ABSTRACT
Over the last 20-30 year the availability of drug with high pecificity and electivity have offered an alternative trategy. Small molecule acting on receptor a agoni t or antagoni t or on enzyme a activator or inhibitor permit elective functional modification over the hort or long term. Ob erving the con equence yield information on function and the course of the di ea e in que tion . Thu , modern drug offer the additional po ibility of controlled tudie of pathophy iological mechani m a well as achieving their primary objective of uppre ing ymptom or modifying di ea e expre ion or progre ion.
