Benzodiazepine receptors increase induced by stress and maze-learning performance in chick forebrain

Two-day-old chicks were selected on their second escape performance in a one-trial, maze-learning task, and termed high-performance (H-P), moderate-performance (M-P), and low-performance (L-P) chicks. The learning degree was expressed by the escape time improvement being respectively the 64, 46, and 24%. Then, the three selected groups were maintained to reach 15 days of age and then submitted to acute swimming stress, and [3H]flunitrazepam and [3H]Ro 5-4864 receptor bindings were performed on synaptosomal/mitochondrial membranes from forebrain. The receptor number for both radioligands in stressed high-performance chicks was significantly higher than in stressed low-performance chicks. The results suggest that higher performance chicks were more susceptible than lower performance chicks to acute stress associated to increase of both central and peripheral type benzodiazepine receptors, probably due to differences in the degree of endogenous emotionality.