride is injected into the marginal vein of a rabbit s ear till the rabbits neck muscles are relaxed such that the animal cannot hold its head up The total amount of test sample required to produce the endpoint is compared with the total amount of the standard sample required to produce similar endpoint
Selection of Rabbits ::
Rabbits weighing 2 kg are used Animals should be free from disease obtained from a healthy colony and should be accustomed with the experimental procedure
Experimental Procedure ::
Each rabbit is placed in a holder with its head protruding outside The head should be freely movable minimum 8 rabbits are used They are divided into two groups each containing 4 rabbits First group receives standard sample and the second group receives the sample under test d-Tubocurarine solution is injected at a constant speed by infusion apparatus through the marginal vein
First: i.v.inj. of d-tubocuranine Second : Head drop after injection
Injection should be given at a rate of 0.4 ml/min and should take about 10 min Infusion is continued till the rabbit holds its head erect or there will be no response by focussing light on the eyes and the neck gets elongated and toneless
Suitable dose of d-tubocurarine is 0.012% w/v in saline Rabbits recover immediately from the effect of curarization During the expt there is a possibility or respiratory embarrassment which is treated by injecting neostigmine methyl sulphate (0.05 mg) and atropine sulphate immediately through the marginal ear vein
Cross-over test is carried out to minimise biological error due to animal variation Those rabbits which received the standard sample on the first day will be given test sample on the second day of expt and vice versa Mean dose which produces head drop of the test sample is compared with the mean dose of standard preparation
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