De Giovanni Laura Noemi1, Virgolini Miriam Beatriz1, Cancela Liliana Marina1

1IFEC-CONICET. Dpto de Farmacología, Facultad de Ciencias Químicas, UNC, Córdoba, Argentina.

lcancela@fcq.unc.edu.ar

In previous results we have showed that using the conditioned

place preference procedure, a single 30-min immobilization stress session

induces the reinstatement of cocaine seeking behavior in animals previously

conditioned with this drug. Moreover, we have also demonstrated that 72

hours after the reinstatement test, these animals reinstate again after a

priming dose of cocaine. Based on recent research that suggests that

the NMDA antagonist, MK 801, blocks cocaine-induced reinstatement,

we aimed to prove that this blockade is also present after stress-induced

reinstatement, providing at the same time further evidence for the shared

neurobiological mechanisms between stress and cocaine. Male Wistar

rats were injected with cocaine 10-mg/kg ip and confined to one of two

compartments in four alternated daily sessions drug/vehicle; being the

preference for each context later evaluated. The extinction phase consisted

in successive associations with vehicle in both compartments. Reinstatement

was evaluated measuring the time spent in each compartment after 30 min

of immobilization stress and, 72 h later, in response to a cocaine priming

injection (5 mg/kg). We demonstrated that a systemic injection of MK 801

(0.01 or 0.02 mg/kg) administered 15 minutes before the stress session,

blocked stress-induced reinstatement and that this blockade persisted for

at least 72 hours when was evaluated in response to a cocaine priming

injection. These results support the hypothesis of a potential role of the

NMDA receptor in the cocaine seeking behaviour induced by stress or

cocaine. Further experiments are designed to identify the contribution of

the reward and memory processes in the long-lasting MK-801 disruptive

effects in addiction