Effects of bilateral lesions in thalamic reticular nucleus and orbitofrontal cortex in a T-maze perseverative model produced by 8-OH-DPAT in rats.

OBJECTIVE

Stereotaxic lesions of the orbitofrontal-thalamic system, specifically the thalamic reticular nucleus (TRN), could be helpful to prevent perseverative behavior in rats produced by 8-OH-DPAT.

METHODS

Fifty rats were conditioned in a T-maze to measure the number of perseverations. Habituation was performed on days 1 and 2, baseline scores were obtained on day 3 and the final test was done on day 4 (chemical induction). Group I only received saline solution injection; group II was only submitted to 8-OH-DPAT; group III received pharmacological treatment with chlorimipramine (CMI) before 8-OH-DPAT administration; group IV and group V were submitted to stereotaxic bilateral lesions, one week before T-maze evaluation, in the TRN and orbitofrontal cortex (OFC), respectively and received 8-OH-DPAT administration.

RESULTS

No differences between groups were found at baseline on day 3 (p<0.05). Significant differences were found between days 3 and 4 of evaluation only in group II (p<0.01) and group V (p<0.001). Differences between groups on day 4 were significant (p<0.01).

CONCLUSIONS

TRN lesions were as effective as CMI administration to prevent the 8-OH-DPAT action. OFC lesions failed to prevent the perseverative behavior.