Tail-Flick Test
Overview
The tail-flick test measures spinal nociceptive reflex latency by applying a focused radiant heat source (or hot water immersion) to the tail and recording the time until the animal reflexively flicks its tail away from the stimulus. This is a spinal reflex mediated by the S1–S4 dorsal horn segments and does not require supraspinal processing, making it a clean measure of spinal nociceptive transmission and a complement to supraspinal assays like the hot plate.
The radiant heat variant (D'Amour-Smith method) focuses an infrared beam on a defined point on the tail (typically 2–3 cm from the tip), providing precise and reproducible stimulation. The tail-flick test is particularly sensitive to opioid analgesics and is used extensively for determining antinociceptive potency (AD50), constructing dose-response curves, and studying opioid tolerance and dependence at the spinal level.
ConductMaze integrates with the radiant heat source to control beam intensity, detect tail movement via photocell sensor, and automatically record flick latency. The software enforces cutoff times (typically 10 s) to prevent tissue damage, supports repeated measurements at multiple tail positions, and calculates %MPE for group comparisons and dose-response analysis.
Trial Flow
Restrain Animal
Gently restrain animal; position tail on heat source groove
Heat Application
Activate radiant heat beam on tail (2–3 cm from tip)
Detect Flick
Photocell detects tail displacement from beam path
Record Latency
Log time from heat onset to tail flick
Cutoff Check
Stop heat if cutoff (10 s) reached; assign cutoff value
End
Allow 5 min inter-trial interval; repeat if needed
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Heat intensity | arbitrary | 55 | Radiant heat beam intensity (calibrated to give 3–5 s baseline) |
| Cutoff time | seconds | 10 | Maximum heat exposure to prevent tissue damage |
| Tail position | cm | 2–3 | Distance from tail tip to heat application point |
| Number of trials | integer | 3 | Trials per timepoint (averaged for threshold) |
| Inter-trial interval | minutes | 5 | Minimum rest between consecutive trials |
Metrics
| Metric | Unit | Description |
|---|---|---|
| Flick latency | seconds | Time from heat onset to tail withdrawal |
| %MPE | % | Percent maximum possible effect for analgesic studies |
| AD50 | mg/kg | Dose producing 50% antinociception in tail-flick (from dose-response) |
| Baseline latency | seconds | Pre-drug tail-flick latency (should be 3–5 s) |
| Tolerance index | ratio | Shift in AD50 after repeated drug administration |
Sample Data
| Subject | Group | Dose (mg/kg) | Baseline (s) | Post-Drug (s) | %MPE |
|---|
Representative data for illustration purposes. Actual values will vary by species, strain, and experimental conditions.
Applications
- 1Opioid potency ranking — spinal AD50 determination for mu, kappa, and delta agonists
- 2Spinal analgesia — intrathecal drug delivery studies targeting dorsal horn receptors
- 3Tolerance and dependence — chronic opioid dosing and dose-response curve rightward shifts
- 4Descending modulation — PAG stimulation or lesion effects on spinal reflex threshold
- 5Spinal cord injury — below-level nociceptive reflex changes after contusion or transection
Related Protocols
Compatible Products
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