Relationships of plasma catecholamines to open-field behavior after inescapable shock.

Male rats with indwelling jugular catheters were exposed to inescapable shock or no shock, and ambulation and defecation were measured 24 h later in an open field. Plasma catecholamine levels were determined from blood samples taken before and during pretreatment as well as before and after testing for aftereffects on open-field behavior. Shocked animals showed higher plasma catecholamine levels during the shock session and lower locomotor activity in the open field. Open-field activity was negatively correlated in shocked animals with both plasma catecholamines before and during shock and also with plasma epinephrine before open-field testing. Defecation was only positively correlated with plasma norepinephrine before open-field testing. Thus, the reduced open-field activity after inescapable shock may indicate heightened fear or anxiety which may also be present when shocked animals are tested for their performance in more complex tasks.