Abstract
A considerable number of drugs are listed up as doping ones for race horses withoutgiving any dependable evidence that the use of such drugs will affect the racing per-formance or the speed of race horses. For the reason given above, a serial investigationwas planned in this laboratory to analyze the influences of doping drugs upon the racingperformance of race laorses experimentally. At first, Zran.v-r-oxocamphor was studied.This camphor derivative is a cardiac stimulant and has been frequently detected fromwinning race horses in Japan in routine post-race urinalysis.Three male horses, 4 to 5 years old, of Thoroughbred breed were used. Intravenoussingle doses of 200 mg (a usual dose) and 2000 mg per anirnal of Zron.v-m-oxocamphor(Vitacampher, Takeda Industries, Ltd., Japan) were tested. A controlled exercise wasemployed (Fig. l) . The influence of the drug upon the cbntrol of speed was observedand radiotelecardiographic recording was also performed before, during, and after theexercise. The results obtained are summarized as follows.l. No behavioral changes occurred to horses administered with these two doses, with an exception of one horse, No. 3, injected with 2000 rug. In this horse, tonic con-vulsion of a short duration (about 2 minutes) developed in the extremities and the neckalmost immediately after the injection.2. Second-degree A-V block (hereinafter referred to as A-V block for short) in-creased in occurrence after Zran, v-m-oxocamphor had beeut administered (Figs. 2 and 5).Furthermore, it increased to take a form of double A-V blocks after 2000 mg had been administered (Fig. 5) . These blocks disappeared during the exercise.3. The heart rate decreased in some cases during the exercise after administrationwith Zran.v-m-oxocamphor (Figs. 3, 6, and 10) . In addition, the R-R interval time-seriesfluctuated very irregularly at walking and undulated periodically with a large amplitudeand sudden prolongations appeared at trotting after administration with a dose of 2000mg (Fig. 7-B, horse No. 2). These changes seern in the R-R interval time-series and theoccurrence of double A-V blocks after administration with 2000 mg seemed to be themanifestation of intoxication-like influences on the cardiac function.4. The heart rate in the very early stage of recovery (0 -5 minutes) was relativelylow in some of the horses administered with Zroo.s-m-oxocamphor (Figs. 3 and 6).5. Regardless of its dose administered, Zron.w-r-oxocamphor was not potent enoughto disturb the control of speed (Figs. 4 and 9).6. Generally speaking, marked individual differences were shown in the above-mentioned responses to Zraov-m-oxocamphor.These findings suggest that the influence of Zran.v-m-oxocamphor, at least in a usualdose, may be negligible upon the speed, although a feeble and uncertaitt effect on thecardiac function is not deniable.
