Spontaneously hypertensive rats and Lewis rats differ in their anxiety levels and in their serotonergic and corticotropic responses to stress. Since the 5-HT transporter plays a key role in 5-HT neurotransmission, we have analyzed whether hippocampal and/or striatal [ 3 H]5-HT reuptake kinetics are altered by stress in a strain-dependent manner. It was found that forced swimming, treadmill running, or restraint for 30 min affected neither hippocampal nor striatal [ 3 H]5-HT reuptake K m and V m a x values in the two rat strains. This study, which is the first to examine the impact of acute stress on [ 3 H]5-HT reuptake with respect to the nature of the stressor, the brain region analyzed, and the rat strain, could reinforce the hypothesis that extracellular 5-HT levels during stress are representative of 5-HT release.