VPT 321: Veterinary Neuropharmacology (2+1) copy 1

PROCEDURE 

Objective

To study the onset and duration of intravenous anaesthetics in rats

Principle

• Intrvenous anaesthetics induce general anaesthesia by CNS depression. Their potency and efficacy are compared by observing the different reflexes and the onset and duration of general anaesthesia.
  • Animal : Rat
  • Apparatus required: Dental syringe with hypodermic needle
  • Drug: Thiopental sodium, distilled water

Procedure

• The rats are weighed, numbered and the sex of the animal noted. Respiratory rate and heart rate are recorded.
• A 2.5% solution of thiopental sodium is made by dissolving 0.5 G of thiopental sodium in 20 ml of distilled water. The dose of the drug required for each rat is 40 mg/kg body weight. Accordingly the dose for each rat under experimentation is calculated and the calculated dose of the drug is taken in a dental syringe and injected intra peritoneally and the time when the drug is administered is noted (A).
• The animal is observed and its respiratory and the heart rate are recorded. When the animal goes into its lateral recumbency. The time the animal goes to its lateral recumbency is recorded as (B).
• After placing the animal on the table the corneal and pedal reflexes are checked at regular intervals. The time when the animal loses its pedal reflex is recorded as (C). The heart rate and respiratory rate are also recorded during the period.
• The pedal reflex is gained thereafter and the time at which the animal regains its pedal reflex is recorded as (D).
• The animal is observed for regaining of sternal recumbency and the time when the animal regains its sternal recmbency is recorded as (E).
• By this way different stages of anaesthesia i.e., Stage 1,stage2,stage3 and stage4 of anaesthesia may be observed chronologically.
• The animal is placed in the cage after the experiment. The same procedure is repeated with the other rats.