Intermittent versus continuous stimulation: effect of time interval on the development of sensitization or tolerance

Studies from several disciplines support the concept that the temporal characteristics of repeated drug, electrophysiological, or psychological stimuli can affect the direction of cellular and behavioral adaptation. While chronic, continuous stimulation is often associated with the development of tolerance, intermittant stimulation, under some circumstances, may have the opposite effect and be associated with sensitization or reverse tolerance. While many other variables can affect the development of sensitization or tolerance, it is suggested that the interval between electrical, drug, or psychological stimuli is important in determining subsequent responsivity. Temporal characteristics should be carefully considered both in relation to experimental design and theoretical implications; they may shed light on similarities and differences in mechanisms underlying tolerance and sensitization.