Study of local anesthetics by Spinal anaesthesia in rats

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Local anaesthesia is a technique to create loss of sensation in specific region of the body.1 Usually they are used in minor surgeries, dental procedures, cesarean section with reduced pain and distress. This technique is safer and superior to general anaesthesia.2

Local anaesthetic drugs produce reversible effect and a loss of nociception. When these drugs are used on specific nerve pathways they show effects such as analgesia and paralysis. Local anaesthetics differ in their pharmacological properties and are used in various techniques such as surface (topical) anaesthesia, infiltration, epidural block, plexus block and spinal anaesthesia.2

The aim of the present study is to determine the activity and tolerability of new local anaesthetics after intrathecal injection in albino rats.


Animals required:
Male Sprague-Dawley rats of weight 50-75 g are used.

Lignocaine 0.2%, test drug (0.05% and 0.1%). Drugs should be dissolved either in saline or in water.

Instruments used:
25 µl syringe (30 guage needle)


Select male rats for the study. Firmly hold the rat by the pelvic girdle. Insert Hamilton syringe with needle into the tissue on one side of L5-L6 spinous process at an angle 20o. Slowly process the needle to the groove between spinous and transverse processes and then move to the intervertebral space at an angle of about 100. About 0.5 cm of the needle should be there in the vertebral column. Arching of the tail indicates correct placement of the needle. Then give the drug to the animal at a dose of 5 µl. Evaluate the effect of anaesthesia by using antinocipetion activity by tail flick assay by placing rats tail under radiant heat source. Do the test before and after 30, 60, 90 and 120 minutes of drug administration.



Reaction time in seconds after drug administration

30 min

60 min

90 min

120 min

Lignocaine (2%)

Test drug (0.05%)

Test drug (0.1%)


Time between placing the tail of rat on radiant heat source and its with drawl from heat source was called as reaction time. This reaction time will determine the effects of anaesthesia.


  1. William A, Catterall A, Kenneth M. Local Anesthetics. In: Laurence Bruton L,Goodman and Gilmans The Pharmacological Basis of Therapeutics, 12 th ed. New Delhi: Mc Graw Hill Medical; 2011: 564.
  2. Local anesthesia. Available at: Accessed on 17 October 2017.
  3. Vogel GH. Spinal anaesthesia in rats. Drug Discovery and evaluation-Pharmacological assays. 2nd edition. Newyork: Springer-Verlag; 2002: 658-559.