| Abnormalities of the thyroid axis are associated with psychiatric symptomatology and are thought to play a role in the etiology of depressive disorder. While modelling this condition in animals has proven to be challenging, several models currently exist in which various aspects of this disease can be explored. The current investigation sought to determine what changes, if any, occur in the expression of the four thyroid hormone receptors in rat brains in two separate animal models of depression, learned helplessness and chronic mild stress. We report here that the former displayed relatively few significant changes in receptor expression, while the latter showed significant decreases in TR-α1 expression that were subsequently restored upon imipramine administration. These findings indicate that the nature of the stress used may determine whether alterations occur in receptor expression. Based on results obtained in the chronic mild stress model, we theorize that changes in receptor expression might underlie specific symptoms associated with the depressive state and/or recovery from that state. |
