Response of the rat brain β-endorphin system to novelty: Importance of the fornix connection

摘要: In control rats, a step-down inhibitory avoidance training trial using 0.8 mA footshock, or simple exposure to the apparatus without was followed by decrease of β-endorphin-like immunoreactivity measured in hypothalamus and ventral thalamus. The effect also rats submitted brain sham operation, bilateral transection dorsal fornix, anterior posterior hypothalamic deafferentation, adrenal medullectomy, an 16 daily ip injections 0.2 mg/kg dexamethasone, 1 ml/kg saline. diencephalic response abolished fornix unaffected all other treatments. This suggests that is not mediated neural afferents hypothalamus, hypersecretion epinephrine medullae, ACTH pituitary gland. response, instead, appears require integrity pathway sends projections from septo—hippocampal system hypothalamus. Previous evidence had suggested result novelty, has been postulated play role registration novelty.