Influence of thyroid hormonal status on gene expression for calcium channels in the developing olfactory bulb and cerebellum of the postnatal rat

Voltage gated calcium channels serve a host of physiological functions. Classically, they fall into two primary categories: high-voltage-activated (HVA) or low-voltage-activated (LVA). LVA or T-type calcium channels are known to play a role in various physiological phenomena including modulating neuronal excitability, cardiac conduction and pacemaking activity, mediating hormone secretion and smooth muscle contraction. There is also evidence suggesting they are important for proliferation and differentiation of a variety of cell types although the exact mechanisms are unclear. To investigate the role of T-type calcium channels in neuronal development, our lab measured changes in mRNA expression for the pore-forming alpha1 subunit of the family of T-type calcium genes (CaV 3.1, CaV 3.2 and CaV 3.3) as well as a member of the HVA family (CaV 2.3) with similar properties.; To assess the importance of their expression during postnatal development, we compared transcript levels in two distinct CNS structures (olfactory bulb and cerebellum) and how their maturation is influenced by the presence of thyroid hormones. Previous work in our lab has demonstrated the importance of proper thyroid hormone levels for proper neuronal development, the deleterious effects that result when they are absent as well as the prospects for developmental recovery from a hypothyroid state. Using a reversible method of chemical thyroidectomy, we compared changes in mRNA expression under hypothyroid, hyperthyroid and hypothyroid-rehabilitated rats during normal postnatal development.; Based on our PCR results, it appears that the expression for these calcium channel genes is differentially regulated. In terms of development, the expression is tied more closely to development in the cerebellum than in the olfactory bulb. While expression appears to be regulated developmentally and by thyroid hormones, the effects are varied depending on both the tissue and channel. Taken together, this suggests that thyroid hormones due influence the expression of some calcium channels during postnatal development but the exact nature is unclear given the diversity of calcium channel expression in the mammalian brain.