Serotoninergic modulation of GABAergic synaptic transmission in developing rat CA3 pyramidal neurons.
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 micromol/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-HT(3) receptor antagonist, and mimicked by mCPBG, a selective 5-HT(3) receptor agonist. The 5-HT action on GABAergic mIPSC frequency was completely occluded either in the presence of 200 mumol/L Cd2+ or in the Na+-free external solution, suggesting that the 5-HT(3) receptor-mediated facilitation of mIPSC frequency requires a Ca2+ influx passing through voltage-dependent Ca2+ channels from the extracellular space, and that presynaptic 5-HT(3) 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-HT(3) receptor-mediated facilitation of GABAergic transmission would play important roles in the regulation of excitability as well as development in CA3 pyramidal neurons.
Choi
In-Sun
IS
Department of Pharmacology, School of Dentistry, Kyungpook National University, Republic of Korea.
Cho
Jin-Hwa
JH
Kim
Jung-Tak
JT
Park
Eun-Joo
EJ
Lee
Maan-Gee
MG
Shin
Hong-In
HI
Choi
Byung-Ju
BJ
Jang
Il-Sung
IS
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009924:Organ Culture Techniques; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D044406:Receptors, Serotonin, 5-HT3 / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D058827:Serotonin 5-HT3 Receptor Agonists; D058831:Serotonin 5-HT3 Receptor Antagonists; D013347:Subcellular Fractions; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
D015220:Calcium Channels; D044406:Receptors, Serotonin, 5-HT3; D058827:Serotonin 5-HT3 Receptor Agonists; D058831:Serotonin 5-HT3 Receptor Antagonists; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; D002118:Calcium