一般口演（Oral）

Oral Ion Channel Functions 一般口演イオンチャンネル機能

7月25日（木）9:00～9:15　第9会場（朱鷺メッセ　3F　306+307） 1O-09m1-1 Enhancement of neuronal excitability-mediated by Ih current reduction in CA1 neurons in a TBI rat Seyed Asaad Karimi（Karimi Seyed Asaad）^1,2,3,4，Narges Hosseinmardi（Hosseinmardi Narges）^3,4，Mohammad Sayyah（Sayyah Mohammad）⁵，Gholamhossein Meftahi（Meftahi Gholamhossein）⁶，Razieh Hajisoltani（Hajisoltani Razieh）^3,4，Mahyar Janahmadi（Janahmadi Mahyar）^3,4 ¹Department of Physiology and Neuroscience, Hamadan University of Medical Sciences, Hamadan, Iran ²Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran ³Neuroscience Research Center, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. ⁴Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran ⁵Department of Physiology and Pharmacology, Pasteur Institute of Iran, Tehran, Iran ⁶Neuroscience Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran Purpose: Alterations in the intrinsic electrophysiological properties and the contribution of hyperpolarization-activated cation current (Ih) to the TBI-induced hyperexcitability in CA1 pyramidal neurons was assessed. Methods: Using controlled cortical impact (CCI) as a model of traumatic brain injury (TBI), the intrinsic properties of pyramidal neurons were examined one week after TBI induction in rats. Whole-cell patch-clamp recordings were performed under current-clamp and voltage-clamp conditions, in the presence of fast synaptic blockers. Results: Findings showed that induction of TBI was associated with changes in intrinsic excitability of pyramidal neurons, evidenced by a significant increase in firing frequency and a significant decrease in the rheobase current (P < 0.05, respectively). Furthermore, the evoked firing rate and the action potential (AP) time to peak were significantly increased and decreased (P < 0.05, respectively). In TBI group, both the instantaneous (Iinst) and steady-state (ISS) Ih current amplitudes were significantly smaller than those in the control group (P < 0.05) and the sag ratio was significantly less than control values (P < 0.001). The Ih current density was also significantly decreased (P < 0.001). Conclusions: Findings indicated that TBI lead to the intrinsic hyperexcitability in CA1 pyramidal neurons and changes in Ih current could be, in part, one of the underlying mechanisms involved in this hyperexcitability. Key words: Controlled Cortical Impact; CA1 pyramidal neurons; Intrinsic Neuronal Excitability; Ih channel current; Traumatic Brain Injury		7月25日（木）9:15～9:30　第9会場（朱鷺メッセ　3F　306+307） 1O-09m1-2 クラスII ARFタンパク質の欠失はNav1.6の輸送不全により振戦を発症させる Tetsushi Sadakata（定方哲史）¹，Nobutake Hosoi（細井延武）³，Koji Shibasaki（柴崎貢志）²，Ayumu Konno（今野歩）³，Hirokazu Hirai（平井宏和）³，Yasuki Ishizaki（石崎泰樹）²，Teiichi Furuichi（古市貞一）⁴ ¹群馬大院医教育研究支援セ ²群馬大院医分子細胞生物 ³群馬大院医脳神経再生 ⁴東京理科大院理工応用生物科学 ADP-ribosylation factors (ARFs) are a family of small monomeric GTPases comprising six members categorized into three classes: class I (ARF1, 2, and 3); class II (ARF4 and 5); and class III (ARF6). In contrast to class I and III ARFs, which are the key regulators in vesicular membrane trafficking, the cellular function of class II ARFs remains unclear. In the present study, we generated class II ARF-deficient mice and found that ARF4^+/-/ARF5^-/- mice exhibited essential tremor (ET)-like behaviors. In vivo electrophysiological recordings revealed that ARF4^+/-/ARF5^-/- mice of both sexes exhibited abnormal brain activity when moving, raising the possibility of abnormal cerebellar excitability. Slice patch-clamp experiments demonstrated the reduced excitability of the cerebellar Purkinje cells (PCs) in ARF4^+/-/ARF5^-/- mice of both sexes. Immunohistochemical and electrophysiological analyses revealed a severe and selective decrease of pore-forming voltage-dependent Na+ channel subunit Nav1.6, important for maintaining repetitive action potential firing, in the axon initial segment (AIS) of PCs. Importantly, this decrease in Nav1.6 protein expression and the consequent tremors in ARF4^+/-/ARF5^-/- mice could be alleviated by the PC-specific expression of ARF5 using adeno-associated virus vectors. Taken together, our data demonstrate that the decreased expression of total class II ARF proteins in ARF4^+/-/ARF5^-/- mice, leading to a haploinsufficiency of ARF4 in the absence of ARF5, causes the disorganization of Nav1.6-containg AIS and hence the reduction of membrane excitability in PCs, resulting in the ET-like movement disorder. We suggest that class II ARFs play roles in targeting specific proteins, such as Nav1.6, to the AIS.

7月25日（木）9:30～9:45　第9会場（朱鷺メッセ　3F　306+307） 1O-09m1-3 T 型カルシウムチャネルはマウス海馬神経新生に関与する Yasushi Yabuki（矢吹悌），Jing Xu（許晶），Kohji Fukunaga（福永浩司）東北大院薬薬理学 T-type calcium channels are associated with the pathophysiology of epilepsy, pain and sleep. We recently developed the T-type calcium channel enhancer SAK3 (ethyl 8'-methyl-2',4-dioxo-2-(piperidin-1-yl)-2'H-spiro[cyclopentane-1,3'-imidazo [1,2-a] pyridine]-2-ene-3-carboxylate) using the whole-cell patch clamp technique. SAK3 can promote Cav3.1 and 3.3 T-type calcium channel currents in each channel overexpressed cells. SAK3 enhances acetylcholine (ACh) releases in the hippocampus and in turn improves cognitive impairments in olfactory bulbectomized (OBX) mice, those effects blocked by T-type calcium channel inhibitor NNC 55-0396 (12.5 mg/kg, i.p.). Here, we demonstrated the effect of SAK3 on hippocampal neurogenesis (Xu J and Yabuki Y et al., 2018. J Pharmacol Sci. 137(4):333-341). To investigate hippocampal neurogenesis, animals were treated with 5-Bromo-2´-Deoxyuridine (BrdU: 50 mg/kg, i.p.). Decreased number of BrdU positive cells was observed in the OBX hippocampal dentate gyrus (DG). Chronic SAK3 (0.5 mg/kg, p.o.) administration antagonized impaired hippocampal neurogenesis and then suppressed depressive-like behaviors seen in OBX mice. SAK3 (0.5 mg/kg, p.o.) administration also enhanced the intracellular calcium signaling, resulting in activating CREB/BDNF pathway in the OBX DG. These effects of SAK3 were completely blocked by pre-treatment with NNC 55-0396 (12.5 mg/kg, i.p.). Finally, both proliferation and survival in new generated cells were facilitated by SAK3 (0.5 mg/kg, p.o.) administration in the naive mouse DG and decreased in Cav3.1 null DG. To support our results, muscarinic and nicotinic ACh receptors mediate cell proliferation and survival in the hippocampal DG and T-type calcium channels may regulate adult neurogenesis directly and indirectly. Take together, SAK3 improves depression-like behaviors via T-type calcium channel stimulation in the hippocampus and T-type calcium channel activities may mediate the adult hippocampal neurogenesis.