Premium
Differential excitability and voltage‐dependent Ca 2+ signalling in two types of medial entorhinal cortex layer V neurons
Author(s) -
Egorov Alexei V.,
Heinemann Uwe,
Müller Wolfgang
Publication year - 2002
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2002.02197.x
Subject(s) - depolarization , neocortex , neuroscience , entorhinal cortex , pyramidal cell , afterhyperpolarization , chemistry , biophysics , membrane potential , apical dendrite , electrophysiology , dentate gyrus , voltage sensitive dye , hyperpolarization (physics) , hippocampal formation , cerebral cortex , biology , organic chemistry , nuclear magnetic resonance spectroscopy
The entorhinal cortex (EC) is a key structure in memory formation, relaying sensory information to the hippocampal formation and processed information to the neocortex. EC neurons in the deep layers modulate the transfer of sensory information by the superficial layers and the dentate gyrus, and form the output to the neocortex. Here we characterize two types of EC layer V neurons by their fluorescence morphology, electrophysiology and intracellular Ca 2+ signalling using intracellular recording and Ca 2+ imaging. Pyramidal neurons show, in response to depolarizing current pulses, regular firing with strong adaptation and a fast and medium afterhyperpolarization (AHP) which are separated by a depolarizing notch and, with hyperpolarizing current injection, a transient sag. Multipolar cells respond to depolarization with delayed firing with very weak adaptation and have no depolarizing notch between fast and medium AHP and no sag with hyperpolarization. The delayed firing was blocked by 30 µ m 4‐aminopyridine, indicating mediation by the D‐type potassium current. Subthreshold depolarization evoked membrane potential oscillations of 2–5 Hz in both cell types and an increase in [Ca 2+ ] i of 37 n m in pyramidal and 59 n m in multipolar neurons. Repetitive firing at 10 Hz for 30 s increased [Ca 2+ ] i in pyramidal and multipolar neurons by 194 and 295 n m , respectively. Differential temporal firing and Ca 2+ signalling suggest specific information processing and synaptic memory storage possibilities in these two layer V cell types of the EC.