Time course of H-reflex conditioning in the rat.
This study sought to define the course of operantly conditioned change in the rat soleus H-reflex and to determine whether, like H-reflex conditioning and spinal stretch reflex conditioning in the monkey, it develops in distinct phases. Data from 33 rats in which the right soleus H-reflex was trained up (i.e. HRup mode) and 38 in which it was trained down (i.e. HRdown mode) were averaged to define the courses of H-reflex increase and decrease. In HRup rats, the H-reflex showed a large phase I increase within the first 2 days followed by gradual phase II increase that continued for weeks. In HRdown rats, the H-reflex appeared to show a small phase I decrease and then showed a gradual phase II decrease over weeks. In combination with other recent work, the data suggest that H-reflex conditioning begins with a rapid mode-appropriate alteration in corticospinal tract influence over the spinal arc of the H-reflex, which causes phase I change, and that the continuation of this altered influence induces gradual spinal cord plasticity that is responsible for phase II change. The results further establish the similarity of H-reflex conditioning in primates and rats. Thus, they encourage efforts to produce a single coherent model of the phenomenon based on data from the two species and indicate the potential clinical relevance of the rat data.
Chen
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Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health and State University of New York, Albany, NY 12201-0509, USA. chenx@wadsworth.org
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Wolpaw
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D000344:Afferent Pathways / Q000166:cytology / Q000502:physiology*; D000818:Animals; D003216:Conditioning, Operant / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology; D013997:Time Factors