Effects of neonatal hypothyroidism on the expressions of growth cone proteins and axon guidance molecules related genes in the hippocampus.

During critical periods of development, hypothyroidism causes abnormalities of the central nervous system such as incomplete maturation of neuronal and glial cells, reduction in synaptic densities and myelin deficits. In this study expression of development regulated genes, ie transcription of beta-actin, sema 3F, CRMP 1 to 4, GAP-43, G alpha o1, G alpha o2 and translation of beta-actin, G alpha o, G alpha o1, CRMP-2, CRMP-4 genes were examined in the hippocampus of neonatal methimazole induced hypothyroid rats at the age of day 16. All CRMPs mRNA levels were significantly higher in the hypothyroid rats. Significant higher CRMP-2 protein but not CRMP-4 protein was found in the hypothyroid rats. The neonatal experimental hypothyroid states did not affect the protein levels of beta-actin but up-regulate its mRNA. Transcription of CRMP 1 to 4, GAP-43, G alpha o1 but not G alpha o2 and sema 3F was altered by the neonatal treatment. The only sex difference in gene expression was found in the transcription of CRMP-2 gene.