Presynaptic glycine receptors facilitate spontaneous glutamate release onto hilar neurons in the rat hippocampus.
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 microM strychnine, a specific glycine receptor antagonist, but was not affected by 30 microM picrotoxin. In addition, Zn(2+) (10 microM) 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 microM), 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.
Lee
Eun-Ah
EA
Department of Pharmacology, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
Cho
Jin-Hwa
JH
Choi
In-Sun
IS
Nakamura
Michiko
M
Park
Hye-Mi
HM
Lee
Jong-Ju
JJ
Lee
Maan-Gee
MG
Choi
Byung-Ju
BJ
Jang
Il-Sung
IS
D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018009:Receptors, Glycine / Q000378:metabolism*; D017661:Receptors, Presynaptic / Q000378:metabolism*
D018009:Receptors, Glycine; D017661:Receptors, Presynaptic; D018698:Glutamic Acid