Effects of an Acute Treatment with L-Thyroxine on Memory, Habituation, Danger Avoidance, and on Na(+), K(+)-ATPase activity in Rat Brain

DOS REIS-LUNARDELLI EA, RAMIREZ MR, CASTRO CC, COITINHO AS, BAVARESCO C, DA TRINDADE LS, PERRENOUD MF, DE SOUZA WYSE AT, SARKIS JJ, IZQUIERDO I.

CURRENT NEUROVASCULAR RESEARCH

BENTHAM SCIENCE PUBL LTD

Año: 2007 vol. 4 p. 184 - 193

1567-2026

Thyroid hormones (THs) have a relevant action on brain development and maintenance. By using an acute treatment to induce a hyperthyroid animal model, we aimed at investigating the effect of an altered THs levels on learning and memory and on the activity of Na(+), K(+)-ATPase in the rat brain. Our results have shown that the acute treatment with L-T4 did not alter the retrieval of the inhibitory avoidance task, but had a significant effect on the elevated plus maze and on open-field performance in rats. We suggest that animals subjected to L-T4 administration improved the habituation to a novel environment as well as a better evaluation of a dangerous environment, respectively. Na(+), K(+)-ATPase activity is increased in parietal cortex (30%), but it is not altered in hippocampus in L-T4 treated group. These both brain structures are involved in memory processing and it was previously demonstrated that there is a double dissociation between them for spatial location information, perceptual and episodic memory. We propose the hypothesis that this increase of Na(+), K(+)-ATPase activity in parietal cortex may be correlated to our results in behavior tests, which suggest a role of THs as well as of the Na(+), K(+)-ATPase in the cognitive process.