Effect of 3, 5, 3 -triiodo-l-thyronine supplementation on the cerebral neurotransmitters in hypothyroid rat offspring

الملخص EN

Introduction : 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.

Aim of the study : Assessment of the effect of 3, 5, 3 -triiodo-L-thyronine (T3) on changes in the cerebral neurotransmitters level and its possible mechanism in hypothyroid rat male offspring.

Materials and methods: 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 (Trtreated hypothyroid group) MMI was stopped and animal's offspring were received Ts (20 y.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 (TTj) and total triiodothyronine (TTs) at gestational day 10.

At the end of experiment, the offsptings were sacrificed and free thyroxine (FT4) and free triiodothyronine (FT3) in sera and neurotransmitters (dopamine, norepinephrine and serotonin) and Na ATPase activity were measured in the cerebral homogenate, Result : 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), norepinephrine (0.01 ± 0.001 mg /gvs 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 T3 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 < O.

Olrespectively) and Na', K -ATPase activity (3.87 ± 0.48 umol pi / mg protein) as compared with the hypothyroid group.

Conclusion : T3 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.