NMDA receptor-mediated depolarizing after-potentials in the basal dendrites of CA1 pyramidal neurons

• Published in: Neuroscience research 2004-03, Vol.48 (3), p.325-333
• Main Authors: Enoki, Ryosuke, Kiuchi, Teppei, Koizumi, Amane, Sasaki, Go, Kudo, Yoshihisa, Miyakawa, Hiroyoshi
• Format: Article
• Language: English
• Subjects: Animals; Basal dendrites; Calcium Channel Blockers - pharmacology; Cells, Cultured; Dendrites - physiology; Dendrites - radiation effects; Depolarizing after-potential; Electric Stimulation - methods; Excitatory Postsynaptic Potentials - drug effects; Excitatory Postsynaptic Potentials - physiology; GABA Antagonists - pharmacology; Gallopamil - analogs & derivatives; Gallopamil - pharmacology; Hippocampus; Hippocampus - cytology; Lidocaine - analogs & derivatives; Lidocaine - pharmacology; Male; Model simulation; Models, Neurological; NMDA receptor; Patch-Clamp Techniques - methods; Pyramidal Cells - drug effects; Pyramidal Cells - physiology; Pyramidal Cells - radiation effects; Pyramidal neuron; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate - agonists; Receptors, N-Methyl-D-Aspartate - physiology; Sodium Channel Blockers - pharmacology; Statistics, Nonparametric; Valine - analogs & derivatives; Valine - pharmacology
• ISSN: 0168-0102; 1872-8111
• DOI: 10.1016/j.neures.2003.11.011

It was shown recently that the basal dendrites of cortical pyramidal neurons generate NMDA-spikes. In the present study, we made whole-cell recordings from hippocampal CA1 pyramidal neurons and examined whether NMDA receptor activation was involved in synaptic responses. At low input stimulus intensity, EPSPs with a fast decay time were induced. As the intensity of stimulation was increased in the presence of GABA receptor antagonists, a depolarizing after-potential (DAP) was generated in addition to a fast decaying potential. A DAP was never observed when the input was applied to the apical dendrites. The DAP was suppressed by hyperpolarization or by NMDA receptor antagonists, but not by Na +, K +, or Ca 2+ channel blockers. One possible mechanism is that the morphology of the basal dendrites favors DAP generation. A compartmental model simulation showed that synaptic inputs to thinner shorter dendrites generated a potential that resembled a DAP. Our study shows that a synaptic input to the basal dendrites of a hippocampal pyramidal neuron can generate a NMDA receptor-mediated potential in the presence of GABA receptor blockade.