Effect of steroid competition and time on the uptake of (3H)corticosterone in the rat brain; an autoradiographic study.

The localization of [3H]corticosterone in the brain and pituitary of the adrenalectomized rat was studied by autoradiography. Corticosterone was concentrated preferentially by neurons in the hippocampus, septum, amygdala, and neocortex, with the hippocampal and septal neurons having the greatest concentration. [3H]-Corticosterone localization was significantly greater in neurons from adrenalectomized animals. Administration of unlabeled corticosterone (3 mg) 30 min before injection with [3H]corticosterone significantly decreased cellular localization of the labeled corticosterone, whereas [3H]corticosterone localization was not affected by progesterone pretreatment. Animals were sacrificed 15, 30 and 120 min after the injection of [3H]corticosterone to study the distribution of the hormone over the cytoplasm and nuclei. Silver grains were localized primarily over the cytoplasm of the concentrating neurons 15 min after injection; however, by 30 min after injection they were evenly distributed over both nuclei and cytoplasm.