The Plantar Test (Hargreaves’ Method) enables the researcher to discern a peripherally mediated response to thermal stimulation caused by drugs in the unrestrained rat.
The system consists of:
• A movable infrared source
• A glass pane onto which the rat enclosure is located
• A controller
A rat is placed into one of the three compartments. After an acclimation period, the infrared source is placed under the glass floor and is positioned by the operator directly beneath the hind paw. A trial is commenced by depressing a key which turns on the infrared source and starts a digital solid state timer.
When the rat feels pain it will withdraw its paw. The withdrawal of the paw causes a sudden drop in the reflected radiation which switches off the infrared source and stops the reaction time counter. The withdrawal latency is calculated to the nearest 0.1 second. The 3-compartment enclosure has been provided to speed up the test when a number of animals are involved. In each compartment the animal is unrestrained.
The Heat-Flux Infrared Radiometer 37300 has been designed to calibrate infrared sources, in particular the Plantar Test.
Calibration Radiometer
Each plantar test is accurately calibrated via an infrared radiometer to make sure that its infrared source delivers the same power flux (expressed in mW per square cm) and hence a nociceptive stimulus of the same intensity.
The end user should consider the Heat-Flow Infrared Radiometer Model an extremely useful accessory. This Infrared Radiometer is a battery operated, self sufficient instrument complete with infrared probe, digital meter and adaptors for the Tail Flick and Plantar Test. All parts are neatly lodged in a sturdy plastic case with punched
foam lining.
This Radiometer enables the experimenter to:
i) Check (and adjust if necessary) the I.R. emission. In fact, the I.R. output of the Plantar Test may in the course of
one-two years undergo to 2-3% reduction, due to dust gathered on the optics, blackening of the I.R. bulb, accidental knocks, ageing of components due to thermal cycles, etc.
Moreover, in case the bulb is replaced or the electronics serviced, output alteration of more significant magnitude, say, 8-10%, may take place.
ii) Make sure that two or more Plantar-Test units deliver
thermal nociceptive stimuli of exactly the same intensity. Balance them, if necessary.
iii) Know the I.R. energy (1 mW for the duration of 1s
corresponds to 1 mJ) in absolute terms, a useful datum to compare with any equal or different method/instrument described in the literature
Data Acquisition
The Plantar Test is provided with a connector (D15) for branching it to the 6-Channel Multi-Function Printer or the 48-Channel Multi-Function Printer, see page G11. Both Multi-Function Printers are microprocessor controlled devices, designed to acquire data from either 6 or 48 independent channels. Each Plantar Test requires 1 channel. The data is stored in the internal memory and is shown on its graphic display. The data may also be printed real time or may be exported to a PC computer. The data export to a PC requires the purchase of the Win-DAS Software Package, see accessories. This must be purchased as a separate product.
The data, stored in the 2600/2650 internal memory and shown on its graphic display, can be printed out in real time and/or routed to the PC; in the latter case, the 2010 Win-DAS Software Package is required.
The Plantar Test System includes:
Controller, Emitter/Detector Vessel, complete with cable, Platform with supporting columns, Framed Glass Pane, Three-Compartment Rat Enclosure, Spare Bulb, Mains Cable, Instruction Manual, 1.5 mm Allen Wrench, Dust Cover, and Set of Fuses for 230 V operation or 115 V operation. Bibliography Methods Paper:
• K.M. Hargreaves, R. Dubner, F. Brown, C. Flores and J. Joris: “A New and Sensitive Method for Measuring Thermal Nociception in Cutaneous Hyperalgesia.” Pain 32: 77-88, 1988.
Additional Papers:
• K.M. Hargreaves, R. Dubner and J. Joris: “Peripheral Action of Opiates in the Blockade of Carrageenan-Induced Inflammation” Pain Research and Clinical Management. Vol. 3. Elsevier Science Publishers, Amsterdam: 55-60, 1988
• G. Benneth and Y.K. Xie: “A Peripheral Neuropathy in Rat that Produces Disorders of Pain Sensation Like Those Seen in Man” Pain 33: 87-107, 1988.
• M. Iadarola and G. Draisci: “Elevation of Spinal Cord Dynorphin mRNA Compared to Dorsal Root Ganglion Peptide mRNAs During Peripheral Inflammation” In: The Arthritic Rat as a Model of Clinical Pain? by J. Besson and G. Guilbaud (eds.) Elsevier Press, Amsterdam: 173-183, 1988.
• A. Costello and K.M. Hargreaves: “Suppression of Carrageenan-Induced Hyperalgesia. Edema and Hyperthermia by a Bradykinin Antagonist” European J. Pharmacol., 1989.
• K.M. Hargreaves, R. Dubner and A. Costello: “Corticotropin Releasing Factor (CRF) has a Peripheral Site of Action for Antinociception” European J. Pharmacol., 1989.
• J. Hylden, R. Nahin, R. Traub and R. Dubner: “Expansion of Receptive Fields of Spinal Lamina I Protection Neurons in Rats with Unilateral Adjuvant-Induced Inflamma-tion: The Contribution of Central Dorsal Horn Mechanisms” Pain 37: 229-244, 1989.