Differential effects of dopaminergic agents on locomotor sensitisation and on the reinstatement of cocaine-seeking and food-seeking behaviour.
BACKGROUND
The dopaminergic pathways are involved in natural and drug reward related processes.


OBJECTIVE
To compare the respective involvement of the dopaminergic receptors D1, D2 and D3 in natural-seeking versus drug-seeking behaviour and evaluate any concomitant expression of locomotor sensitisation.


METHODS
In separate experiments, male Wistar rats were trained to self-administer cocaine (0.25 mg/infusion) or to press a lever to obtain food pellets. Following a prolonged period of extinction, reinstatement of lever responding was measured following non-contingent food delivery, cocaine (15 mg/kg), D1-like (SKF 82958, 0.25 mg/kg), D2-like (quinelorane, 0.25 mg/kg) and D3-like (7-OHDPAT, 0.25 mg/kg) agonists. To demonstrate parallel expression of behavioural sensitisation, locomotor activity was recorded during the reinstatement sessions.


RESULTS
Cocaine and quinelorane administrations reinstated cocaine-seeking behaviour and induced the expression of locomotor sensitisation, whereas SKF 82958 and 7-OHDPAT had either no effect or non-specific effects. In the food-seeking experiment, we found that quinelorane and 7-OHDPAT did not reinstate lever pressing. Cocaine increased responding on both active and inactive levers, whereas SKF 82958 had a more specific effect with higher responding on the previously food-associated lever.


CONCLUSIONS
Our results indicate that expression of locomotor sensitisation and reinstatement of cocaine-seeking but not food-seeking behaviours are in part supported by common dopaminergic substrates, among which the D2 receptors play a crucial role.
Dias
C
C
Laboratoire de Neuropsychobiologie des Désadaptations, UMR CRNS 5541, Université Victor Ségalen, Bordeaux 2, 146, rue Leo Saignat, BP 31, 33076 Bordeaux Cedex, France. d_carine@yahoo.fr
Lachize
S
S
Boilet
V
V
Huitelec
E
E
Cador
M
M
D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology; D019970:Cocaine-Related Disorders / Q000523:psychology*; D003463:Cues; D018491:Dopamine Agonists / Q000494:pharmacology*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D005108:Extinction, Psychological / Q000187:drug effects; D005247:Feeding Behavior / Q000187:drug effects*; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D010775:Photic Stimulation; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000819:agonists; D017448:Receptors, Dopamine D2 / Q000819:agonists; D050637:Receptors, Dopamine D3; D012008:Recurrence; D012201:Reward; D013764:Tetrahydronaphthalenes / Q000494:pharmacology
D001552:Benzazepines; D018491:Dopamine Agonists; D018765:Dopamine Uptake Inhibitors; C493595:Drd3 protein, rat; D011804:Quinolines; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D013764:Tetrahydronaphthalenes; C071262:SK&F 82958; D003042:Cocaine; C031349:7-hydroxy-2-N,N-dipropylaminotetralin; C047726:quinelorane