抄録
We studied effects of Doxapram HCl on the heart rate variability known as a major source of the cardiopulmonary modulation. The experiments were carried out using adult Wister rats under urethane anesthesia. The electric stimulation was applied to right cervical vagal nerves with and without blocking of afferent conduction. The drug was delivered from the inguinal femoral vein. Frequency analysis, autocorrelation-FFT method was applied to extracted time domains characterized by RR, PP, QT and PR intervals to obtain respective power spectra. The respiration induced component in the RR spectrum nearly identical to that of PP spectra, whereas much small amplitude in QT and PR spectra. When the vagal nerves were blocked bilaterally, the respiration became slow and lowered PP and PR intervals. The variability was less correlated to the respiration, in some cases provided double peak in PR and QT spectra. When the drug was administrated, the respiration amplitude was significantly increased and restored the variability. It further lowered the PP intervals, but significantly increased PR intervals. Elevated respiratory amplitude by Doxapram HCl administration was not affected by electric stimulation after vagal blocking. It also increased the heart rate variability component synchronized to respiratory rhythm. The present findings strongly suggested that Doxapram HCl may act in the respiration center stimulating cardiopulmonary reflex to balance the pulmonary and body circulations. [Jpn J Physiol 54 Suppl:S111 (2004)]
