Effect of Postnatal Hypothyroidism on Nitric Oxide Containing Neurons of Rat Cerebral Cortex

The possible effect of postnatal chemically induced hypothyroidism on NADPH- diaphorase containing neurons in different cortical areas of rat neonates. After parturition, dams divided in two groups. The control group receiving drinking water, and experimental group receiving 0.1% PTU in their drinking water. In different postnatal days (P4, P7, P10, P15, P23, P30), the pups of both groups were examined for weight and growth indices. For NADPH-d histochemical analysis, the pups of each group were anaesthetized and perfused via heart with fixative solution, then their brains were removed, weighted and sectioned in the coronal plane (80? m) with a vibratome. The sections were processed for NADPH-d histochemical staining. From P7, the mean body and brain weights of treated pups were significantly lower than their matched controls. The number and distribution pattern of ND+ neuron changes in different areas. In the first postnatal days, neurons are usually located in deeper layers (V,VI) and gradually increase in superficial layers (II, III). With exeption to P15, in PTU treated group a significantly increase in ND + neurons population is observed in cingulate, Forelimb/Hindlimb and parietal cortical ereas. PTU-treated pups show a shorter dendritic length and less cortical vascularization which is more severe in P23 and P30. We can conclude that the changes in the pattern of ND + neurons is correlated with developmental processes and cereblar lamination. Rapid and significant increase in ND+ nenronal population in hypothyroid group shows that No-containing neurons are highly sensitive to hypothyroidism and possibly play an important role in induction of hypothyroidism effects on cerebral development and function.