[Oscillation of impulse discharges of Pacinian corpuscles of cat mesentery to external stimulation]

A sensory unit with one or two Pacinian corpuscles was isolated from cat mesentery and square wave mechanical stimulation (duration 5-10 sec), sinusoidal frequency stimulation (duration 4-130 sec, frequency 0.06-300 Hz) and ramp mechanical stimulation (duration 5-10 sec) were applied to the Pacinian corpuscles. When the temperature exceeded 27 degrees C, the sensory unit caused a sustained discharge after on-response to the square wave stimulation. The sustained discharge lasted until the off-response. The sustained discharge was considered to be generated by an oscillation of the receptor potential in the Pacinian corpuscles. The results were as follows: 1. Sensory units with two Pacini corpuscles of cats from young (20 days after birth) to adult were found to respond with both fast-adapting and apparent slow-adapting responses at room temperature (27 degrees C). 2. The two Pacini corpuscles showed the characteristics of fast-adapting mechanoreceptor and vibrator. It was confirmed that the apparent slow-adapting responses from the sensory units were not artifacts induced by vibration from the stimulating bar or experimental table or experimental room, but were originated by an unknown mechanism in the corpuscles. 3. Some sensory units with two Pacinian corpuscles also responded with both fast-adapting and apparent slow-adapting responses in the range of 27-29 degrees C. The apparent slow-adapting responses were caused by pressure and vibratory stimulations above a strength level, but not by dumping of the stimulating bar. 4. The sensory unit evoked only the fast-adapting discharges near the threshold level of stimulus strength at less than 27 degrees C. In the temperature range of 27-40 degrees C, the sensory unit showed an increase in frequency of the apparent slow-adapting discharge by increased displacement and velocity of the stimulus. 5. The sensory unit responded with repeated firing to low-frequency stimulation (0.1-0.06 Hz) at the temperature range and the impulse number was increased by increased strength of the low-frequency stimulation. 6. At the 27-40 degrees C, the sensory units with Pacinian corpuscles evoked after discharge and spontaneous discharges and the impulse number was increased by increased displacement, velocity and frequency of the mechanical stimulus. Thus it is difficult to call the response of Pacinian corpuscles observed at more than 27 degrees C a slow-adapting one, judging from the duration of the receptor potential. We considered that these discharge responses resulted from an electrical oscillation of the receptor potential in the corpuscles.(ABSTRACT TRUNCATED AT 400 WORDS)