EVIDENCE THAT THE TAIL-FLICK RESPONSE IS SPINALLY MEDIATED IN RATS IRRESPECTIVE OF TEST TEMPERATURE. T.E. KING*, M. PAYNE, & J. W. GRAU. Department of Psychology, Texas A & M University, College Station, TX 77843.
Researchers frequently test pain reactivity in rodents by measuring the latency at which subjects withdraw their tail from a radiant heat source (the "tail-flick test"). It is commonly held that this response is spinally mediated when the heat source is intense, but depends on supraspinal mechanisms when intensity is decreased (Jensen & Yaksh, 1986). Contrary to this claim, we report that the tail-flick response is spinally mediated over a wide range of test conditions.
Rats (N=16) were tested a day after they experienced either a spinal transection (at T2) or a sham operation. Testing was conducted with a radiant heat tail-flick device while subjects were loosely restrained in tubes. Each subject was tested at 4 different intensities, the order of which was counter-balanced using a latin square design. At each intensity, the subjects received 3 tail-flick tests at 2 m intervals. The mean tail-flick latencies (±SE) observed in sham operated rats were: 3.50 (±.35), 4.47 (±.48), 5.71 (±.43), and 9.92 (±.74) (from hottest to coolest). Similar values were obtained from spinalized subjects: 3.77 (±.52), 5.32 (±.87), 6.91 (±.56), and 11.07 (±.98). An ANOVA confirmed that changing the heat intensity had a significant impact (p < 0001). Neither the main effect of operation (p > .20), nor its interaction with heat intensity (p > .76), approached statistical significance. Supported by MH48994 to J.W.G.
Published in Society for Neuroscience Abstracts, 19, 1993, 965.