Possible Influence of Dopaminergic Receptor in Maintenance of Thyroid Hormone Homeostasis: A Study in Adult Rat Brain

Abstract

Background: The role of thyroid hormone (TH) disbalance in genesis of psychological disturbances in the adult humans is well known. A phenomenon of ‘central thyroid hormone homeostasis’ characterized by increased synaptosomal T3 content, deiodinase type II (DII) activity and cAMP level, is known to exist during peripheral hypothyroidism. This phenomenon tries to counteract the adverse psychobehavioural manifestations commonly associated with TH deficiency. A close physiological association between sympathetic nervous system activity and TH is well known. Dopamine, a predominant catecholamine neurotransmitter in the mammalian brain, controls a variety of functions including locomotion, cognition, emotion and also affects neuroendocrine secretion. In the present study relationship between TH and dopamine has been presumed to be involved in the maintenance of ‘central thyroid hormone homeostasis’ in adult rat. 

Methods: We injected specific dopaminergic receptor agonists and antagonists along with an antithyroid drug (PTU) to find out any effect on ‘central homeostasis’ in adult rat. 

Results: The dopaminergic agonist did not alter the onset of ‘central homeostasis’, but prolonged its duration by maintaining the control level of cerebral T3. Injection of the antagonist did not cause any perturbation. These results have been supported by parallel changes in cerebrocortical DII activity and cAMP. 

Conclusion: In the present experiment a striking feature is that a D₂-receptor mediated inhibition of cAMP accumulation has been reversed to D₁-receptor mediated stimulation of cAMP accumulation probably by the effect of ‘central thyroid hormone homeostasis’. This effect of D₂-agonist can be therapeutically utilized for prolonging the duration of homeostasis.




doi:10.4021/jem101w