Effects of MK 801 on plasma corticosterone levels in stress-induced reinstatement of cocaine-conditioned animals
De Giovanni, Laura Noemi; Virgolini, Miriam Beatriz; Cancela, Liliana Marina.
luli_deyo@yahoo.com.ar
Previous results from our lab showed that MK 801 blocked the stress-induced reinstatement in an extinguished cocaine-induced conditioned place preference (CPP) in rats. In the present experiments, our goal was to determine if corticosterone, the principal hormone released in response to stress, could influence MK 801 effect on stress-induced reinstatement. Male Wistar rats (220-300g) were conditioned with cocaine (10 mg/kg i.p.) during four alternated drug/vehicle sessions, and later extinguished with successive vehicle associations. On the reinstatement day, animals were injected with MK 801 (0.1 mg/kg i.p.) or vehicle, and subsequently assigned to two groups according to the following treatments: 1) Stressed animals (SA): 30 min-restraint exposure, and 2) Control animals (CA): left undisturbed in their home cages. All groups were then tested in the CPP,and their blood collected for plasma corticosterone determination. Results demonstrate that, although MK 801 enhanced plasma corticosterone levels in SA and CA, non-significant differences were evident between both groups. These results show that neither the stress-induced reinstatement nor its blockage by MK 801 are dependent on the corticosterone response.
