In vivo demonstration of a late depolarizing postsynaptic potential in CA1 pyramidal neurons.
Previous studies have shown that GABA can have a depolarizing and excitatory action through GABA(A) receptors in mature CNS neurons in vitro. However, it remains unknown whether this occurs under physiological conditions. In this study, using intracellular recording and staining in vivo technique, we show a late depolarizing postsynaptic potential (L-PSP) in CA1 pyramidal neurons of adult Wistar rats under halothane anesthesia. This L-PSP was elicited in approximately 70% of the recorded neurons on stimulation of the Schaffer collaterals or the contralateral commissural path. The size of L-PSP was linearly correlated to the decay time constant but not the rising slope of the initial excitatory PSP (EPSP). Intravenous administration of the N-methyl-D-aspartate (NMDA) receptor blocker MK-801 and the GABA(A) receptor blocker picrotoxin significantly reduced the size of the L-PSP. The spine density and apical dendritic branching length of the neurons that displayed L-PSPs was significantly greater than those that do not. These results indicate that NMDA receptor and GABA(A) receptor-mediated depolarizing postsynaptic potentials can be revealed in CA1 pyramidal neurons of adult rats in vivo, supporting the physiological relevance of GABA(A)-mediated depolarization in normal neuronal information processing. The difference in electrophysiological properties and morphological features between neurons that display the L-PSP and the other neurons suggest that they might represent two different subtypes of CA1 pyramidal neurons.
Fan
Yuan
Y
Deptartment of Anatomy and Cell Biology, Indiana University School of Medicine, 635 Barnhill Dr., Indianapolis, IN 46202, USA.
Zou
Bende
B
Ruan
Yiwen
Y
Pang
Zhiping
Z
Xu
Zao C
ZC
D000818:Animals; D049229:Dendritic Spines / Q000378:metabolism / Q000648:ultrastructure; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology / Q000528:radiation effects; D018756:GABA Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology* / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D021621:Imaging, Three-Dimensional / Q000379:methods; D016014:Linear Models; D008297:Male; D008959:Models, Neurological; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000145:classification / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010852:Picrotoxin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009435:Synaptic Transmission / Q000502:physiology* / Q000528:radiation effects; D013997:Time Factors
D016291:Dizocilpine Maleate; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D010852:Picrotoxin