title: Altered thermal responsiveness during regeneration of corneal cold fibers.
abstract: 1. To date, there has been no quantitative, systematic, study of the electrophysiology of regenerating cold receptors. This study, therefore, examines the changes in cold-receptor neural activity following a circular wound (5 mm dia, 200 microns deep) on the surface of the rabbit cornea. This is a well studied wounding model, in which neural regeneration has been anatomically quantified. 2. Extracellular recordings were obtained from a total of 90 single cold fibers, at 1, 3, 10, 20, or 30 days following wounding. The adapting temperature was 35 degrees C in all experiments. Thermal sensitivity for each fiber was determined by using a series of temperature steps, 0.2 degree C ranging from 35 to 34 degrees C, and 2 degrees C steps ranging from 35 to 24 degrees C. The rate of temperature change ranged from 0.2 to 1 degree C/s. 3. At the adapting temperature, the tonic activity of the regenerating cold-fibers was not significantly different from normals. Conduction velocities for regenerating cold-fibers were slower on day 1 postwounding compared with normal fibers, 0.59 +/- 0.04 and 0.75 +/- 0.04 (SE) M/s, respectively, however, were within the normal range by day 30 postwounding, 0.72 +/- 0.06 M/s. 4. On day 1, sprouting fibers showed decreased responsiveness to cooling (P < 0.05). At days 3 and 10 postwounding, action potential rates in response to cooling were enhanced by 180-200% of normal (P < 0.05) and returned to preinjury values by 20 to 30 days postwounding.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, Dallas 75235-9068, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Tanelian
authors.forename: S
authors.initials: S
authors.lastname: Monroe
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001369:Axons / Q000502:physiology; D003080:Cold Temperature; D003315:Cornea / Q000294:innervation / Q000502:physiology*; D004594:Electrophysiology; D005110:Extracellular Space / Q000502:physiology; D006358:Hot Temperature; D066298:In Vitro Techniques; D009412:Nerve Fibers / Q000502:physiology*; D009416:Nerve Regeneration / Q000502:physiology*; D010812:Physical Stimulation; D011817:Rabbits; D011984:Sensory Receptor Cells / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D013268:Stimulation, Chemical; D014794:Visual Fields / Q000502:physiology