Learning, brain noradrenaline and the pituitary--adrenal axis
Ogren, S.O.; Fuxe, K.
Medical Biology 52(6): 399-405
1974
ISSN/ISBN: 0302-2137 PMID: 4374613 Document Number: 81100
The noradrenaline (NA) pathways to the forebrain were degenerated by 6-hydroxydopamine (6-OH-DA) injection into the coerulo-cortico (dorsal) bundle of animals (rats) trained on a conditioned avoidance response (CAR). The 6-OH-DA injection alone did not significantly impair the retention of the CAR compared to sham-operated animals. When the 6-OH-DA lesion was combined with adrenalectomy there was a marked reduction of the retention of CAR and a complete failure to relearn the CAR. The coerulo-cortical bundle may not be essential for the performance of a conditioned avoidance response and its loss can be compensated for provided that the pituitary-adrenal axis is intact. The 6-OH-DA lesion plus adrenalectomy also lowers the activity in the open field and the response to pain. There may also exist an interaction between the NA neurons and the pituitary-adrenal axis in the control of motor activity and pain.