Pain reactivity of monkeys after lesions to the dorsal and lateral columns of the spinal cord

Summary Macaca speciosa monkeys were trained to escape electrical stimulation of either hindlimb, and they were given the alternative of witholding the response for 10 sec to receive food reward. The force, latency and threshold of escape responses were measured as a function of stimulation intensity before and after lesions of the spinal cord. The stimulus range was set so that pain was certainly evoked by some portion of the intensities above escape threshold, and it was inferred that pain reactivity was altered if the force or latency curves or both were shifted by a lesion. Ipsilateral dorsal column lesions decreased pain reactivity as revealed by higher latencies and lower forces of escape responses. Thresholds were generally unaffected. Ipsilateral lesions of the dorsolateral column produced hyperesthesia, or reduced latencies and increased forces. Thresholds were again unaffected. Contralateral lesions of the lateral column elevated thresholds, and this effect was magnified by inclusion of the dorsal columns in the lesion.Supported by Grant NS07261 from the National Institute of Neurological Diseases and Stroke, U.S. Department of Health, Education and Welfare, Bethesda, Maryland, and the Veterans Administration Hospital, Gainesville, Florida. The research described in this report involved animals maintained in animal care facilities fully accredited by the American Association for Accreditation of Laboratory Animal Care. The animal care was provided in part by N.I.H. grant FR00421. We thank Dorothy Robinson for technical assistance.During this investigation, Dr. Hamilton was supported by a postdoctoral fellowship from the Center for Neurobiological Sciences (grant MH10320 from the National Institutes of Mental Health).