Postnatal differentiation of firing properties and morphological characteristics in layer V pyramidal neurons of the sensorimotor cortex
Section snippets
Experimental procedures
Wistar rats (both sexes; Charles River) were deeply anaesthetized by means of ether vapour and decapitated, the brain was removed and placed in ice-cold artificial cerebrospinal fluid (ACSF) of the following composition (in mM): NaCl, 126; KCl, 3.5; CaCl2, 2; MgSO4, 2; NaH2PO4, 1.2; NaHCO3, 26; and glucose, 10 (pH 7.3–7.4) bubbled with 95% O2 and 5% CO2. Coronal slices, 400–450 μm-thick, were cut from dorsal frontoparietal cortex using a Vibratome, then transferred to an interface chamber and
Results
The firing characteristics of 217 putative pyramidal neurons recorded in immature rats aged between three and 22 days (P3–P6, 12; P7–P13, 38; P14–P17, 109; P18–P22, 56) and of 70 neurons recorded in adult rats, were evaluated.
Postnatal maturation of firing characteristics and associated properties
As previously reported by McCormick and Prince,[33]during the first postnatal week, neocortical pyramidal neurons were already able to generate trains of APs with a rather high firing frequency. However, in our observations, they displayed an homogeneous behaviour including an early decrease in firing frequency and a tendency to discharge, in response to moderately large depolarizing current pulses, with a limited train of APs. The rather stereotyped firing behaviour observed in early postnatal
Acknowledgements
The study was partially supported by CNR (CN94.00962.04) and by Paolo Zorzi Association for Neuroscience. The authors thank Mrs Maria Teresa Pasquali for editing assistance.
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