Journal of Neuroscience, Vol 9, 2258-2271, Copyright © 1989 by Society for Neuroscience
Development of rat cerebellar Purkinje cells: electrophysiological properties following acute isolation and in long-term culture
PE Hockberger, HY Tseng and JA Connor
Department of Molecular Biophysics, AT&T Bell Laboratories, Murray Hill, New Jersey 07974.
The objectives of this study were 2-fold: (1) to characterize the
electrical properties of Purkinje cells (PCs) acutely isolated from rat
cerebella at different stages of development, and (2) to compare these
properties with those recorded from PCs grown in long-term culture. PCs
under both conditions were identified with the aid of cell-specific
immunocytochemical staining, and the electrical properties were analyzed
using whole-cell-recording techniques. PCs acutely isolated during late
embryonic and early postnatal periods displayed a progressive change in
electrical properties. Between embryonic days 20 and 22 (stage 1), PCs were
inexcitable, did not respond to glutamate, and displayed only small outward
currents under voltage clamp. During postnatal days 1-4 (stage 2), current
stimulation elicited nonovershooting action potentials, and small inward
and outward currents were evoked under voltage clamp. Glutamate application
depolarized the cells resulting in an increase in intracellular free
calcium measured with fura-2. Stage 3 and 4 cells spanned postnatal days
5-9 and 10-14, respectively, and the cells showed progressively larger
voltage-dependent conductances and greater sensitivity to glutamate. We
found no evidence for either spontaneous or complex spikes in PCs isolated
at any of these stages. In agreement with previous studies, we found that
PCs dissociated from postnatal rats did not survive well in culture. On the
other hand, PCs from embryonic rats cultured for 2-3 weeks in
high-potassium, serum-supplemented medium developed extensive dendritic
processes and excitability. Current stimulation or glutamate application
elicited depolarizing waveforms reminiscent of climbing fiber-evoked
responses in vivo. The results suggest that dendritic processes are
important in the generation of complex spikes and that PC excitability can
develop in the absence of the highly structured architecture of the intact
cerebellum.