Opiate withdrawal: the result of conditioning or physiological mechanisms?

Although it has been suggested that opiate withdrawal responses might be conditioned compensatory responses elicited by drug-associated stimuli, the present results do not support such a view. Withdrawal, as measured by an aversion to a saccharin solution following the termination of morphine administration, occurred independent of the presence of morphine-paired environmental or temporal cues. These results suggest that withdrawal is most likely the result of some physiological mechanism, rather than the result of conditioning.