Quite easily actually (although there's no such thing as "blood pressure", -I'm taking it as that you mean systolic?).
Artificially increase the pulse rate. The brain compensates by decreasing stroke
volume so as to restore cardiac output, and since stroke volume is directly proportional to pulse pressure (at the aortic valve
), pulse pressurePp is also reduced. Mean pressure is restored, -that's how the brain works.
Now, since "systolic pressure = mean pressure + 2/3rds of pulse pressure", systolic pressure is reduced.
Q.E.D., as they say.
Not really sure why you'd want to be doing it though as the risk of fainting
P.S., -you increase the pulse rate with a pacemaker (demand) either internal or external.
It's much easier to do it with drugs, of course, but you specify without medication.
Do you count alcohol as medication? It's great for getting all your B/P's down. (temporarily!) Just keep drinking steadily and keep taking your systolic and diastolics at 10 minute intervals........they come down before your very eyes, -like a dream. Scientifically beautiful to observe. And count the pulse-rate rise simultaneously. Everyone should do it just once, for the sheer exhilaration of watching theory work in practice.
"HIC"! ....( Pardon, excuse me. )