The NMDA receptor antagonist MK-801 abolishes the increase in both p53 and Bax/Bcl2 index induced by adult-onset hypothyroidism in rat.

Hypothyroidism affects neuron population dynamics in the hippocampus of the adult rat, with neuronal damage as the main feature of its effect. This effect is prevented by the blockade of NMDA receptors, which suggests that glutamatergic activity mediates cell death in this condition. Glutamate can also stimulate cell proliferation and survival of newborn neurons, indicating that it can affect different stages of the cell cycle. In this work we measured the expression of specific proteins that control cell proliferation (cycline-D1), cell arrest (p21), damage (p53) or apoptosis (Bax and Bcl2) in the hippocampus of hypothyroid rats treated with the NMDA receptor (NMDAR) blocker MK-801 during the induction of hypothyroidism. The results show that hypothyroidism increases the expression of markers of DNA damage, cell arrest, and apoptosis, but does not affect the marker of cell proliferation. NMDAR blockade prevents the increase on markers of DNA damage and apoptosis, but does not influence cell arrest or cell proliferation. This suggests that hypothyroidism promotes cell death mainly by an excitotoxic effect of glutamate.