Presynaptic glycine receptors facilitate spontaneous glutamate release onto hilar neurons in the rat hippocampus |
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Authors: | Eun-Ah Lee Jin-Hwa Cho In-Sun Choi Michiko Nakamura Hye-Mi Park Jong-Ju Lee Maan-Gee Lee†‡ Byung-Ju Choi Il-Sung Jang‡ |
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Institution: | Department of Pharmacology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea; Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea; Brain Science &Engineering Institute, Kyungpook National University, Daegu, Republic of Korea |
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Abstract: | Although glycine receptors are found in most areas of the brain, including the hippocampus, their functional significance remains largely unknown. In the present study, we have investigated the role of presynaptic glycine receptors on excitatory nerve terminals in spontaneous glutamatergic transmission. Spontaneous EPSCs (sEPSCs) were recorded in mechanically dissociated rat dentate hilar neurons attached with native presynaptic nerve terminals using a conventional whole-cell patch recording technique under voltage-clamp conditions. Exogenously applied glycine or taurine significantly increased the frequency of sEPSCs in a concentration-dependent manner. This facilitatory effect of glycine was blocked by 1 μM strychnine, a specific glycine receptor antagonist, but was not affected by 30 μM picrotoxin. In addition, Zn2+ (10 μM) potentiated the glycine action on sEPSC frequency. Pharmacological data suggested that the activation of presynaptic glycine receptors directly depolarizes glutamatergic terminals resulting in the facilitation of spontaneous glutamate release. Bumetanide (10 μM), a specific Na-K-2C co-transporter blocker, gradually attenuated the glycine-induced sEPSC facilitation, suggesting that the depolarizing action of presynaptic glycine receptors was due to a higher intraterminal Cl? concentration. The present results suggest that presynaptic glycine receptors on excitatory nerve terminals might play an important role in the excitability of the dentate gyrus-hilus-CA3 network in physiological and/or pathological conditions. |
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Keywords: | glycine receptor hilar neurons hippocampus mossy fibers presynaptic facilitation sEPSCs |
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