Medial frontal cortex lesions selectively attenuate the hot plate response: possible nocifensive apraxia in the rat

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Abstract
Formalin, hot-plate, and tail-flick tests. Average hot-plate latencies, but not formalin test scores or tail-flick latencies, were significantly increased by an average of 82% in rats with medial frontal cortex lesions, as compared to sham-operated control rats. Motor function, as tested by righting and foot lifting responses and clinical observation, was not impaired. No effects were seen on hot-plate latencies, tail-flick latencies, and formalin pain scores in sham-operated rats. These results suggest that the medial frontal cortex of the rat mediates certain types of supraspinally organized responses to noxious heat pain. Lesions that include the medial frontal and anterior cingulate cortex appear to disrupt the integration of increasing heat nociceptive input with motor responses that are necessary to execute quickly the escape behavior in the hot-plate test. *Corresponding author. Kenneth L. Casey, M.D., Veterans Affairs Medical Center, Neurology 127, 2215 Fuller Road, Ann Arbor, MI 48105, USA. Tel.: (313) 761-7956. (Received 6 September 1994; revised version received 3 March 1995; accepted 13 March 1995.) © Lippincott-Raven Publishers....