VPT 321: Veterinary Neuropharmacology (2+1)

PROCEDURE

• Definition: Analgesics are agents which relieve pain by raising the pain threshold. They may be classified as narcotic and non-narcotic analgesics Eg: Narcotic analgesics- Morphine, Non-narcotic- Aspirin.
• Aim: To demonstrate the analgesic effect of drugs by applying mechanical (physical) stimulus.

Requisites

• Animals: Mice
• Drugs required: Injection of morphine sulfate / pentazocine
• Instruments: Artery clip with rubber sleeves

Mechanical Stimulus

• Artery clip with rubber sleeves is applied to the base of the tail of a mouse. Due to the pressure of the clip the pain will be induced and the animal will make effort to dislodge the clip. The time taken by the animal to dislodge the clip from the time of application is taken as the end point.
• Six mice are used for this study. The animals are weighed and sex is recorded. To these mice the clip is applied to the base of the tail. The time of application of clip is recorded. The time at which the animal tries to dislodge the clip is recorded. The difference between the two serves as the normal reaction time. To these animals injection morphine / diclofenac / pentazocine is administered at the dose rate of 10mg per kg body weight i.p. Thirty minutes later the same procedure is repeated. If the animal does not respond and try to dislodge the tail clip even after 30 seconds it is considered positive for analgesic effect. The timings are recorded and the reaction time is calculated thereafter. If the reaction time is three times the normal reaction time is considered positive for the analgesic effect and the clip is removed (for example if the normal reaction time is 3 seconds and the reaction time after administration of the drug is 9 seconds it is considered positive).

Results: Date: Dose: Route: Time: Inference

Animal Number	Sex of the animal	Weight of the animal	Time of application of clip	Time at which animal dislodge the clip	Normal Reaction time	Reaction time
						30”	60”	90”	120”	180”
1
2
3
4
5
6