ABSTRACT
Everybodyknowsaboutdrugtolerance.Themoreyoudrink,themorealcoholyou needtogetdrunk;themoreheroinyoutake,themoredrugyouneedtogethigh.But whathasthisgottodowithdrugdependence?Whyshouldthecontinuedtakingof adrugleadtoastatewhereyoucannotdowithoutthedrugeithermentallyor physically?Theanswerprobablyliesinthewayourbrainshaveevolvedtocontrol theirfunctioninginthefaceofalterationsintheinternalorexternalenvironment. Thenervecellswhichmakeupthebrainarehighlycapableofadaptingtonovel situationsandthepresenceofanaddictivedruginthebrainisjustsuchanovel situation.Facedwithanaddictivedrug,nervecellsgraduallycompensateforits presencesothattheyreturntorelativelynormalfunctioning,eveninthepresenceof thedrug.Thisiswhatunderliesdrugtolerance-theabilityofthebraintofunction athigherandhigherconcentrationsofthedrug.
