Serotoninergic modulation of GABAergic synaptic transmission in developing rat CA3 pyramidal neurons |
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Authors: | Choi In-Sun Cho Jin-Hwa Kim Jung-Tak Park Eun-Joo Lee Maan-Gee Shin Hong-In Choi Byung-Ju Jang Il-Sung |
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Affiliation: | Department of Pharmacology, School of Dentistry, Kyungpook National University, Republic of Korea; Department of Pathology, School of Dentistry, Kyungpook National University, Republic of Korea; Department of Pharmacology, School of Medicine, Kyungpook National University, Republic of Korea |
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Abstract: | Serotoninergic modulation of GABAergic mIPSCs was investigated in immature (postnatal 12–16-days old) rat CA3 pyramidal neurons using a conventional whole-cell patch clamp technique. Serotonin or 5-hydroxytryptamine (5-HT) (10 μmol/L) transiently and explosively increased mIPSC frequency with a small increase in the current amplitude. However, 5-HT did not affect the GABA-induced postsynaptic currents, indicating that 5-HT acts presynaptically to facilitate the probability of spontaneous GABA release. The 5-HT action on GABAergic mIPSC frequency was completely blocked by 100 nmol/L MDL72222, a selective 5-HT3 receptor antagonist, and mimicked by mCPBG, a selective 5-HT3 receptor agonist. The 5-HT action on GABAergic mIPSC frequency was completely occluded either in the presence of 200 μmol/L Cd2+ or in the Na+-free external solution, suggesting that the 5-HT3 receptor-mediated facilitation of mIPSC frequency requires a Ca2+influx passing through voltage-dependent Ca2+channels from the extracellular space, and that presynaptic 5-HT3 receptors are less permeable to Ca2+. The 5-HT action on mIPSC frequency in the absence or presence of extracellular Na+ gradually increased with postnatal development. Such a developmental change in the 5-HT3 receptor-mediated facilitation of GABAergic transmission would play important roles in the regulation of excitability as well as development in CA3 pyramidal neurons. |
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Keywords: | 5-HT3 receptors CA3 pyramidal neurons GABAergic mIPSCs hippocampus ion permeability postnatal development |
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