Enes Akyuz, Züleyha Doğanyiğit, Eslem GÜNEY, Ayse Kristina POLAT

Sıçanlarda epilepsi modelinde vagus sinirinde norepinefrin taşıyıcılarının immünohistokimyası

Amaç: Epileptik nöbetler elektriksel aktivitenin aşırı ve kontrolsüz şekilde yayılmasının bir sonucu olarak ortaya çıkmaktadır. Yapılan çalışmalar epileptik nöbetlerin otonomik işlevi etkileyebileceğini bildirmiştir. Ancak moleküler mekanizma henüz tam olarak aydınlatılamamıştır. Vagus siniri (VS) tüm parasempatik sistem liflerinin %75’ini taşıdığından dolayı epilepsi patogeneziyle ilişkili otonomik merkezde büyük bir öneme sahiptir. Afferent duyusal lifleri beyin sapındaki ilişkili bölgelerdeki bağlantılar aracılığıyla sinapslar arası norepinefrin (NE) iletimini sağlamaktadır. Böylece, NE’nin nöbetler üzerinde baskılayıcı etkisi ve NE taşıyıcılarının (NET) nörotransmitter geri alımındaki görevi oluşabilir. Otonom sinir sisteminde görev alan nörotransmiterler ve ilgili taşıyıcıların moleküler düzeyde incelenmesi ilişkili mekanizmanın anlaşılmasına yardımcı olabilir. Bu çalışmada pentilentetrazol (PTZ) epilepsi modelinde NET ile ilişkili immünoreaktivitenin belirlenmesi amaçlanmıştır. Yöntem: Epileptik nöbetler Wistar sıçanlarında (280-380g) 28 gün boyunca PTZ [ilk 12 enjeksiyon 35 mg/ kg, intraperitoneal (I.P.) ve son enjeksiyon 50 mg/kg I.P.] uygulanarak indüklendi. Daha sonra VS torakal ve servikal kesitler açısından iki parça halinde diseke edildi. NET seviyeleri doku örnekleri üzerinde immünohistokimyasal boyama ile değerlendirildi. Bulgular: Erkek ve dişi deney gruplarının torakal vagus bölgesinde NET ifadesinin anlamlı olarak arttı. Servikal VS’de NET ekspresyonu epileptik erkek sıçanlarda önemli ölçüde artarken, epileptik dişi sıçanlarda kontrol gruplarına göre azaldı. Sonuç: Çalışmamız VS’de NET ifadesinin anlamlı bölgesel artışlarını ortaya koymuştur. NE regülasyonunda rol alan NET’in parasempatik sinirsel uyarım bozukluğu ile karakterize olabildiği düşünülmektedir. Gözlemlenen NET ifadesindeki değişiklikler epilepsi ile ilişkili otonom sinir sistemi işlev bozukluklarını etkileyebileceğine dair kanıtlar sunabilir.

Immunohistochemistry of norepinephrine transporters in the vagus nerve in a rat model of epilepsy

Objective: Epileptic seizures occur as a result of the excessive and uncontrolled spread of electrical activity. Studies have reported that epileptic seizures may affect the autonomic function. However, the main molecular mechanism has not been elucidated yet. Since the vagus nerve (VN) carries 75% of all parasympathetic autonomic system fibers, it is of great importance in the autonomic center associated with epilepsy pathogenesis. Afferent sensory fibers of the VN have connections to associated regions in the brainstem, providing norepinephrine (NE) transmission. Therefore, the suppressive effect of NE on seizures and the role of NE transporters (NET) in neurotransmitter reuptake may occur. Examining the neurotransmitters and related transporters in the autonomic nervous system at the molecular level may help to understand the related mechanism. In this study, we aimed to determine the NET-associated immunoreactivity in the VN in pentylenetetrazole (PTZ) epilepsy model. Methods: Epileptic seizures were induced in Wistar rats (280-380g) by administering PTZ [first 12 injections 35 mg/kg, intraperitoneal (I.P.) and last injection 50 mg/kg I.P.] for 28 days. Subsequently, the VN was dissected as two parts, in terms of the thoracic and cervical sections. The NET levels were evaluated by immunohistochemical staining on the tissue samples. Results: Expression of NETs in the thoracic VN region of the male and female experimental groups significantly increased. In the cervical VN, NET expression was significantly increased in epileptic male rats, while decreased in epileptic female rats compare to control groups. Conclusion: Our study may disclose significant regional enhancement in the NET immunoreactivity. It is assumed that NET, which plays a role in NE regulation, may be characterized by abnormal neural stimulation. The findings provide proof-of-concept that alterations in NET expression may affect the ANS dysfunctions associated with epilepsy.

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