title: Nature of the late potentials and F-ratio values in dogs.
abstract: There is controversy about the nature of the late potentials (F-waves and H-reflexes) in dogs. This work has attempted to clarify the problem by comparing late potentials in eight intact and four chronically deafferented dogs. Pure H-reflexes were recorded inconsistently from intact preparations at voltages below the threshold for the M-wave. At stimulation voltages giving maximum direct responses, there was no statistically significant difference between the amplitude and latency of the late potentials of the two groups. However, there was a tendency for the late potentials to be of larger amplitude and longer duration in intact preparations. Late potentials in intact preparations had a composite waveform consisting of both F-waves and H-reflex components. F-waves only were present in deafferented limbs, and their amplitude was proportional to the intensity of the stimulus. F-ratios could be calculated by using the latencies of the late potentials, because the F-wave did not have a longer latency than the H-reflex. The following reference values for the F-ratio are proposed: 1.954 +/- 0.086 when stimulating at the hock and 0.883 +/- 0.052 when stimulating at the popliteal fossa.
authors.affiliation: Department of Small Animal Surgery, Faculty of Veterinary Medicine, University of Liège, Brussels, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Poncelet
authors.forename: M
authors.initials: M
authors.lastname: Balligand
mesh_terms: D000818:Animals; D004285:Dogs / Q000502:physiology*; D004558:Electric Stimulation; D004566:Electrodes / Q000662:veterinary; D004576:Electromyography / Q000662:veterinary; D005071:Evoked Potentials; D005121:Extremities; D005260:Female; D008297:Male; D009132:Muscles / Q000294:innervation / Q000502:physiology*