Abstract
We studied effects of doxapram HCl on the cardiopulmonary system using adult Wister rats under urethane anesthesia. The drug was delivered from the inguinal femoral vein. The effect of drug was evaluated by RR, PP and QaT intervals from ECG with and without blocking of cervical vagal nerves and pre-administration of atropine. ECG and respiration wave were recorded by using Biopac MP-30 system.Frequency analysis was performed from extracted time domains characterized by RR, PP and QaT intervals with fast FFT to obtain respective power spectra. When the vagal nerves were electrically stimulated, the drug mitigated the inhibition of the respiration. A blocking of the vagal nerves bilaterally, the drug did not relief the inhibition on neither respiration nor HR. When atropine sulfate was administrated prior to the doxapram HCl, the electric stimulation resulted in the inhibition of the respiration, but no effect on the HR. Regarding the cardiac conduction times, the bilateral blocking of the vagal nerves resulted in shorten PP and PR intervals and no change in QaT. The atropine sulfate administration provided essentially the same results as the vagal nerve blocking. By contrast, doxapram HCl administration significantly elongated the QaT intervals where as the PP interval was shorten. This imply that the drug affect to elongate the repolarization time of ventricles and shorten the atrium contraction and atrio-ventriclar conduction. [Jpn J Physiol 55 Suppl:S99 (2005)]
