Aim: Effect of drugs on locomotor activity using Actophotometer
References
- Goodman, L. S., & Gilman, A. (2018). Goodman and Gilman’s The Pharmacological Basis of Therapeutics (13th ed.). McGraw-Hill Education.
- Turner, R. A. (1965). Screening Methods in Pharmacology. Academic Press.
- Kulkarni, S. K. (1999). Handbook of Experimental Pharmacology. Vallabh Prakashan.
Objective
To investigate the central nervous system (CNS) activity—stimulant or depressant—of selected drugs by quantifying locomotor activity in rodents using an actophotometer.
Materials Required
- Laboratory rodents (mice or rats)
- Test drugs (e.g., CNS stimulants like amphetamine, CNS depressants like diazepam)
- Actophotometer (digital or manual)
- Control solution (e.g., sterile saline)
- Stopwatch
- Data recording sheets
- Anesthetic agents (if needed)
- Personal protective equipment (gloves, lab coat, goggles)
Experimental Procedure
1. Animal Preparation: Acclimate animals to the laboratory environment for at least one hour prior to the experiment.Handle animals gently to avoid stress, which can affect behavioral responses.
2. Baseline Locomotor Activity: Place each rodent individually in the actophotometer for a defined period (e.g., 5 minutes).Record the number of beam interruptions, which reflects spontaneous locomotor activity.
3. Drug Administration: Administer the test drug either intraperitoneally or orally based on the protocol.Administer the same volume of saline to the control group.
4. Post-Drug Observations: At set intervals (e.g., 15, 30, 60, 90 minutes post-administration), place each animal back into the actophotometer.Record locomotor activity for a fixed period (e.g., 5 minutes) at each time point.
5. Post-Experiment Monitoring: Observe animals for complete recovery from drug effects.Follow institutional ethical protocols for post-experiment care and housing.
Sample Result Table
(Assuming Diazepam as the test drug)
| Time (minutes) | Locomotor Activity (Beam Interruptions) | Observations |
| Control Group | Test Group | |
| Baseline | 300 | 310 |
| 15 | 295 | 250 |
| 30 | 290 | 200 |
| 60 | 285 | 150 |
| 90 | 280 | 100 |
Discussion
1. Locomotor Activity Changes: A decrease in beam interruptions signifies a reduction in locomotor activity, typically due to CNS depressant action.Conversely, increased beam interruptions indicate CNS stimulation (e.g., by amphetamine).
2. Dose-Response Relationship: Higher doses of CNS depressants cause a progressive decline in activity.CNS stimulants increase activity in a dose-dependent manner until the threshold of toxicity is approached.
3. Behavioral Observations: Note sedation, hyperactivity, stereotypy, grooming, or ataxia depending on the pharmacological profile of the drug.
Precautions
- Adhere strictly to ethical guidelines for the use of laboratory animals.
- Maintain consistent environmental and test conditions.
- Ensure accurate timing and uniform handling to minimize variability.