[Electrophysiological properties of fast- and slow-adapting units and their generator potentials of the frog tongue].

Abstract

The purpose of this study was to determine the stimulus response properties of fast and slow adapting units in the fungiform papillae of the frog tongue. Secondly, fast- and slow- adapting generator potentials were recorded from fast and slow-adapting mechanoreceptors in the single fungiform papilla glossopharyngeal nerve preparations, respectively. Results I. Impulse response properties of fast- and slow-adapting units 1) Most of the fungiform papillae were innervated by both fast- and slow-adapting units. Fast-adapting units evoked 1-4 impulses to each stimulus and the adaptation time was less than 17.5 msec. Slow-adapting units evoked 27.8 +/- 8.0 impulses (range: 11-49 impulses n = 18) during a pressure stimulation of 3 sec, and the adaptation time was 1.64 +/- 0.73 sec (range: 0.53-2.86 sec, n = 18). 2) Threshold, latency and absolute refractory period for fast-adapting units were 7.0 +/- 1.9 microns (range: 3.0-11.8 microns, n = 189), 2.31 +/- 1.29 msec (range: 0.85-6.80 msec, n = 31) and 2.9 +/- 1.0 msec (range: 1.8-5.6 msec, n = 33), respectively. Those for slow-adapting units were 4.6 +/- 1.8 microns (range: 2.0-11.8 microns, n = 152), 13.54 +/- 11.29 msec (range: 2.00-54.00 msec, n = 35) and 6.5 +/- 3.6 msec (range: 1.9-19.6 msec, n = 35), respectively. 3) A fast-adapting unit innervated 5.1 +/- 2.5 fungiform papillae (range: 1-13 fungiform papillae, n = 58) and the receptive area was 0.342 +/- 0.312 mm2 (range: 0.005-1.548 mm2, n = 55). A slow-adapting unit innervated 3.3 +/- 2.0 fungiform papillae (range: 1-12 fungiform papillae, n = 50) and the receptive area was 0.158 +/- 0.144 mm2 (range: 0.006-0.616 mm2, n = 29). 4) Conduction velocity of the fast-adapting unit was 23.0 +/- 3.1 m/sec (range: 15.0-30.6 m/sec, n = 528) and that of the slow-adapting unit was 12.8 +/- 2.2 m/sec (range: 4.4-21.1 m/sec, n = 495). The conduction velocity was calculated from the time necessary to conduct at two different points of the nerve fiber. 5) The upper limits of fast- and slow-adapting units for vibratory stimulation were 62.7 +/- 10.5 Hz (range: 50-80 Hz, n = 15) and 34.5 +/- 9.6 Hz (range: 15-45 Hz, n = 10), respectively. II.(ABSTRACT TRUNCATED AT 400 WORDS)