NEUROSTEROIDS IN THE BRAIN OF HANDLING-HABITUATED AND NAIVE RATS - EFFECT OF CO2 INHALATION

In rats habituated to the manipulation that precedes killing (handling -habituated) the cerebral cortical concentrations of pregnenolone and progesterone were significantly lower (-57% and -69%, respectively) th an in naive animals. An acute stress, induced by CO2 inhalation, elici ted a marked increase in the concentrations of pregnenolone, progester one and deoxycorticosterone in the brain cortex and hippocampus of han dling-habituated rats. An accepted stress, such as foot shock, also en hanced the brain cortical levels of pregnenolone, progesterone and deo xycorticosterone in handling-habituated rats. These data show that the rat brain cortical and hippocampal steroid content is related to the 'emotional state' of the animal.