Initial experience of heroin use under a two-chained operant schedule influences drug-seeking behavior after one month of abstinence.
OBJECTIVE
To evaluate the influence of an initial heroin experience under a modified two-chained training schedule on drug-seeking behavior after a long abstinence period.


METHODS
Rats were trained to respond for intravenous heroin (120 microg/kg) under a heterogeneous chained schedule of reinforcement using different responses in the first and second links of the chain. Animals received low-frequency drug administration training for four days and were then subjected to one month of abstinence in their home cages. Heroin-seeking behavior induced by re-exposure to the first chain associated context or discriminative stimuli was assessed after abstinence.


RESULTS
Almost all animals could acquire operant skills quickly under the two-chained schedule training for four days, as measured in first active response latency, travel speed and goal-box enter latency. Both first chain associated context and discriminative stimulus could reinstate heroin-seeking behavior after one month abstinence.


CONCLUSIONS
These observations suggest that an early experience of drug use is sufficient to maintain heroin-seeking behavior even after a one month abstinence.
State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
Bin
B
Lu
Mu
M
Li
Yuan-yuan
YY
Hou
Jie
J
Chen
Zhi-qiang
ZQ
Chi
Jing-gen
JG
Liu
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003216:Conditioning, Operant / Q000187:drug effects; D003932:Heroin / Q000008:administration & dosage* / Q000494:pharmacology; D006556:Heroin Dependence / Q000209:etiology*; D008297:Male; D009294:Narcotics / Q000008:administration & dosage* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D009294:Narcotics; D003932:Heroin