To study the local anaesthetic activity of lignocaine hydrochloride on rabbit cornea (surface anaesthesia method)

Principle

Local anaesthesia is the condition that results when sensory input from a local area to the CNS is blocked. Local anaesthetics are drug which reversibly block conduction of impuses along the nerve axons and excitable membrane.

Equipment required

1) Stopwatch

2) Rabbit cages to keep rabbits in place

3) Dropper

4) Camel hair

Animal required

Albino rabbits.

Albino Rabbit 

Drug solution required

Lignocaine hydrochloride (0.1%, 0.2%, 0.4%, 0.5%, 1% and 2%)

Procedure

1) Select 6 healthy albino rabbits weighing about 1.5 to 2 kg body weight.

2) Trim their eye lashes one day before the experiment.

3) Keep each rabbit separately in a rabbit cage and number the cage.

4) Instill the lowest concentration of the lignocaine hydrochloride solution on the corneal surface of the rabbit, so that the space between eyelids contained a clearly visible film of the solution. Note the time of administration of drug solution.

5) Stimulate the cornea by touching it with a camel hair a minute after instillation.

6) Stimulate the cornea at 60 seconds interval for a period of 30 minutes.

7) Count the number of times animal fails to respond to a corneal stimuli during 30 minutes period.

8) Find out the onset of action, duration of action and degree of anaesthesia.

Observation and conclusion

Local application of lignocaine hydrochloride solution produces loss of sensation at the site of application. The above observation indicates that lignocaine hydrochloride is a surface anesthetic agent.