TY - JOUR
T1 - Endogenous opiate reward induced by an enkephalinase inhibitor, thiorphan, injected into the ventral midbrain
AU - Glimcher, P. W.
AU - Giovino, A. A.
AU - Margolin, D. H.
AU - Hoebel, B. G.
PY - 1984
Y1 - 1984
N2 - Opiates are known to be reinforcing when injected into the ventral tegmental area (VTA). The present study produced conditioned reinforcement with local injections of exogenous d-ala2-met5-enkephalinamide (DALA), a potent analogue of met-enkephalin, and with thiorphan, an enkephalinase inhibitor which protects endogenous opiates from enzymic degradation. In a conditioned place preference paradigm, rats received injections of DALA (1.0, 3.0, or 8.0 μg), thiorphan (60 μg), and/or naloxone (10 μg), or saline vehicle. Conditioned reinforcement was obtained with 8.0 μg of DALA and also with thiorphan but not with thiorphan plus naloxone. This suggests that reward can be generated by endogenous opiates in the VTA. Tests during the light phase and dark phase suggested that diurnal periodicity may play a role in opiate reward. It is concluded that the VTA can generate conditioned reward through transmitter-receptor interaction involving an endogenous opiate substrate which is probably enkephalinergic.
AB - Opiates are known to be reinforcing when injected into the ventral tegmental area (VTA). The present study produced conditioned reinforcement with local injections of exogenous d-ala2-met5-enkephalinamide (DALA), a potent analogue of met-enkephalin, and with thiorphan, an enkephalinase inhibitor which protects endogenous opiates from enzymic degradation. In a conditioned place preference paradigm, rats received injections of DALA (1.0, 3.0, or 8.0 μg), thiorphan (60 μg), and/or naloxone (10 μg), or saline vehicle. Conditioned reinforcement was obtained with 8.0 μg of DALA and also with thiorphan but not with thiorphan plus naloxone. This suggests that reward can be generated by endogenous opiates in the VTA. Tests during the light phase and dark phase suggested that diurnal periodicity may play a role in opiate reward. It is concluded that the VTA can generate conditioned reward through transmitter-receptor interaction involving an endogenous opiate substrate which is probably enkephalinergic.
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U2 - 10.1037/0735-7044.98.2.262
DO - 10.1037/0735-7044.98.2.262
M3 - Article
C2 - 6586195
AN - SCOPUS:0021367028
SN - 0735-7044
VL - 98
SP - 262
EP - 268
JO - Behavioral Neuroscience
JF - Behavioral Neuroscience
IS - 2
ER -