Recruitment of peripheral-type benzodiazepine receptors after acute stress in chick forebrain membranes: action of Triton X-100.

A significant increase in the number of measurable [3H]Ro 5-4864 receptors was found in forebrain membranes of chicks submitted to 15 min of acute swim stress compared to non-stressed chicks. In addition, low subsolubilizing concentrations of Triton X-100 caused a significant increase in the measurable [3H]Ro 5-4864 receptor number in forebrain membranes from non-stressed chicks. However, this increase caused by Triton X-100 was not observed when tested in forebrain membranes from stressed chicks. In all cases the affinity remained unchanged. These results suggest that: (1) acute stress and Triton X-100 induce receptor increase by enhancing [3H]Ro 5-4864 accessibility to a pool of receptors not detected before stress or in the absence of detergent; (2) the pool of non-measured receptors represents about a third of the total in control chicks; (3) the increments are not additive and could involve receptors coming from the same non-measured pool; (4) the receptor increase during a short time of stress could be explained by recruitment of receptors but not by an increase in the receptor protein biosynthesis; (5) stress induces a maximal recruitment of measurable [-3H]Ro 5-4864 receptors.