Tiroit Hormonlarının Yüksek Frekanslı Uyarım ile Tetiklenen Sinaptik Gücün Depotansiyasyonu Üzerine Etkisi

Yıl 2021, , 369 - 374, 15.12.2021

Burak Tan Ercan Babur , Cem Süer Nurcan Dursun

https://doi.org/10.54005/geneltip.1036595

Öz

Önceki çalışma bulgularımız, normal tiroit hormon düzeylerinin sinaptik plastisitenin göstergeleri olan uzun dönemli güçlenme (UDG) ve uzun dönemli baskılanma (UDB) yanıtları arasındaki dengenin oluşmasında rol oynayabileceğini göstermektedir. Sinaptik plastisitenin bir diğer formu olan depotansiyasyon (DP) ise şu ana kadar bu bağlamda çalışılmamıştır. Bu çalışmada, tiroid hormonları ile sinaptik plastisite arasındaki ilişkiyi anlamak için, hipokampüse infüze edilen T4 ve T3 hormonlarının DP büyüklüğünü değiştirip değiştirmediği araştırılmıştır.

Deneyler, yüksek frekanslı uyarım (YFU) sırasında SF, T4 ve T3 infüze edilen ve düşük frekanslı uyarım (DFU) sırasında SF, T4 ve T3 infüze edilen 2 aylık Wistar albino erkek sıçanlardan oluşan (n=7/grup) 3 grup olarak gerçekleştirildi. Depotansiyasyonu indüklemek için, YFU kalıbı olarak 1 sn süreli 100 Hz frekanslı 4 tekrarlı uyarımı takiben 5 dk sonra, DFU kalıbı olarak 1 Hz frekanslı 900 pulse uyarım kullanıldı. Böylece uyarılan nöron havuzundaki sinapslarda hem yeni sinaps oluşumu hem de silinmesi elektriksel olarak tetiklendi ve kayıtlandı.

T4 hormonunun YFU sırasında uygulanmasının popülasyon spike (PS) genliğini kontrol grubuna göre değiştirdiği (p<0,001), DFU sırasında uygulanmasının ise etkilemediği (p>0,05) bulundu. T4 hormonunun YFU veya DFU sırasında uygulanmasının eksitatör postsinaptik potansiyel (EPSP) eğimindeki zamansal değişimlerinin ve T3 hormonunun YFU veya DFU sırasında uygulanmasının PS genliği ve EPSP eğimindeki zamansal değişimlerinin SF infüzyonu yapılanlar ile aynı olduğu bulundu.

Bu sonuçlar, T4’ün YFU sırasında uygulanmasının DP yanıtı üzerinde anlamlı bir etkiye sahip olduğunu, DFU sırasında T4 uygulanmasının ise, DP yanıtı üzerinde anlamlı bir etkiye sahip olmadığını düşündürmektedir.

Anahtar Kelimeler

Sinaptik plastisite, Depotansiyasyon, Tiroit hormonları, Hipokampüs

The Effect of Thyroid Hormones on Depotentiation of Synaptic Strengthening Which is Induced by High Frequency Stimulation

Öz

Our previous study findings showed that normal thyroid hormone levels may play a role in the balance between long-term potentiation (LTP) and long-term depression (LTD) that are indicative of synaptic plasticity. Depotentiation (DP), another form of synaptic plasticity, has not been studied in this context so far. In the present study, we aimed to learn the effect of infused T4 hormone on the depotentiation magnitude and the relationship between T4 and synaptic plasticity.

Experiments were performed in 3 groups of 2-month-old Wistar albino male rats (n=7/group) infused with SF, T4 and T3 during high frequency stimulation (HFS) or during low frequency stimulation (LFS). Depotentiation was induced by a HFS (100Hz,1 sec, 4 times), followed by LFS (900-pulse stimulation at 1 Hz). Thus, both synapse formation and deletion were electrically triggered and recorded in synapses of the stimulated neuron pool.

It was found that infusion of T4 during HFS decreased the PS amplitude compared to that control group (p <0.001), but infusion during LFS did not affect it (p> 0.05). It was found that the temporal changes in the EPSP slope of the infusion of T4 during HFS or LFS and the temporal changes in the PS amplitude and EPSP slope of the infusion of T3 during HFS or LFS were the same as the SF infusion.

These results suggested that the application of T4 during HFS have a significant effect on DP but the application of T4 during LFS does not seem to have a significant effect on DP.

Anahtar Kelimeler

Synaptic plasticity, Depotentiation, Thyroid hormones, Hippocampus

Kaynakça

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