Long-term enhancement of synaptic transmission induced by veratridine in rat CA3 hippocampal neurons.
Veratridine is a neurotoxin that induces persistent activation of sodium channels in excitable cells. We investigated the effects of this toxin on excitatory synaptic transmission in CA3 neurons of juvenile rat hippocampus using whole-cell patch-clamp and field-potential recordings. The population spikes evoked by electrical stimulation of the mossy fiber were gradually enhanced after washout of veratridine (0.3 microM), but they were not enhanced by the co-application of veratridine and an N-methyl-D-aspartate (NMDA) receptor antagonist (D-APV, 30 microM). When a pipette solution contained QX-314 that antagonized the effect of veratridine in the recorded neuron, oscillatory membrane depolarization appeared in the early stage during bath-application of veratridine and gradually decreased in the late stage. After washout of veratridine, however, the oscillatory depolarization was gradually restored and maintained for at least 3 h. This oscillatory depolarization was also abolished by D-APV. We suggest that the activation of NMDA receptors is involved in the veratridine-induced long-lasting enhancement in the excitatory synaptic transmission in rat CA3 hippocampal neurons.
Department of Neurosurgery, Miyazaki Medical College, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan. mkohama@fc.miyazaki-med.ac.jp
M
M
Kohama
S
S
Miyahara
S
S
Nakano
S
S
Wakisaka
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D017774:Long-Term Potentiation / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D019599:Mossy Fibers, Hippocampal / Q000187:drug effects / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology*; D009924:Organ Culture Techniques; D017966:Pyramidal Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology; D014701:Veratridine / Q000494:pharmacology*
D018691:Excitatory Amino Acid Antagonists; D009498:Neurotoxins; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D015222:Sodium Channels; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D014701:Veratridine; D015763:2-Amino-5-phosphonovalerate