Modulation of insulin receptors and catecholamines in rat brain in hyperthyroidism and hypothyroidism.

Insulin receptor activity and its relationship with catecholamines and serotonin were investigated in rat brain using Triton X-100 extracts from total membranes, synaptosomes and choroid plexus in experimental hypothyroidism and hyperthyroidism. Insulin receptor activity was assessed by binding to [125I]insulin and catecholamines by high performance liquid chromatography. In choroid plexus thyronines effects are well pronounced and there is modulation vis a vis plasma hormone concentrations. Triiodothyronine levels increase in brain in all experimental groups. This suggests that rat may serve as a useful model for thyronine homeostasis in brain and there may be involvement of very complex regulatory mechanisms in glucose tolerance.