Identification and characterization of afferent periodontal C fibres in the cat.
The presence of afferent periodontal C fibres was studied in pentobarbitone-anaesthetized cats. Extracellular single-fibre recordings were made from fine nerve filaments split from the proximally cut end of the inferior alveolar nerve. Periodontal nerve fibres were identified by constant-current stimulus pulses applied via platinum wire electrodes inserted into the periodontal space. Of 260 periodontal nerve fibres, 142 (55%) were classified as C fibres according to their conduction velocities (less than or equal to 2.5 m/sec) as determined by electrical stimulation of the periodontal ligament (c.v.p). The mean (+/- S.D.) c.v.p was 1.2 +/- 0.6 m/sec (n = 142; range: 0.3-2.5 m/sec). In addition, the axonal conduction velocity of 14 periodontal C fibres was determined by bipolar electrical stimulation of the trunk of the inferior alveolar nerve (c.v.n). On average the c.v.n was 42% higher than the c.v.p; the mean value was 1.7 +/- 0.8 m/sec (n = 14; range: 0.6-3.9 m/sec). Nevertheless, the classification of nerve fibres based on c.v.p proved to be reliable; only 1 fibre had a c.v.p less than 2.5 m/sec and a c.v.n greater than 2.5 m/sec and a c.v.n greater than 2.5 m/sec and was therefore reclassified as an A delta fibre. The responses of 30 electrically identified periodontal C fibres were tested by mechanical, thermal and chemical stimuli applied to the periodontal space. Thirteen of 19 periodontal C fibres tested responded to a strong mechanical force applied to the tooth from different directions while none could be activated by slight touch. A rudimentary directional sensitivity was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Mengel
M K C
MKC
Institute of Physiology, University of Würzburg, D-8700 WürzburgGermany.
Jyväsjärvi
E
E
Kniffki
K-D
KD
D000818:Animals; D002415:Cats; D003080:Cold Temperature; D004558:Electric Stimulation; D004594:Electrophysiology; D005260:Female; D005881:Gingiva / Q000294:innervation*; D008297:Male; D009412:Nerve Fibers / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D010146:Pain / Q000503:physiopathology; D010812:Physical Stimulation; D013268:Stimulation, Chemical; D014070:Tooth / Q000294:innervation