ABSTRACT
Nervous system growth and differentiation are intimately interrelated with the presence of thyroid hormones [THs] in early development stages. Hypothyroidism during the fetal and postnatal life results in an irretrievable mental retardation syndrome. Assessment of the effect of 3,5,3- triiodo-L-thyronine [T[3]] on changes in the cerebral neurotransmitters level and its possible mechanism in hypothyroid rat male offspring. Hypothyroidism during pregnancy and lactation in one group [hypothyroid group] was performed by antithyroid drug, methimazole [MMI] that was added in drinking water at concentration 0.02%. Another group [T[3]-treated hypothyroid group] MMI was stopped and animal's offspring were received T[3] [20 micro g/100 g body weight in 0.01 N NaOH, i.p.] for one week. The third group is control group. The hypothyroid state in mothers during pregnancy was confirmed by measuring total thyroxine [TT[4]] and total triiodothyronine [TT[3]] at gestational day 10. At the end of experiment, the offsprings were sacrificed and free thyroxine [FT[4]] and free triiodothyronine [FT[3]] in sera and neurotransmitters [dopamine, norepinephrine and serotonin] and Na, K-ATPase activity were measured in the cerebral homogenate. Maternal hypothyroidism induced a significant decrease in the cerebral level of dopamine [0.10 +/- 0.01 mg/g vs 1.00 +/- 0.11 mg/g, p<0.001], morepinephrine [0.01 +/- 0.001 mg/g vs 0.53 +/- 0.49 mg/g, p<0.001], serotonin [1.32 +/- 0.12 mg/g vs 1.94 +/- 0.08 mg/g, p<0.001] and Na, K- ATPase activity [3.11 +/- 0.27 umol pi/ mg protein vs 4.90 +/- 0.64 umol pi/mg protein, p< 0.001] as compared with euthyroid group. Treatment with T[3] significantly increased the cerebral level of neurotransmitters [0.53 +/- 0.10, p<0.05, 0.43 +/- 0.19, p<0.05 and 1.77 +/- 0.11, p<0.01 respectively] and Na, K -ATPase activity [3.87 +/- 0.48 umol pi/ mg protein] as compared with the hypothyroid group. T[3] supplementation during the postnatal period through its effect on the cerebral Na, K -ATPase effectively reversed the effect of maternal methimazole-induced hypothyroidism on the cerebral level of dopamine, norepinephrine and serotonin