The Plantar Analgesia Instrument represents a remarkable advance in methodology for assessing pain sensitivity in laboratory animals. Unique to the Plantar Analgesia Instrument, the animal is unrestrained and unhandled. This avoids activating the adrenal system, which by itself can affect pain sensitivity and the speed of the animal’s response to pain.

Principle of Operation
Animals move freely (not restrained) on an elevated glass surface. The researcher waits until the animal is at rest, then moves a fiber-optic heat source under the animal’s feet, and triggers the infrared beam. The rising temperature on the bottom of the foot will cause the animal to move its foot. This changes the reflected light which stops the timer. Latency to move the foot is recorded in an automatic (objective) manner.

Major Advantages
Plantar Analgesia testing combines the best features of the other three methods of measuring pain sensitivity.
• It allows bilateral testing, like the Randall-Selitto (paw pressure) method.
• The behavioral end point is detected automatically, as with the Tail Flick method.
• It stimulates the glabrous normal skin of the foot, as opposed to the unique tissue of the tail, as does the Hot Plate method.
• Repeated testing does not result in sensitization, an advantage shared only with the Tail Flick method.

Since the animal is free to move and behave without restraint, other more subjective measures of behavior may also be recorded:
• Duration of the foot lift
• Velocity of the withdrawal reflex
• Associated behaviors such as licking of the paw (Hargreaves, 1988).
These measures, unavailable with any other method of analgesia testing, provide additional information about the effect of the drug and the state of the animal.

Calibration
Each Plantar Test may be accurately calibrated via an I.R. Radiometer (No. 57390) to make sure that its I.R. source delivers the same power flux (expressed in mW per square cm) and hence a nociceptive stimulus of the same intensity.

Data Acquisition
The Plantar Test Apparatus is provided with a connector (D15) for branching it to the 52600 Basile Computer Interface. The data, stored in the 52600 internal memory and shown on its graphic display, can be printed out in real time and/or routed to the computer; in the latter case, the 52010 Win-DAS Software is required.

Complete System
The Plantar Analgesia Instrument comes complete with the sliding infrared source, a glass platform, a base w/ 4 support posts, a three compartment rat enclosure or a six compartment mouse enclosure, a controller, a spare bulb, extra fuses, and a instruction manual. Each of these components is also available separately.