Medullary post-inspiratory neuronal and diaphragm post-inspiratory activities during spontaneous augmented breaths in anesthetized rats.
To test the hypothesis that during augmented breaths the prolonged expiratory time is correlated with the activity of medullary post-inspiratory neurons, changes in diaphragm electromyogram and post-inspiratory neuronal activities were examined in pentobarbital anesthetized rats. During augmented breaths, the mean total expiratory time significantly increased (from 0.57 +/- 0.02 to 1.20 +/- 0.07 s, P < 0.01), but the mean duration of post-inspiratory inspiratory activity (PIIA) was significantly decreased (from 0.08 +/- 0.01 to 0.02 +/- 0.003 s, P < 0.01) compared to control breaths. The mean time which the diaphragm was electrically silent was observed to be significantly prolonged during augmented breaths (from 0.48 +/- 0.02 to 1.19 +/- 0.07 s, P < 0.01). During significant prolongations of expiratory time in augmented breaths, most of the recorded neurons (9/10) in the medulla showed sustained discharges. The mean duration of discharges was longer than that of PIIA (0.02 +/- 0.003 vs. 0.50 +/- 0.10 s, P < 0.01). The mean firing frequency/breath significantly increased compared to control breaths (9.45 +/- 1.69 vs. 37.6 +/- 7.13 imp/breath, P < 0.01). These results suggested that during augmented breaths, the prolonged expiratory period may not be mediated by persisting post-inspiratory neuronal activity in the medulla.
Takeda
M
M
Department of Physiology, School of Dentistry, Nippon Dental University at Tokyo, Chiyoda-ku, Japan.
Matsumoto
S
S
D000758:Anesthesia; D000818:Animals; D003964:Diaphragm / Q000502:physiology*; D004576:Electromyography; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration / Q000502:physiology*; D013997:Time Factors