AIMTo observe the effects of sustained electrical stimulation at Bötzinger complex (Böt. c) on phrenic nerve discharges.

METHODSSustained electrical stimulation (10--50 microA, 40-100 Hz, 0.3 ms, for 15-30 s) of Böt. C on 30 urethane anaesthetized, vagotomized, paralyzed and artificially ventilated rabbits.

RESULTSSustained electrical stimulation of Bot. C produced the inhibition or "inspiratory off-switch" of phrenic discharge during the stimulation. The inhibition of the phrenic discharges showed intensity and frequency dependence. Habituation was shown during the stimulation, showing the magnitude of the phrenic nerve discharge increased gradually. Post-stimulus rebound exhibited upon the cessation of the stimulation, showing the magnitude of the phrenic activity increased significantly. Short-term memory was shown in the habituation of the phrenic activity.

CONCLUSIONNon-associative learning is involved in the central control of respiratory modulation in the Böt. C and synaptic plasticity may exist in the respiratory neurons of Böt. C.

Animals ; Electric Stimulation ; Facial Nerve ; physiology ; Neurons ; physiology ; Phrenic Nerve ; physiology ; Rabbits

Experiments were done on urethane anesthetized adult rabbits. Long-train electrical stimulation was delivered to the Bötzinger complex (Böt.C) to observe the changes in the peak amplitude of integrated phrenic nerve activity. Then, a long-train electrical stimulation was delivered to the locus coeruleus (LC) or monosodium glutamate was microinjected into the LC . Within a certain period of time, another long-train electrical stimulation was delivered to the Böt.C to observe the responses of phrenic nerve activity. We investigated whether the LC could modulate the inspiratory inhibition induced by electrical stimulation of the Böt.C. The results are as follows: (1) Within a certain period of time after a long-train electrical stimulation applied at the LC, the inspiratory inhibition produced by electrical stimulation at the Böt.C was significantly attenuated. Comparing with the control stimulation that was only delivered at Böt.C without pre-stimulation of the LC, the inspiratory inhibition was decreased by (28.78+/-19.49)%. (2) Similarly, after chemical stimulation of the LC with microinjection of monosodium glutamate, the inspiratory inhibition produced by electrical stimulation of Böt.C was also significantly attenuated [decreased by (19.18+/-8.06)%]. The results obtained suggest that the LC plays a role in the modulation of the inspiratory inhibition of Böt.C stimulation.
Animals ; Electric Stimulation ; Electrophysiology ; Female ; Locus Coeruleus ; physiology ; Male ; Medulla Oblongata ; physiology ; Microelectrodes ; Microinjections ; Neurons ; physiology ; Phrenic Nerve ; physiology ; Rabbits ; Respiration ; Sodium Glutamate ; pharmacology ; Urethane ; pharmacology

The assessment of diaphragmatic function has received increasing attention in recent decades because of successful clinical application of the electrophrenic pacemaker. Knowledge of the normal value of the phrenic nerve conduction latency according to Korean physical characteristics may be helpful when choosing electrophrenic respiration candidates and for evaluation diaphragmatic function postoperatively. Therefore in this study we have put the emphasis on obtaining the mean value of the phrenic nerve conduction latency in 18 healthy Korean adults and have correlated the effect of the intercathodal distance and the height of the subject with the conduction latency. As a result the mean conduction latency for the phrenic nerve was 7.10 msec (SD 0.14) and the mean intercathodal distance was 33.2cm (SD 0.41). Significant positive correlations of intercathodal distance with conduction latency and with subject height were found.
Adult ; Age Factors ; Body Height ; Female ; Human ; Korea ; Male ; Middle Age ; Neural Conduction* ; Phrenic Nerve/physiology* ; Reaction Time

The mRNA and protein expression of skeletal dihydropyridine receptor isoform alpha1 subunit (DHPR(alpha1)) and ryanodine receptor(1-3) (RyR(1-3)) during chronic electrical stimulation (CES) of phrenic nerve have rarely been explored. In the present study, we explored the signal translation mode of calcium release unit in diaphragm muscle of rabbits after CES. Thirty rabbits were used and randomly divided into the normal, 10, 20, 50 and 100 Hz groups. Phrenic nerve was continuously (5 weeks, 2x 2 h/d) stimulated at 10, 20, 50 and 100 Hz respectively (impulse width 0.2 ms, 3~6 waves/time, 45 times/min, 10~20 V). Reverse transcription PCR and immunohistochemical methods were employed. The results showed that mRNA and protein expressions of DHPR(alpha1) and RyR(1) in 10 and 20 Hz groups were more significantly lower than those in the control group (P<0.01), but mRNA and protein expressions of DHPR(alpha1) and RyR(1) were significantly higher in 50 and 100 Hz groups than those in the control group (P<0.01); a lower level of mRNA expression of RyR(2) was found in 10 and 20 Hz groups. It is suggested that the calcium release unit and the signal transduction mode between DHPR and RyRs were altered from conformational changes of linked proteins to Ca(2+)-induced Ca(2+) release (CICR) in the diaphragmatic muscle of rabbits after chronic low-frequency electrical stimulation of phrenic nerve for 5 weeks.
Animals ; Calcium ; metabolism ; Calcium Channels, L-Type ; biosynthesis ; genetics ; Diaphragm ; metabolism ; physiology ; Electric Stimulation ; Female ; Male ; Muscle, Skeletal ; metabolism ; physiology ; Phrenic Nerve ; metabolism ; physiology ; RNA, Messenger ; biosynthesis ; genetics ; Rabbits ; Random Allocation ; Ryanodine Receptor Calcium Release Channel ; biosynthesis ; genetics