Table 1. A possible systematics on the modifications of the response to an effector.

object of the modification	value	modifier do not promotes response (perturbations)	modifier is another effector (interactions)
effective dose corresponding to the nominal dose	higher	POTENTIATION	SYNERGY
	lower	DEPRESSION	ANTAGONISM
number of active receptors	higher	STIMULATION	ACTIVATION
	lower	INHIBITION	INACTIVATION
threshold	higher	INSENSITIZATION	ATTENUATION
	lower	SENSITIZATION	ENHANCEMENT

When the modifier is a second effector (interactions), unidirectional and reciprocal effects can be considered in every case. For details, see text.