The effect of repeated mild stress on cerebral cortical adrenoceptors and noradrenaline synthesis in the rat.

The effects of repeated mild stress on cortical alpha 2- and beta-adrenoceptor binding sites and on the rate of noradrenaline synthesis in cortical synaptosomes were measured. The stressful stimuli were either daily handling (1 min) or daily handling which included an i.p. saline injection. In both cases, rats killed 24 h after the last of 14 daily treatments showed an increase in noradrenaline synthesis rate and a decrease of alpha 2- and beta-adrenoceptor density. There were no changes in adrenoceptor density or the noradrenaline synthesis rate after either a single or 5 daily handlings plus saline injections. At no time was a change found in the Kd of either alpha 2- or beta-adrenoceptor binding sites. The results are discussed in relation to the effects on adrenoceptors of chronic antidepressant treatments.